Category Archives: animals

Will the growing deer prion epidemic spread to humans? Why not?

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Helpful background reading: What’s the deal with prions?

A novel lethal infectious neurological disease emerged in American deer a few decades ago. Since then, it’s spread rapidly across the continent. In areas where the disease is found, it can be very common in the deer there.

Map from the Cornell Wildlife Health Lab.

Chronic wasting disease isn’t caused by a bacteria, virus, protist, or worm – it’s a prion, which is a little misshapen version of a protein that occurs naturally in the nervous systems of deer.

Chemically, the prion is made of exactly the same stuff as its regular counterpart – it’s a string of the same amino acids in the same order, just shaped a little differently. Both the prion and its regular version (PrP) are monomers, single units that naturally stack on top of each other or very similar proteins. The prion’s trick is that as other PrP moves to stack atop it, the prion reshapes them – just a little – so that they also become prions. These chains of prions are quite stable, and, over time, they form long, persistent clusters in the tissue of their victims.

We know of only a few prion diseases in humans. They’re caused by random chance misfolds, a genetic predisposition for PrP to misfold into a prion, accidental cross-contamination via medical supplies, or, rarely, from the consumption of prion-infected meat. Every known animal prions is a misfold of the same specific protein, PrP. PrP is expressed in the nervous system, particularly in the brain – so infections cause neurological symptoms and physical changes to the structure of the brain. Prion diseases are slow to develop (up to decades), incurable, and always fatal.

There are two known infectious prion diseases in people. One is kuru, which caused an epidemic among tribes who practiced funerary cannibalism in Papua New Guinea. The other is mad cow disease, also known as bovine spongiform encephalopathy (BSE) AKA Variant Creutzfeldt-Jakob disease, which was first seen in humans in 1996 in the UK, and comes from cows.

Chronic wasting disease (CWD)…

  • Is, like every other animal prion disease, a misfold of PrP. PrP is quite similar in both humans and deer.
  • Is found in multiple deer species which are commonly eaten by humans.
  • Can be carried in deer asymptomatically.

But it doesn’t seem to infect people. Is it ever going to? If a newly-emerged virus were sweeping across the US and killing deer, which could be spread through consuming infected meat, I would think “oh NO.” I’d need to see very good evidence to stop sounding the alarm.

Now, the fact that it’s been a few decades, and it hasn’t spread to humans yet, is definitely some kind of evidence about safety. But are we humans basically safe from it, or are we living on borrowed time? If you live in an area where CWD has been detected, should you eat the deer?

Sidenote: Usually, you’ll see “BSE” used for the disease in cows and “VCJ” for the disease in humans. But they’re caused by the same agent and this essay is operating under a zoonotic One Health kind of stance, so I’m just calling the disease BSE here. (As well as the prion that causes it, when I can get away with it.)

In short

The current version of CWD is not infectious to people. We checked. BSE showed that prions can spill over, and there’s no reason a new CWD variant will never do the same. The more cases there are, the more likely it is to spill over. That said, BSE did not spill over very effectively. It was always incredibly rare in humans. It’s an awful disease to get, but the chance of getting it is tiny. Prions in general have a harder time spilling over between species than viruses do. CWD might behave somewhat differently but probably will stay hampered by the species barrier.

Why do I think all of this? Keep reading.

North American elk (wapiti), which can carry CWD. This and the image at the top of the article are adapted from a photo from the Idaho Fish and Game department, under a CC BY 2.0 license.

Prions aren’t viruses

I said before that if a fatal neurological virus were infecting deer across the US, and showed up in cooked infected meat, my default assumption would be “we’re in danger.” But a prion isn’t a virus. Why does that matter?

Let’s look at how they replicate. A virus is a little bit of genetic material in a protein coating. You, a human, are a lot of genetic in a protein coating. When a virus replicates, it slips into your cells, and it hijacks your replication machinery to run its genes instead. Instead of all the useful-to-you tasks your genome has planned, the virus’s genome outlines its own replication, assembles a bunch more viruses, and blows up the factory (cell) to turn them loose into the world.

In other words, the virus using a robust information-handling system that both you and it have in common – the DNA → RNA → protein pipeline often called “the central dogma” of biology. To a first approximation, you can just add any genetic information at all into the viral genome, and as long as it doesn’t interfere with the virus’s process, whatever you add will get replicated in there too.

Prions do not work like this. They don’t tap into the central dogma. What makes them so fundamentally cool is that they replicate without touching the replication machinery that everything else alive uses – their replication is structural, like a snowflake forming. The host provides raw material in the form of PrP, and the prion – once it lands – encourages that material to shape in the right way for more to form atop it.

What this means is that you can’t encode arbitrary information into a prion. This isn’t just a factor – it’s not as though a prion runs on a separate “protein genome” we could decipher and then encode what we like into. The entire structure of the prion has to work together to replicate itself. If you made a prion with some different fold in it, that fold has to not just form a stable protein, but to pass itself along as well. They don’t have a handy DNA replicase enzyme to outsource to – they have to solve the problem of replication themselves, every time.

Prions can evolve, but they do it less – they have fewer free options, they’re more constrained than a virus would be in terms of changes that don’t interrupt the rest of the refolding process and that on top of that promulgate themselves.

This means that prions are slower to evolve than viruses. …I’m pretty sure, at least. It makes a lot of sense to me. The thing that this definitely means is that:

It’s very hard for prions to cross species barriers

PrP is a very conserved protein across mammals, meaning that all mammals have a version of PrP that’s pretty similar – 90%+ similarity.* But the devil lies in that 10%.

Prions are finely tuned – to convert PrP to a prion, it basically needs to be identical, or at least functionally identical, everywhere the prion works. It not just needs to be susceptible to the prion’s misfolding, it also needs to fold into something that itself can replicate. A few amino acid differences can throw a wrench in the works.

It’s clear that infectious prions can have a hard time crossing species barriers. It depends on the strain. For instance: Mouse prions convert hamster PrP.** Hamster prions don’t convert mouse PrP. Usually a prion strain converts its usual host PrP best, but one cat prion more efficiently converts cow PrP. In a test tube, CWD can convert human or cow PrP a little, but shows slightly more action with sheep PrP (and much more with, of course, deer PrP.)

This sounds terribly arbitrary. But remember, prion behavior comes down to shape. Imagine you’re playing with legos and duplo blocks. You can stack legos on legos and duplos on duplos. You can also put a duplo on top of a lego block. But then you can only add duplo blocks on top of that – you’ve permanently changed what can get added to that stack.

When we look at people – or deer, or sheep, etc – who are genetically resistant to prions (more on that later), we find that serious resistance can be conferred by single nucleic acid changes in the PrP gene. Tweak one single letter of DNA in the right place, and their PrP just doesn’t bend into the prion shape easily. If the infection takes, it proceeds slower – slow enough a person might die of old age before the prion would kill them.

So if a decent number of members of a species can be resistant to prion diseases, based on as little as one amino acid – then a new species, one that might have dozens of different amino acids in the PrP gene, is unlikely to be fertile ground for an old prion.

* (This is kind of weird given that we don’t know what PrP actually does – the name PrP just stands “prion protein” because it’s the protein that’s associated with prions, and we don’t know its function. We can genetically alter mice so that they don’t produce PrP at all, and they show slight cognitive issues but they’re basically fine. Classic evolution. It’s appendices all over again.)
** Sidebar: When we look at studies for this, we see that like a lot of pathology research, there's a spectrum of experiments on different points on the axis from “deeply unrealistic” to “a pretty reasonable simulacrum of natural infection”, like:

1. Shaking up loose prions and PrP in a petri dish and seeing if the PrP converts

2. Intracranial injection with brain matter (i.e. grinding up a diseased brain and injecting some of that nasty juice into the brain of a healthy animal and seeing if it gets sick)

3. Feeding (or some other natural route of exposure) a plausible natural dose of prions to a healthy animal and seeing if that animal gets sick

The experiments mentioned below are based on 1. Only experiments that do 3 actually prove the disease is naturally infectious. For instance, Alzheimer’s disease is “infectious” if you do 2, but since nobody does that, it’s not actually a contagious threat. That said, doing more-abstracted experiments means you can really zoom in on what makes strain specificity tick.

But prions do cross species barriers

Probably the best counterargument to everything above is that another prion disease, BSE, did cross the species barrier. This prion pulled off a balancing act: it successfully infected cows and humans at the same time.

Let’s be clear about one big and interesting thing: BSE is not good at crossing the species barrier. When I say this, I mean two things:

First, people did not get it often. While the big UK outbreak was famously terrifying, only around 200 people ever got sick from mad cow disease. Around 200,000 cows tested positive for it. But most cows weren’t tested. Researchers estimate that 2 million cows total in the UK had BSE, most of which were slaughtered and entered the food chain. These days, Britain has 2 million cows at any given time.

At first glance, and to a first approximation, I think everyone living in the UK for a while between 1985 and 1996 or so (who ate beef sometimes) must have eaten beef from an infected animal. That’s approximately who the recently-overturned blood donation ban in the US affected. I had thought that was sort of an average over who was at risk of exposure – but no, that basically encompassed everyone who was exposed. Exposure rarely leads to infection.

You’re more likely to get struck by lightning than to get BSE even if you have eaten BSE-infected beef.

Second, in the rare cases the disease takes, it’s slower. Farm cows live short lives, and the cows that died from BSE would have gotten old for the beef industry at 4-5 years post-exposure. They survived at most weeks or months after symptoms began. Humans infected with BSE, meanwhile, can harbor it for up to decades post-exposure, and live an average of over a year after showing symptoms.

I think both of these are directly attributable to the prion just being less efficient at converting human PrP – versus the PrP of the cows it was adapted to. It doesn’t often catch on in the brain. When it does, it moves extremely slowly.

But it did cross over. And as far as I can tell, there’s no reason CWD can’t do the same. Like viruses, CWD has been observed to evolve as it bounces between hosts with different genotypes. Some variants of CWD seem more capable of converting mouse PrP than the common ones. The good old friend of those who play god, serial passaging, encourages it.

(Note also that all of the above differs from kuru, which did cause a proper epidemic. Kuru spread between humans and was adapted for spreading in humans. When looking to CWD, BSE is a better reference point because it spread between cows and only incidentally jumped to humans – it was never adapted for human spread.)

How is CWD different from BSE?

BSE appears in very low, very low numbers anywhere outside the brains and spines of its victims. CWD is also concentrated in the brains, but also appears in the spines and lymphatic tissue, and to a lesser but still-present degree, everywhere else: muscle, antler velvet, feces, blood, saliva. It’s more systematic than BSE.

Cows are concentrated in farms, and so are some deer, but wild deer carry CWD all hither and yon. As they do, they leave it behind in:

  • Feces – Infected deer shed prions in their feces. An animal that eats an infected deer might also shed prions in its feces.
  • Bodies – Deer aren’t strictly herbivorous if push comes to shove. If a deer dies, another deer might eat the body. One study found that after a population of reindeer started regularly gnawing on each other’s antlers (#JustDeerThings), CWD swept in.
  • Dirt – Prions are resilient and can linger, viable, in soil. Deer eat dirt accidentally while eating grass, as well as on purpose from time to time and can be infected.
  • Grass – Prions in the soil or otherwise deposited onto plant tissue can hang out in living grass for a long time.
  • Ticks – One study found that ticks fed CWD prions don’t degrade the protein. If they’re then eaten by deer (for instance, during grooming), they could spread CWD. This study isn’t perfect evidence; the authors note that they fed the ticks a concentration of prions about 1000x higher than is found in infected deer blood. But if my understanding of statistics and infection dynamics is correct, that suggests that maybe 1 in 1000 ticks feeding on infected deer blood reaches that level of infectivity? Deer have a lot of ticks! Still pretty bad!

That’s a lot of widespread potentially-infectious material.

When CWD is in an area, it can be very common – up to 30% of wild deer, and up to 90% of deer on an infected farm. These deer can carry CWD and have it in their tissues for quite some time asymptomatically – so while it frequently has very visible behavioral and physical symptoms, it also sometimes doesn’t.

In short, there’s a lot of CWD in lots of places through the environment. It’s also spreading very rapidly. If a variant capable of infecting both deer and humans emerged, there would be a lot of chances for possible exposure.

Deer on a New Zealand deer farm. By LBM1948, under a CC BY-SA 4.0 license.

What to do?

As an individual

As with any circumstance at all, COVID or salmonella or just living in a world that is sometimes out to get you, you have to choose what level of risk you’re alright with. At first, writing this piece, I was going to make a suggestion like “definitely avoid eating deer from areas that have CWD just in case your deer is the one that has a human-transmissible prion disease.” I made a little chart about my sense of the relative risk levels, to help put the risk in scale even though it wasn’t quantified. It went like this:

Imagine a spectrum of risk of getting a prion disease. On one end, which we could call "don't do this", is "eating beef from an animal with BSE". Close to that but slightly less risky is "eating deer from an animal with CWD". On the other very safe end is "eating beef from somewhere with known active BSE cases". This entire model is wrong, though.

But, as usual, quantification turns out to be pretty important. I actually did the numbers about how many people ever got sick from BSE (~200) and how many BSE-infected cows were in the food chain (~2,000,000), which made the actual risk clear. So I guess the more prosaic version looks like this:

Remember that spectrum of risk? Well, all of these risks are infinitesimal. Worry about something else! Eating beef from an animal with BSE is still more dangerous than eating deer from an animal with CWD, which is more dangerous than eating beef from somewhere without known active BSE cases - but all of these are clustered very, very far on the safe side of the graph.

…This is sort of a joke, to be clear. There’s not a health agency anywhere on earth that will advise you to eat meat from cows known to have BSE, and the CDC recommends not eating meat from deer that test positive for CWD (though it’s never infected a human before.)

On top of that, the overall threat is still uncertain because what you’re betting on is “the chance that this animal will have had an as-of-yet undetected CWD variant that can infect humans.” There’s inherently no baseline for that!

We don’t know what CWD would act like if it spilled over. It might be more infectious and dangerous than other infectious prion diseases we’ve seen – remember, with humans, the sample size is 2! So if CWD is in your area and it’s not a hardship to avoid eating deer, you might want to steer clear. …But the odds are in your favor.

As a society

There’s not an obvious solution. The epidemic spreading among deer isn’t caused by a political problem, it’s from nature.

The US is doing a lot right: mainly, it is monitoring and tracking the spread of the disease. It’s spreading the word. (If nothing else, you can keep track of this by subscribing to google alerts for “chronic wasting disease”, and then pretty often you’ll get an email saying things like “CWD found in Florida for the first time” or “CWD found an hour from you for the first time.”) It is encouraging people to submit deer heads for testing, and not to eat meat from deer that test positive. The CDC, APHIS, Fish & Wildlife Service, and more are all aware of the problem and participating in tracking it.

What more could be done? Well, a lot of the things that would help a potential spillover of CWD look like actions that can be taken in advance of any threatening novel disease. There is research being done on prions and how they cause disease, better diagnostics, and possible therapeutics. All of these are important. Prion disease diagnosis and treatment is inherently difficult, and on top of that, has little overlap with most kinds of diagnosis or treatment. It’s also such a rare set of diseases that it’s not terribly well studied. (My understanding is that right now there are various kinds of tests for specific prion diseases – which could be adapted for a new prion disease – that are extremely sensitive although not particularly cheap or widespread.)

I don’t know a lot about the regulatory or surveillance situation vis-a-vis deer farms, or for that matter, much about deer farms at all. I do know that they seem to be associated with outbreaks, and heavy disease prevalence once there is an outbreak. That’s a smart area to an eye on.

If CWD did spill over, what would happens?

It will probably also take time to locate cases and identify the culprit, but given the aforementioned awareness and surveillance of the issue, it ought to take way less time than it took to identify the causative agent of BSE. Officials are already paying attention to deaths that could potentially be CWD-related, like neurodegenerative illnesses that kill young people.

First, everyone gets very nervous about eating venison for a while.

After that, I expect the effects will look a lot like the aftermath of mad cow disease. Mad cow disease, and very likely a hypothetical CWD spillover, would not be transmissible between people in usual ways – coughing, skin contact, fomites, whatever.

It is transmissible via unnatural routes, which is to say, blood transfusions. You might remember how people who’d spent over 6 months in Britain couldn’t donate blood in the US until 2022, a direct response to the BSE outbreak. Yes, the disease was extremely rare, but unless you can quickly and cheaply test incoming blood donations, a donor could donate blood to multiple people. Suppose some of them donate blood down the line. You’d have a chain of infection and a disease with a potentially decades-long incubation period. And remember, the disease is incurable and fatal. So basically, the blood donation system (and probably other organ donation) becomes very problematic.

That said, I don’t think it would break down completely. In the BSE case, lots of people in the UK eat beef from time to time – probably most people. But with a deerborne disease, I would guess that a lot of the US population could confidently declare that they haven’t eaten deer within the past, say, year or so (prior to a detected outbreak.) So I think there’d be panic and perhaps strain on the system but not necessarily a complete breakdown. Again, all of this is predicated on a new prion disease working like known human prion diseases.

Genetic resistance

One final fun fact: People who have a certain allele in the PrP gene – specifically, have the genotype PRNP 129M/V or V/V – are incredibly genetically resistant to known infectious prion diseases. If they do get infected, they survive for much longer.

It’s also not clear that this would hold true for a hypothetical CWD crossover to humans. But it is true for both kuru and BSE. It’s also partly (although not totally) protective against sporadic Creutzfeldt-Jakob disease.

If you’ve gotten a service like 23&me, maybe check out your data and see if you’re resistant to infectious prion diseases. Here’s what you’re looking for:

129M/V or V/V (amino acids), or G/G or A/G (nucleotides) – rs1799990

If you instead have M/M (amino acids) or A/A (nucleotides) at that site, you’re SOL at a higher but still very low overall risk.

Final thoughts

  • I think exercises like “if XYZ disease emerges, what will the ramifications and response be” are valuable. They lead to questions like “what problems will seem obvious in retrospect” and “how can we build systems now that will improve outcomes of disasters.” This is an interesting case study and I might revisit it later.

  • Has anyone reading this ever been struck by lightning? That’s the go-to comparison for things being rare. But 1 in 15,000 isn’t, like, unthinkably rare. I’m just curious.

  • No, seriously, what’s the deal with deer farms? I never think about deer farms much. When I think of venison, I imagine someone wearing camo and carrying a rifle out into a national forest or a buddy’s backyard or something. How many deer are harvest from hunting vs. farms? What about in the US vs. worldwide? Does anyone know? Tell me in the comments.

This essay was crossposted to LessWrong. Also linked at the EA Forums.

If you want to encourage my work, check out my Patreon. Today’s my birthday! I sure would appreciate your support.

Also, this eukaryote is job-hunting. If you have or know of a full-time position for a researcher, analyst, and communicator with a Master’s in Biodefense, let me know:

Eukaryote Writes Blog (at) gmail (dot) com

In the mean time, perhaps you have other desires. You’d like a one-off research project, or there’s a burning question you’d love a well-cited answer to. Maybe you want someone to fact-check or punch up your work. Either way, you’d like to buy a few hours of my time. Well, I have hours, and the getting is good. Hit me up! Let’s chat. 🐟

Woodblock print of swimming prawns

Eukaryote in Asterisk Magazine + New Patreon Per-post setup

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Eukaryote elsewhere

I have an article in the latest issue of Asterisk Magazine. After you get really deep into the weeds of invertebrate sentience and fish welfare and the scale of factory farming, what do you do with that information vis-a-vis what you feel comfortable eating? Here’s what I’ve landed on and why. Read the piece that Scott Alexander characterized as making me sound more annoying to eat with than I really am.

(Also check out the full piece of delightful accompanying art from Karol Banach.)

Check out the rest of the issue as well. Favorites include:

A new better Patreon has landed

This blog has a Patreon! Again! I’m switching from the old per month payment model to a new pay per post system, since this blog has not been emitting regular monthly updates in quite some time. So if you get excited when you see Eukaryote Writes Blog in your feed, and you want to incentivize more of that kind of thing, try this new and improved system for giving me money.

Here’s the link. Consider a small donation per post. Direct incentives: Lots of people are fans. I’m no effective charity but the consistent revenue does have a concrete and pleasant impact on my life right now, so I do really appreciate it.

It’s important to me that the things I write here are freely available. This will continue to be true! I might think of some short bits of content that will be patron-exclusive down the line, but anything major? Your local eukaryote is here to write a blog, not a subscription service. It’s in the name.

Helpful notes

  • To be clear, the payment will trigger per substantial new post. Updates of content elsewhere, metablogging like this, short corrections, etc, won’t count.
  • You can set a monthly limit in Patreon, even with the per-post model. For the record, I think it’s unlikely I’d put out more than 1-2 posts per month even in the long term future.
  • And of course, you can change your payment or unsubscribe at any old time you please.
Woodblock print of swimming prawns
Excerpt of Horse Mackerel (Aji) with Shrimp or Prawn, by Utagawa Hiroshige, ~1822-23. Public Domain.

Naked mole-rats: A case study in biological weirdness

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Epistemic status: Speculative, just having fun. This piece isn’t well-cited, but I can pull up sources as needed – nothing about mole-rats is my original research. A lot of this piece is based on Wikipedia.

When I wrote about “weirdness” in the past, I called marine invertebrates, archaea viruses, and Florida Man stories “predictably weird”. This means I wasn’t really surprised to learn any new wild fact about them. But there’s a sense in which marine invertebrates both are and aren’t weird. I want to try operationalizing “weirdness” as “amount of unpredictability or diversity present in a class” (or “in an individual”) compared to other members of its group.

So in terms of “animals your hear about” – well, you know the tigers, the mice, the bees, the tuna fish, the songbirds, whatever else comes up in your life. But “deep sea invertebrates” seems to include a variety of improbable creatures – a betentacled neon sphere covered in spikes, a six-foot long disconcertingly smooth and flesh-colored worm, bisexual squids, etc. Hey! Weird! That’s weird.

But looking at a phylogenetic tree, we see really quickly that “invertebrates” represent almost the entire animal tree of life.

 

Invertebrates represent most of the strategies that animals have attempted on earth, and certainly most of the animals on earth. Vertebrates are the odd ones out.

But you know which animals are profoundly weird, no matter which way you look at it? Naked mole rats. Naked mole-rats have like a dozen properties that are not just unusual, not just strange, but absolutely batshit. Let’s review.

1. They don’t age

What? Well, for most animals, their chance of dying goes up over time. You can look at a population and find something like this:

MoleRats1.jpg

Mole-rats, they have the same chance of dying at any age. Their graph looks like this:

20190519_133452.jpg

They’re joined, more or less, by a few species of jellyfish, flatworms, turtles, lobsters, and at least one fish.

They’re hugely long-lived compared to other rodents, seen in zoos at 30+ years old compared to the couple brief years that rats get.

2. They don’t get cancer

Cancer generally seems to be the curse of multicellular beings, but naked mole-rats are an exception. A couple mole-rats have developed cancer-like growths in captivity, but no wild mole-rat has ever been found with cancer.

3. They don’t feel some forms of pain

Mole-rats don’t respond to acid or capsaicin, which is, as far as I know, unique among mammals.

4. They’re eusocial

Definitely unique among mammals. Like bees, ants, and termites, naked mole-rats have a single breeding “queen” in each colony, and other “worker” individuals exist in castes that perform specific tasks. In an evolutionary sense, this means that the “unit of selection” for the species is the queen, not any individual – the queen’s genes are the ones that get passed down.

They’re also a fascinating case study of an animal whose existence was deduced before it was proven. Nobody knew about eusocial mammals for a long time. In 1974, entomologist Richard Alexander, who studied eusocial insects, wrote down a set of environmental characteristics he thought would be required for a eusocial mammal to evolve. Around 1981 and the next decade, naked mole-rats – a perfect match for his predictions – were found to be eusocial.

5. They don’t have fur

Obviously. But aside from genetic flukes or domesticated breeds, that puts them in a small unlikely group with only some marine mammals, rhinoceros, hippos, elephants, one species of boar, and… us.

nakedmoleratintube.gif

You and this entity have so much in common.

6. They’re able to survive ridiculously low oxygen levels

It uses very little oxygen during normal metabolism, much less than comparable-sized rodents, and it can survive for hours at 5% oxygen (a quarter of normal levels.)

7. Their front teeth move back and forth like chopsticks

I’m not actually sure how common this is in rodents. But it really weirded me out.

8. They have no regular sleep schedule

This is weird, because jellyfish have sleep schedules. But not mole-rats!

9. They’re cold-blooded

They have basically no ability to adjust their body temperature internally, perhaps because their caves tend to be rather constant temperatures. If they need to be a different temperature, they can huddle together, or move to a higher or lower level in their burrow.

All of this makes me think that mole-rats must have some underlying unusual properties which lead to all this – a “weirdness generator”, if you will.

A lot of these are connected to the fact that mole rats spend almost their entire lives underground. There are lots of burrowing animals, but “almost their entire” is pretty unusual – they don’t surface to find food, water, or (usually) mates. (I think they might only surface when digging tunnels and when a colony splits.) So this might explain (8) – no need for a sleep schedule when you can’t see the sun. It also seems to explain (5) and (9), because thermoregulation is unnecessary when they’re living in an environment that’s a pretty constant temperature.

It probably explains (6) because lower burrow levels might have very little oxygen most of the time, although there’s some debate about this – their burrows might actually be pretty well ventilated.

And Richard Alexander’s 12 postulates that would lead to a eusocial vertebrate – plus some other knowledge of eusociality – suggests that this underground climate, when combined with the available lifestyle and food source of a molerat, should lead to eusociality.

It might also be the source of (2) and (3) – people have theorized that higher CO2 or lower oxygen levels in burrows might reduce DNA damage or related to neuron function or something. (This would also explain why only mole-rats in captivity have had tumors, since they’re kept at atmospheric oxygen levels.) These still seem to be up in the air, though. Mole-rats clearly have a variety of fascinating biochemical tricks that are still being understood.

So there’s at least one “weirdness generator” that leads to all of these strange mole-rat properties. There might be more.

I’m pretty sure it’s not the chopstick teeth (7), at least – but as with many predictions one could make about mole rats, I could easily be wrong.

NakedMolerat.gif

To watch some naked mole-rats going about their lives, check out the Pacific Science Center’s mole-rat live camera. It’s really fun, if a writhing mass of playful otters that are also uncooked hotdogs sounds fun to you.

2019_05_19_14:15:48_Selection.png

Small animals have enormous brains for their size

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One thing that surprised me when working on How Many Neurons Are There was the number of neurons in the brains of very small animals.

Let’s look a classic measurement, the brain-mass:body-mass ratio.* Smarter animals generally have larger brain sizes for their body mass, compared to animals of similar size. Among large animals, humans have famously enormous brains for our size – the highest of any large animal, it seems. But as we look at smaller animals, that ratio goes up again. A mouse has a comparable brain:body-mass ratio to a human. Getting even smaller, insects have higher brain:body-mass ratios than any vertebrate we know of: more like 1 in 6.

But brain mass isn’t quite what we want – brains are mostly water, and there are a lot of non-neuron cells in brains. Conveniently, I also have a ton of numbers put together on number of neurons. (Synapse counts might be better, but those are hard to come by for different species. Ethology would also be interesting.)

And the trend is also roughly true for neuron-count:body-mass. Humans do have unusually high numbers of neurons per kilogram than other animals, but far, far fewer than, for instance, a small fish or an ant.

neuron-body-count-ratio-and-mass

If you believe some variation on one of the following:

  • Different species have moral worth in proportion to how many neurons they have
  • Different animal species have moral worth in proportion to how smart they are
  • Different species have moral worth in proportion to the amount of complex thought they can do
  • Different species have moral worth in proportion to how much they can learn**

…then this explanation is an indication that insects and other small animals have much more moral worth than their small size suggests.

How much more?

Imagine, if you will, a standard 5-gallon plastic bucket.

emptybucket

Now imagine that bucket contains 300,000 ants – about two pounds.*** Or a kilogram, if you prefer.

Imagine the bucket. Imagine the equivalent of a couple large apples inside it.

bucketwithants

A bucket. Two pounds of ants.

Those ants, collectively, have as many neurons as you do.

bucketandhuman

(Graphic design is my passion.)

You may notice that an adult human brain actually weighs more than two pounds. What’s going on? Simply, insect brains are marvels of miniaturization. Their brains have a panoply of space-saving tricks, and the physical cells are much smaller.

🐜🐜🐜

*Aren’t the cool kids using cephalization quotients rather than brain-mass:body-mass ratios? Yes, when it comes to measurements of higher cognition in vertebrates, cephalization is (as far as I’m aware) thought of as better. But there’s debate about that too. Referring to abilities directly probably makes sense for assessing abilities. I don’t know much about this and it’s not the focus of this piece, anyway.

**Yes, I know that only the first question is directly relevant to this piece, and that all of the others are different. I’m just saying it’s evidence. We don’t have a lot of behavioral data on small animals anyways, but I think we can agree there’s probably a correlation between brain size and cognitive capacity.

***Do two pounds of “normal-sized” ants actually fit in a five-gallon bucket? Yes. I couldn’t find a number for “ant-packing density” in the literature, but thanks to the valiant efforts of David Manheim and Rio Lumapas, it seems to be between 0.3 gallons (5 cups) and 5.5 gallons. It depends on size and whether ants pack more like spheres or more like blocks.

🐜🐜🐜

Suggested readings: Brian Tomasik on judging the moral importance of small minds (link is to the most relevant part but the whole essay is good) and on “clock speeds” in smaller animal brains, Suzana Herculano-Houzel on neuron count and intelligence in elephants versus humans,  How many neurons are there. (The last piece also contains most of the citations for this week. Ask if you want specific ones.)

This piece is crossposted to the Effective Altruism Forum.

Biodiversity for heretics

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Epistemic status: Not very confident in my conclusions here. Could be missing big things. Information gained through many hours of reading about somewhat-related topics, and a small few hours of direct research.

Summary: Biodiversity research is popular, but interpretations of it are probably flawed, in that they’re liable to confuse causation and correlation. Biodiversity can be associated with lots of variables that are rarely studied themselves, and one of these, not “biodiversity” in general, might cause an effect. (For example, more biodiverse ecosystems are more likely to include a particular species that has significant effects on its own.) I think “biodiversity” is likely overstudied compared to abundance, biomass, etc., because it’s A) easier to measure and B) holds special and perhaps undue moral consideration.

From what I was told, biodiversity – the number of species present in an environment – always seemed to be kind of magical. Biodiverse ecosystems are more productive, more stable over time, produce higher crop yields, and are more resistant to parasites and invaders. Having biodiversity in one place increases diversity in nearby places, even though diversity isn’t even one thing (forgive me for losing my citation here). Biodiverse microbiomes are healthier for humans. Biodiversity is itself the most important metric of ecosystem health. The property “having a suite of different organisms living in the same place” just seems to have really incredible effects.

First of all – quickly – some of what I was told isn’t actually true. More diverse microbiomes in bodies aren’t always healthier for humans or more stable. The effects of losing species in ecosystems varies a ton. More biodiverse ecosystems don’t necessarily produce more biomass.

That said, there’s still plenty of evidence that biodiversity correlates with something.

But: biodiversity research and its interpretations have problems. Huston (1997) introduced me to a few very concrete ways this can turn up misleading or downright inaccurate results.

Our knowledge about biodiversity’s effects on ecosystems comes from either experiments, in which biodiversity is manipulated in a controlled setting; or in observations of existing ecosystems. Huston identifies a few ways that these have, historically, given us bad or misleading data:

  1. Biotic or abiotic conditions, either in observations or experiments, are altered between groups. (E.g. you pick some sites to study that are less and more biodiverse, but the more-biodiverse sites are that way because they get more rainfall – which obviously is going to have other impacts)
  2. Species representing the “additional biodiversity” in experiments aren’t chosen randomly, they’re known to have some ecosystem function.
  3. Increasing the number of species increases the chance that one or a few of the added species will have some notable ecosystem effect on their own.

I’m really concerned about (3).

To show why, let’s imagine aliens who come to earth and want to study how humans work. They abduct random humans from across the world and put them in groups of various sizes.

Building walls

The aliens notice that the human civilizations have walls. They give their groups of abducted humans blocks and instruct them to build simple walls.

It turns out that larger groups of humans can build, on average, proportionally longer walls. The aliens conclude that wall-building is a property of larger groups of humans.

Building radios

The aliens also notice that human civilizations have radios. They give their groups of abducted humans spare electronic parts, and instruct them to build a radio.

Once again, it turns out that larger groups of humans are proportionally more likely to be able to build a radio. The aliens conclude that radio-building, too, is a property of large groups of humans.

The mistake the aliens are making is in assuming that wall- and radio-building are functions of “the number of humans you have in one place”. More people can build a longer simple wall, because there’s more hands to lift and help. But when it comes to building radios, a larger group just increases the chance that at least one human in the group will be an engineer.

To the aliens, who don’t know about engineers, “number of humans” kind of relates to the thing they’re interested in – they will notice a correlation – but they’re making a mistake by just waving their hands and saying that mostly only large groups of humans possess the intelligence needed to build a radio, perhaps some sort of hivemind.

Similarly, we’d make a mistake by looking at all the strange things that happen in diverse ecosystems, and saying that these are a magical effect that appears whenever you get large numbers of different plants in the same field. I wonder how often we notice that something correlates with “biodiversity” and completely miss the actual mechanism.

Aside from a specific species or couple of species in combination that have a particular powerful effect on ecosystems, what else might biodiversity correlate to that’s more directly relevant? How about abundance (the number of certain organisms of some kind present)? Or biomass (the combined weight of organisms)? Or environmental conditions, like the input of energy? Or the amount of biomass turnover, or the amount of predation, etc., etc.?

I started wondering about this while doing one of my several projects that relate to abundance in nature. We should still study biodiversity, sure. But the degree to which biodiversity has been studied compared to, say, abundance, has lead us to a world where we know there are 6,399 species of mammals, but nobody has any idea – even very roughly – how many mammals there are. Or how we’re pretty sure that there are about 7.7 million species of animals, plus or minus a few hundred thousand, which is a refinement of many previous estimates of the same thing – and then we have about two people (one of whom is wildly underqualified) trying to figure out how many animals there are at all.

It’s improving. A lot of recent work focuses on functional biodiversity. This is the diversity of properties of organisms in an environment. Instead of just recording the number of algae species in a coastal marine shelf, you might notice that some algae crusts on rocks, some forms a tall canopy, some forms a low canopy, and some grows as a mat. It’s a way of separating organisms into niches and into their interactions with the environment.

Functional diversity seems to better describe ecosystem effects than diversity alone (as described e.g. here). That said, it still leaves the door open for (3) – looking at functional diversity means you must know something about the ecosystem, but it’s not enough to tell you what’s causing the effect in and of itself.

To illustrate why:

Every species has some functional properties that separate it from other species – some different interactions, some different niche or physical properties, etc. We can imagine increasing biodiversity, then, as “a big pile of random variables.”

It turns out that when you start with a certain environment and slowly add or remove “a big pile of random variables”, that changes the environment’s properties. Who would have thought?

So is biodiversity instrumentally relevant to humans?

  1. There are sometimes solid explanations for why biodiversity itself might be relevant to ecosystems, e.g. the increased selection for species complementary over time theory.
  2. Biodiversity probably correlates to the things that studies claim it correlates to, including the ones that find significant environmental effects. I just claim that often, biodiversity is plausibly falsely described as the controlling variable rather than one of its correlates. (That said, there are reasons we might expect people to overstate its benefits – read on.)

If this is true, and biodiversity itself isn’t the driving force we make it out to be, why does everyone study it?

Firstly, I think biodiversity is easier to measure than, say, individual properties, or abundance. Looking at the individual properties and traits of each species in the environment is its whole own science, specific to that particular species and that particular environment. It would be a ridiculous amount of work.

But when we try to get the measure of an ecosystem without this really deep knowledge, we turn into the alien scientists – replacing a precise and intricate interaction with a separate but easier-to-measure variable that sort of corresponds with the real one.

What about studying one of the other ecosystem properties, like abundance? I’m guessing that in the modern research environment, you’d basically have to be collecting biodiversity data anyways.

Researcher: We found 255 beetles in this quadrant!

PI: What kind?

Researcher: You know. Beetles.

…And if you’re identifying everything you find in an environment anyways, it’s easier to just keep track of how many different things you find, rather than do that plus exhaustively search for every individual.

This is just speculation, though.

Secondly, a lot of people believe that species and ecosystems are a special moral unit (independent of any effects or benefits they might have on humans). That’s why people worry about losing the parasites of endangered species, or wonder if we shouldn’t damage biodiversity by eradicating diseases.

And… it’s hard to explain why this seems wrong to me, but I’ll try. I get it. Environmentalism is compelling and widespread. It was the background radiation of virtually almost every interaction with nature I had growing up. It was taken for granted that every drop of biodiversity was a jewel with value beyond measure, that endangered species were inherently worth going to great lengths to protect and preserve, that ecosystems are precariously balanced configurations that should be defended as much as possible from encroachment by humans. Under this lens, of course the number of species present is the default measurement – the more biodiversity preserved from human destruction, the more intricate and elaborate the ecosystem (introduced species excepted), the better.

And… doesn’t that seem a little limited? Doesn’t that seem like a sort of arbitrary way to look at huge parts of the world we live in? It’s not worth throwing out, but perhaps it deserves a little questioning. Where else could we draw the moral lines?

Personally, I realized my morality required me to treat animals as moral patients. This started with animals directly used by humans, but then got me re-examining the wild animals I’d been so fond of for so long.

Currently, I put individual animals and species in mostly-separated mental buckets. A species, a particular pattern instantiated by evolution acting on rocks and water over time, is important – but it’s important because it’s beautiful, like a fantastic painting made over decades by a long-dead artist. We value aesthetics, and interpretations, and certainly the world would be worse off without a piece of beauty like this one.

But an individual matters morally because it feels. It cares, it thinks, it feels joy, it suffers. We know because we are one, and because the same circuits and incentives that run in our brains also run in the brains of the cats, chickens, songbirds, insects, earthworms, whale sharks, and bristlemouths that we share this lonely earth with.

We might say that a species “suffers” or “is in pain”, the same way that a city “is in pain”, and we might mean several different things by that. We might say many of the individuals in the collective suffer. Or we might mean that the species is degraded somehow the way art is degraded – lessened in quantity, less likely to survive into the future, changing rapidly, etc. But it seems like a stretch to call that pain, in the way that being eaten alive is pain.

Obviously, at some point, you have to make trade-offs over what you care about. I don’t have my answers worked out yet, but for now, I put a lot more value on the welfare of individual animals than I used to, and I care less about species.

I don’t expect this viewpoint to become widespread any time soon. But I think it’s possible that the important things in nature aren’t the ones we’ve expected, and that under other values, properties like abundance and interactions deserve much more attention (compared to biodiversity) than they have now.

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[OPEN QUESTION] Insect declines: Why aren’t we dead already?

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One study on a German nature reserve found insect biomass (e.g., kilograms of insects you’d catch in a net) has declined 75% over the last 27 years. Here’s a good summary that answered some questions I had about the study itself.

Another review study found that, globally, invertebrate (mostly insect) abundance has declined 35% over the last 40 years.

Insects are important, as I’ve been told repeatedly (and written about myself). So this news begs a very important and urgent question:

Why aren’t we all dead yet?

This is an honest question, and I want an answer. (Readers will know I take catastrophic possibilities very seriously.) Insects are among the most numerous animals on earth and central to our ecosystems, food chains, etcetera. 35%+ lower populations are the kind of thing where, if you’d asked me to guess the result in advanced, I would have expected marked effects on ecosystems. By 75% declines – if the German study reflects the rest of the world to any degree – I would have predicted literal global catastrophe.

Yet these declines have been going on for apparently decades apparently consistently, and the biosphere, while not exactly doing great, hasn’t literally exploded.

So what’s the deal? Any ideas?

Speculation/answers welcome in the comments. Try to convey how confident you are and what your sources are, if you refer to any.

(If your answer is “the biosphere has exploded already”, can you explain how, and why that hasn’t changed trends in things like global crop production or human population growth? I believe, and think most other readers will agree, that various parts of ecosystems worldwide are obviously being degraded, but not to the degree that I would expect by drastic global declines in insect numbers (especially compared to other well-understood factors like carbon dioxide emissions or deforestation.) If you have reason to think otherwise, let me know.)

Sidenote: I was going to append this with a similar question about the decline in ocean phytoplankton levels I’d heard about – the news that populations of phytoplankton, the little guys that feed the ocean food chain and make most of the oxygen on earth, have decreased 40% since 1950.

But a better dataset, collected over 80 years with consistent methods, suggests that phytoplankton have actually increased over time. There’s speculation that the appearance of decrease in the other study may have been because they switched measurement methods partway through. An apocalypse for another day! Or hopefully, no other day, ever.

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How many neurons are there?

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Image from NOAA, in the public domain.

Last updated on March 16, 2018. I just finished a large project trying to estimate that. I’ve posted it on its own page here. Here’s the abstract:

We estimate that there are between 10^23 and 10^24 neurons on earth. Most of this is distributed roughly evenly among small land arthropods, fish, and nematodes, or possibly dominated by nematodes with the other two as significant contenders. For land arthropods, we multiplied the apparent number of animals on earth by mostly springtail-sized animals, with some small percentage being from larger insects modeled as fruit flies. For nematodes, we looked at studies that provide an average number of nematodes per square meter of soil or the ocean floor, and multiplied them by the number of neurons in Caenorhabditis elegans, an average-sized nematode. For fish, we used total estimates of ocean fish biomass, attributed some to species caught by humans, and used two different ways of allocating the remaining biomass. Most other classes of animal contribute 10^22 neurons at most, and so are unlikely to change the final analysis. We neglected a few categories that probably aren’t significant, but could conceivably push the estimate up.

Using a similar but less precise process based on evolutionary history and biomass over time, we also estimate that there have been between 10^32 and 10^33 neuron-years of work over the history of life, with around an order of magnitude of uncertainty.

Male dairy calves, male chicks, and relative suffering from animal foods

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Or: Do “byproduct” animals of food animal production significantly affect estimates of comparative suffering caused by those foods? No.

[Image adapted from this image by Flickr user Sadie_Girl, under a CC BY-SA 2.0 license.]

See, relatedly: What happens to cows in the US?

Short version

There’s a shared belief in animal-welfare-oriented effective altruism that eggs and chicken meat cause a great deal more suffering than beef or dairy (1). You can make big strides towards reducing the amount of suffering caused in your diet by eating fewer eggs and chicken, even if you don’t go fully vegetarian or vegan.

Julia Galef, Brian Tomasik, and William MacAskill have made different versions of this calculation, with different metrics, and have come to the same conclusion. These three calculations include only the animal used directly for production. (Details about the calculations and my modifications are in the long version below.) But the production of several kinds of animal product require bringing into existence animals that aren’t used for that product – like male calves born to lactating dairy cows, or male chicks born when producing egg-laying hens. I wondered if including these animals would significantly change the amount of suffering in various animal foods.

It turns out that even accounting for these other animals indirectly created during production, the amount of suffering relative to other animal foods doesn’t change very much. If you buy the premises of these quantitative ethical comparisons, beef and dairy make so much product using so few animals that they’re still 1-3 orders of magnitude better than eggs or chicken. Or rather, the message of “eat less chicken” and “if you’re going to eat animal products, eat dairy and beef” still makes sense even if we account for the maximum number of other animals created incidental to production of each food animal. I’m going to call these the “direct and incidental animals” (DIA) involved in a single animal’s worth of product.

The question is complicated by the fact that “incidental” animals still go into another part of the system. Day-old male chicks are used for pet and livestock food, and male dairy calves are raised for meat.

Given that these male calves are tied to dairy production, it seems unlikely that production of dairy and meat is what it would be if they weren’t connected. For instance, if there is less demand for dairy and thus fewer male dairy calves, it seems like one of the following should happen:

  1. No change to meat calf supply, less meat will be produced (DIA estimates seem correct)
  2. Proportionally more meat calves will be raised (original estimates seem correct)
  3. Something between the above (more likely)

Reframed: It depends whether demand for dairy increases the meat supply and makes it less profitable to raise meat cows, or whether demand for meat makes it more profitable to raise dairy cows, or both. I’m not an economist and don’t go into which one of these is the case. (I tried to figure this out and didn’t make much headway.) That said, it seems likely that the actual expected number of animal lives or days of suffering is somewhere between the initial numbers and my altered values for each source.

The most significant change I find from the original findings suggest that meat cows cause a fair bit more suffering over a longer period of time than the original calculations predict, only if demand for meat is significantly propping up the dairy industry. But even if that’s true, the suffering caused by beef is a little smaller than that caused by pork, and nowhere near as much as smaller animals.

Modifications to other estimates including direct and incidental animals (DIA)

Tomasik’s original estimate DIA Tomasik’s estimate Galef’s orginal estimate DIA Galef’s estimate
Milk 0.12 equivalent days of suffering caused per kg demanded 0.14 equivalent days of suffering caused per kg demanded 0.000057 max lives per 1000 calories of milk 0.00013 max lives per 1000 calories of milk
Beef 1.9 max equivalent days of suffering caused per kg demanded 4.74 max equivalent days of suffering caused per kg demanded 0.002469 max lives per 1000 calories 0.0029 max lives per 1000 calories
Eggs 110 equivalent days of suffering caused per kg demanded 125 equivalent days of suffering caused per kg demanded 0.048485 lives per 1000 calories 0.048485 lives per 1000 calories

That’s basically it. For a little more info and how I came to these conclusions, read on.

Longer version

On the topic of effectively helping animals, one thing I’ve heard a few times is that eating dairy and beef aren’t terribly harmful, since they come from such large animals that a serving of beef or milk is a very small part of the output of the animal. On the other hand, chickens are very small – an egg is a day’s output of an animal, and a family can eat an entire chicken in one dinner. Compare that with the fact that most chickens are raised in extremely unnatural and unpleasant conditions, and you have a framework for directly comparing the suffering that goes into different animal products.

This calculation has been made by three people I’m aware of – Brian Tomasik on his website, William MacAskill in his book Doing Good Better, and Julia Galef on her blog. The organization One Step for the Animals also recommends people stop eating chickens, on these grounds, but I didn’t find a similar breakdown on their website after a few minutes of looking. It’s still worth checking out, though. (Did you know chicken consumption, in pounds/year, has surpassed beef consumption and is still climbing, but only over the last 20 years?)

Galef compares calories per life. She includes the male chicks killed for each egg-laying hen.

Tomasik looks at “days of suffering caused per kg demanded”.

Macaskill briefly examines three factors: the number of animal years and lives that go into a year of eating in the average omnivorous American diet, and also numerical “quality of life” estimates from Bailey Norwood. (He doesn’t combine these factors numerically so much as use them to establish a basis for recommending people avoid chicken. I didn’t do an in-depth analysis of his, but safe to say that like the others, adding in other animal lives doesn’t seem to change his conclusions significantly.)

With pigs and meat chickens, the case is straightforward – both sexes are raised for meat, and suppliers breed animals to sell them and retain enough to continue breeding. The aged animals are eventually slaughtered as meat as well.

But only female hens lay eggs. Meat chickens and egg chickens raised at scale in the USA are two different breeds, so when a breeder produces laying hens, they wind up with more male chicks than are needed for breeding. Similarly, dairy cows have to give birth to a calf every season they produce milk. The average dairy cow gives 2.4 calves in her lifetime, and slightly less than 1.2 of those are male. The male egg chicks and male dairy calves are used for meat.

Aged dairy cows and egg-laying chickens are also sold as meat. “Spent hens” that are no longer commercially profitable, at 72 weeks old, are sold for ‘processed chicken meat’. (Other sources claim pet food or possibly just going to landfills. Pet food sounds reasonable, but landfills seem unlikely to me, at least for large operations.) There aren’t as many of these as either cows or chickens raised directly for meat, so they’re a comparatively small fraction, but they’re clearly still feeding into the meat system.

🐔

When talking about this, we quickly run into some economic questions, like “perhaps if the demand for dairy dropped, the meat industry would start raising more calves for meat instead?”

My intuition says it ought to shake out one way or the other – either decreasing demand for dairy cows results in the price of meat going up, or decreasing demand for meat results in demand for dairy cows going down.

In the egg case, male chicks aren’t literally put in a landfill, they’re ground and sold for pet food. Without this otherwise unused source of protein, would pet food manufacturers increase demand for some other kind of meat? It seems possible that both this would happen and that the price of pet food would increase. Then, maybe less would be bought to make up for the difference, at least in the long term – cheap pet food must be somewhat inelastic, at least in the short term?

My supply and demand curves suggest that both demand should decline and price should increase. That said, we’re leaving the sphere of my knowledge and I don’t know how to advise you here. For the moment, I’m comfortable folding in both animals produced in the supply chain for a product, and animals directly killed or used for a product. But based on the economic factors above, these still don’t equate to “how many animal lives / days are expected to be reduced in the long term by avoiding consumption of a given product.”

At the most, though, dairy cows bring an extra 1.2 meat cow into existence, meat cows bring an extra .167 dairy cow,  and each egg-laying hen brings an extra 1 male chicken that is killed around the first day. These are the “direct and incidental animals” created for each animal directly used during productive.

 

Some notes on the estimates below:

I ignored things like fish and krill meal that go into production. Tomasik notes that 37% of the global fish harvest (by mass) is ground and used for animal feed for farmed fish, chickens, and pigs. But this seems to be mostly from wild forage fish, not farmed fish, and wild populations are governed by a different kind of population optimum – niches. We’d guess that each fish removed from the environment frees up resources that will be eaten by, on average, one new fish. (Of course, populations we’re fishing seem to be declining, so something is happening, but it’s certainly not one-to-one.)

I also only looked at egg-laying chickens, meat cows, and dairy cows. This is because pork and other industries aren’t sex-segregated – all babies born are raised for the same thing. A few will be kept aside and used to produce more babies, but even the breeding ones will eventually be turned into meat. The amount of days these animals live probably affect Tomasik’s calculations somewhat, but the breeding animals are still the minority.

I also didn’t include a detailed analysis because if you’re concerned about animal welfare, you probably already don’t eat veal. (I’m going to assert that if you want to eat ethically treated food, avoid a meat whose distinguishing preparation characteristic is “force-feed a baby”.) Veal is a byproduct of the dairy industry, but a minority of the calves. Foie gras does have a multiplier effect because female geese don’t fatten up as much, and are killed early, so for each goose turned into foie gras, another goose is killed young.

Old dairy cows and laying hens are used for meat, but it’s a minority of the meat production. I didn’t factor this in. See What happens to cows in the US for more on cows.

Modifications to other estimates including direct and incidental animals (DIA)

Tomasik’s original estimate DIA Tomasik’s estimate Galef’s orginal estimate DIA Galef’s estimate
Milk 0.12 equivalent days of suffering caused per kg demanded 0.14 equivalent days of suffering caused per kg demanded 0.000057 max lives per 1000 calories of milk 0.00013 max lives per 1000 calories of milk
Beef 1.9 max equivalent days of suffering caused per kg demanded 4.74 max equivalent days of suffering caused per kg demanded 0.002469 max lives per 1000 calories 0.0029 max lives per 1000 calories
Eggs 110 equivalent days of suffering caused per kg demanded 125 equivalent days of suffering caused per kg demanded 0.048485 lives per 1000 calories 0.048485 lives per 1000 calories

DIA modifications to Tomasik’s estimate

(Days of equivalent suffering / kg)

To adjust this estimate, I added the extra “equivalent days of suffering caused per kg demanded” for the other animals:

Egg-laying chickens
(4 suffering per day of life in egg-laying chickens * 501 days of life) + 1 * (3 suffering per days of life in meat chickens * 1 day of life) / 16 kg of edible product over life of egg-laying chicken = 125 max equivalent days of suffering caused per kg demanded (vs 110)

Dairy cows
(2 suffering per day of life in milk cows * 1825 days of life) + 1.2 * (1 suffering per day of life in meat cows * 395 days of life) / 30000 kg of edible product over life of dairy cow = 0.14 max equivalent days of suffering caused per kg demanded (vs 0.12)

Meat cows
(1 suffering per day of life in meat cows * 395 days of life) + 0.167 * (2 suffering per day of life in dairy cows * 1825 days of life) / 212 kg of edible product over life of meat cow = 4.74 max equivalent days of suffering caused per kg demanded (vs 1.9)

The meat cow number is the only very different one here.

DIA modifications to Galef’s estimate

I adjusted this by adding other lives to Galef’s estimate of lives per 1000 calories:

Egg-laying chicken
Galef included this in her calculation of 0.048485 lives per 1000 calories of eggs.

Dairy cows
[0.000057 lives per 1000 calories of milk] * 2.2 = 0.00013 max lives per 1000 calories of milk
[0.000075 lives per 1000 calories of cheese] * 2.2 = 0.00017 max lives per 1000 calories of cheese

Meat cows
[0.002469 lives per 1000 calories of beef] * 1.167 = 0.0029 max lives per 1000 calories of beef

Other economic notes

I’m hoping someone who knows more here will be able to make use of the information I found.

The number of meat cows in the US has been broadly decreasing since 1970. The number of dairy cows has also been decreasing since at least 1965, but dairy consumption is increasing, because those cows are giving far more milk.

When dairy prices drop, dairy farmers are known to kill some of their herds and sell them for meat, leading to a drop in meat prices.

We would also expect dairies and beef farms to compete with each other for some of the same resources, like land and feed.

A friend wondered whether dairy steers are much smaller than beef cows, so if shifting the same volume of meat production to these steers would mean more animal lives. It turns out that dairy steers and beef cows are about the same weight at slaughter.

(1) With fish perhaps representing much more suffering than eggs or chickens, and other large meat sources like pigs somewhere in the middle.)

 

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What happens to cows in the US?

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(Larger version. Image released under a CC-BY SA 4.0 license.)

There are 92,000,000 cattle in the USA. Where do they come from, what are they used for, and what are their ultimate fates?

I started this as part of another project, and was mostly interested in what happens to the calves of dairy cows. As I worked, though, I was astonished that I couldn’t easily find this information laid out elsewhere, and decided to publish it on its own to start.

Note: Numbers are not exactly precise, and come from a combination of raw data from 2014-2016 and guesswork. Also, the relative sizes on the graph (of arrows and boxes) are not accurate – they’re hand-sized based on eyeballing the numbers and the available settings in yEd. I’m a microbiologist, not a graphic designer, what do you expect? If that upsets you, try this version, which is also under a CC-BY SA 4.0 license. If you want to make a prettier or more accurate version, knock yourself out.

There are some changes from year to year, which might account for small (<5%) discrepancies. I also tried to generalize from practices used on larger farms (e.g. <1,000 cow operations), which make up a minority of the farms, but house a majority of the cattle.

In the write-up, I try to clearly label “male cattle” and “female cattle” or “female cows” when relevant, because this confused me to no end when I was gathering data.

Let’s start with dairy cows. There are 9,267,000 female cows actively giving milk this season (“milk cows”) in the USA. For a cow to give milk, it has to be pregnant and give birth. That means that 9,267,000 calves are born to milk cows every year.

Almost half of these are female. Most milk cows are impregnated at around 2 years with artificial insemination. There’s a huge market in bull sperm, and 5% of the sperm sold in the US is sex-selected, meaning that 90% of the sperm in a given application is one sex. Dairies are mostly interested in having more female cows, so it seems like 2.25% of the milk cow calves that would have been male (because of chance) are instead female (because of this technology).

The female calves almost all go back into being milk cows. The average dairy cow has 2.4 lactation periods before she’s culled, so she breeds at a little over her replacement rate. I’m actually still not 100% certain where that 0.2-nd female calf goes, but dairies might sell extra females to be beef cattle along with the males.

The 2,755,000 milk cows that are culled each year are generally turned into lean hamburger. They’re culled because of infection or health problems, or age and declining milk volume. They’re on average around 4 years old. (Cows can live to 10 years old.)

Male calves are, contrary to some claims, almost never just left to die. The veal industry exists, in which calves are kept in conditions ranging from “not that different from your average cow’s environment” to “absolutely terrible”, and are killed young for their meat. It seems like between 450,000 and 1,000,000 calves are killed for veal each year, although that industry is shrinking. I used the 450,000 number.

Some of the male calves are kept and raised, and their sperm is used to impregnate dairy cows. This article describes an artificial insemination company, which owns “1,700 dairy and beef bulls, which produce 15 million breeding units of semen each year.” That’s about 1 in 1,000, a minuscule fraction of the male calves.

The rest of those male calves, the dairy steers, are sold as beef cattle. After veal calves, we have 3,952,000 remaining male calves to account for. They make up 14% of the beef supply of the 30,578,000 cattle slaughtered annually. From those numbers, we’d guess that 4,060,000 dairy steers are killed yearly – and that’s close enough to the above estimate that I think we’ve found all of our male calves. That’s only a fraction of the beef supply, though – we’ll now turn our attention to the beef industry.

We imported 1,980,000 cattle from Canada and Mexico in 2015, mostly for beef. We also export a few, but it’s under 100,000, so I left if off the chart.

Most beef cows are bred on calf-cow operations, which either sell the calves to feedlots or raises calves for meat directly. To replace their stock, they either keep some calves to breed more cows, or buy them from seedstock operations (which sell purebred or other specialty cattle.) Based on the fact that 30,578,000 cattle are slaughtered annually (and we know how some of them are already killed), and that cattle are being bred at the replacement rate, it seems like each year, calf-cow operations generate 21,783,000 new calves.  There’s a lot of variation in how beef cattle are raised, which I’m mowing over in this simplified graph. In general, though, they seem to be killed at between 1.5 and 3 years old.

Of course, calf-cow operations also need breeding cattle to keep the operation running, so while some of those cows are raised only for meat, some are also returned to the breeding pool. (Seedstock operations must be fairly small – under 3% of cattle in the US are purebred – so I think calf-cow operations are the majority worth examining.) Once they’re no longer productive breeders, breeding animals are also culled for beef.

This article suggests that 14-15% of cows are culled annually, I think on cow-calf operations that raise cows for slaughter themselves (although possibly only on smaller farms). If that’s the case, then each year, they must create about 14.5% more calves than are used raised only for meat. This suggests that 21,783,000 cattle born to calf-cow operations are raised for meat, and the remaining 2,759,000 calves which will go back into breeding each year. These will mostly be females – there seems to be a 1:15-25 ratio of males to females on calf-cow operations – so disproportionately more males will go directly to beef.

By adding up the bottom numbers, we get ~30,600,000 cattle slaughtered per year. In terms of doing math, this is fortunate, because we also used that number to derive some of the fractions therein. We can also add up the top numbers to get 33,030,000 born, which is confusing. If we take out the 450,000 veal calves and the 1,980,000 imported calves, it drops back to the expected value, which I think means I added something together incorrectly. While I’m going to claim this chart and these figures are mostly right, please do let me know if you see holes in the math. I’m sure they’re there.

“Wow, Georgia, I’m surprised, I really thought this was going to veer off into the ethics of the dairy industry or something.”

Ha ha. Wait for Part 2.

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Beespotting on I-5 and the animal welfare approach to honey

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The drive from Seattle to San Francisco along I-5 is a 720-mile panorama of changing biomes. Forest, farmland, and the occasional big city get very gradually drier, sparser, flatter. You pass a sign for the 45th parallel, marking equidistance between the equator and the North Pole. Then the road clogs with semis chugging their way up big craggy hills, up and up, and then you switch your foot from the gas to the brake and drop down the hills into more swathes of farmland, and more intense desert, with only the very occasional tiny town to get gas and bottles of cold water. Eventually, amid the dry hills, you see the first alien tower of a palm tree, and you know the desert is going to break soon.

Of course, I like the narrative arc on the drive back even better. Leaving Berkeley in the morning, you hit the desert in its element – bright and dry – without being too hot. That comes later, amid the rows and rows of fruit and nut trees, which turns into the mountains again, and into the land on the side of the mountains, now dominated by lower bushy produce crops and acres of flat grain land. You pass a sign for Lynn County, the Grass Seed Capital of the US. Finally, well into dusk, you hit the Washington border, and the first rain you’ve seen on the entire trip starts falling right on cue. Then you meet some friends in your old college town for a quick sandwich and tomato soup at 11:30 PM, and everything is set right with the world, letting you arrive back home by an exhausted but satisfied 1:30 AM.

I like this drive for giving a city kid a slice of agriculture. I’ve written about the temporal scale of developments in agriculture, but the spatial scale is just as incredible. About 50% of land in the US is agricultural. Growing the calorie-dense organisms that end up on my plate, or fueling someone’s car, or exported onto someone else’s plate, or someone else’s feedbag, is the result of an extraordinary amount of work and effort.

I talked about the plants – there’s trees for fruit and nuts, vines, grain, corn, a million kinds of produce. I only assume this gets more impressive when you go south from San Francisco. (In recent memory, I’ve only visited as far south as Palo Alto, and was shocked to discover a lemon tree. With lemons on it! In December! Who knew? Probably a lot of you.)

There’s also animals – aside from a half dozen alpacas and a few dozen horses, you spot many sheep and many, many cows from the highway. The cattle ranches were quite pretty and spacious – I wonder if this is luck, or if there’s some kind of effort to put the most attractive ranches close to the highway. Apparently there are actual feedlots along I-5 if you keep going south. I certainly didn’t notice any happy chicken farms along the way.

And then there are the bees.

I.

Bees are humanity’s most numerous domesticated animal. You don’t see them, per se, since they are, well, bees. What you can see are the hives – stacks of white boxes like lost dresser drawers congregating in fields. Each box contains the life’s work of a colony of about 19,200 bees.

800px-osman_bey_ve_arc4b1larc4b1

I forgot to start taking photos until it was already dark out, so here are some Wikimedia photos instead. If you want me to take more photos, feel free to ask for my paypal to fund me making the drive again. 😛 | Photo by Fahih Sahiner, CC BY-SA 4.0

The boxes look like this. The bees look like this.

Bees are enormously complicated and fascinating insects. They live in the densely packed hives described above, receiving chemical instructions by one breeding queen, and eusocially supporting her eggs that become the next generation of the hive. In the morning, individual bees leave the hive, fly around, and search for pollen sources, which they shove into pouches on their legs. Returning, if they’ve located a juicy pollen source, they describe it to other bees using an intricate physical code known as the waggle dance.

waggle_diagram

Waggle dance patterns performed by the worker bees. | North Carolina State Extension publications.

What images of this don’t clearly show is that in normal circumstances, this is done inside the hive, under complete darkness, surrounded by other bees who follow it with their antennae.

The gathered pollen is used to sustain the existing bees, and, of course, create honey – the sugar-rich substance that feeds the young bee larvae and the hive through winter. Each “drawer” of the modern Langstroth beehive – seen above – contains ten wooden frames, each filled in by the bees with a wax comb dripping with honey. At harvesting time, each frame is removed from the hive, the carefully placed wax caps covering each honey-filled comb are broken off, and the honey is extracted via centrifuge. (More on the harvesting practice.)

Each beehive makes about 25 pounds of harvestable honey in a season, and each pound of honey represents 55,000 miles flown by bees. Given the immense amount of animal labor put into this food, I want to investigate the claim that purchasing honey is a good thing from an animal welfare perspective.

I’m not about to say that people who care about animal welfare should be fine eating honey because bees don’t have moral worth, because I suspect that’s not true. I suspect that bees can and do suffer, and at the very least, that we should consider that they might. The capacity to suffer is evolutionary – it’s an incentive to flee from danger, learn from mistakes, and keep yourself safe when damaged. Bees have a large capacity to learn, remember, and exhibit altered behavior when distressed.

Like other social insects, however, bees also do a few things that contraindicate suffering in most senses, like voluntarily stinging invaders in a way that tears out some internal organs and leaves them at high risk of death. In addition, insects possibly don’t feel pain at the site of an injury (though I’m not sure how well studied this is over all insects) (more details). They may feel some kind of negative affect distinct from typical human pain. In any case, it seems like bee welfare is possibly important, and since there are 344,000,000,000,000 of them under our direct care, I’m inclined to err on the side of “being nice to them” lest we ignore an ongoing moral catastrophe just because we didn’t think we had incontrovertible proof at the time.

This is harder than it sounds, because of the almonds.

II.

The beehives I saw on on I-5 don’t live there full-time. They’re there because of migratory beekeepers, who load hives into trucks and drive them all over the country to different fields of different crops. As we were all told in 3rd grade, bees are important pollinators, and while the fields of old were pollinated with a mix of wild insects and individually-managed hives, like other animal agriculture, the bees of today are managed on an industrial scale.

(We passed at least one truck that was mostly covered with a tarp, but had distinctive white boxes visible in the corners. I’m pretty sure that truck was full of bees.)

60-75% of the US’s commercial hives congregate around Valentine’s Day in the middle of California to pollinate almonds. When we say bees are important pollinators, one instance of this is that almonds are entirely dependent on bees – every single almond is the result of an almond tree flower pollinated by a bee. California grows 82% of the world’s almonds.

According to this Cornell University report, honeybees in the US provide:

  • 100% of almond pollination.
  • 90% of apple, avocado, blueberry, cranberry, asparagus, broccoli, carrot, cauliflower, onion, vegetable seed, legume seed, rapeseed, and sunflower pollination.
  • 80%+ of  cherry, kiwifruit, macadamia nut, celery, and cucumber pollination
  • 70%+ of grapefruit, cantaloupe, and honeydew pollination.
  • 60%+ of pear, plum, apricot, watermelon, and alfalfa seed and hay (a major food source for cattle) pollination.
  • 40%+ of tangerine, nectarine, and peach pollination.
  • 5-40% of pollination for quite a few other crops.

Our agricultural system, and by extension, the food you eat is, in huge part, powered by those 344 trillion bees. Much of this bee power is provided by migratory beekeepers. In total, beekeepers in the US make about 30% of their money from honey, and 70% from renting out their bees for pollination.

Sidenote: All of the honey bees kept in the US are one species. (There are also 3000 wild bee species, as well as wild honey bees.) So we’re putting all of our faith in them. If you haven’t been living under a rock for the last decade, you may have heard of colony collapse disorder, which I’d wager is the kind of thing that becomes both more likely and more catastrophic when your system is built on an overburdened monoculture.

III.

Does this mean you actively should eat honey? I really don’t know enough about economics to say that or not. If you’re averse to using animal products, I don’t believe you’re obligated to eat honey – there are many delicious products that do what honey does, from plain sugar to maple syrup to agave to vegan honey.

But if you don’t eat honey and tell other people not to eat honey, I imagine you’re doing that because of a belief that this will lead to fewer bees being brought into existence and used by humans. And if you have this belief that it’s better to have fewer bees used by humans, I’m very curious what you think they’ll be replaced with.

What if you want to reduce the amount of suffering comprised by honeybees in your diet, or in agriculture in general?

One thing people have thought of is encouraging pollination by wild bees and other insects. When thinking about the volume of honeybees you’d need to replace, though, you start to encounter real ethical questions about the welfare of those wild bees. Living in the wild as an insect is plausibly pretty nasty. (I don’t have the evidence either way on whether honey bees or wild bees have better lives – but that if you care about honey bees anyway, it bears considering that this would require humans replacing the huge number of honey bees with other life forms, and that the fact that they’d be living on their own in hedges next to a field, rather than in a wooden hive, doesn’t automatically mean they’ll be happier.)

In addition, scaling up wild pollinators to the scale that would be needed by commercial agriculture would be difficult. Possible, but a very hard problem.

You could eat crops that aren’t mostly pollinated by honeybees. This page lists some – a lot of vegetables make the list. Grains, cereals, and grasses also tend be wind-pollinated.

Beekeeping seems like it might be better than increasing the number of wild pollinators, but migratory beekeeping as a practice reduces bee lifespans, and increases stress markers and parasites compared to stationary hives. Reducing the amount of travel modern hives do might be helpful. Maybe we could just stop growing almonds?

(Although that still leaves us with the problem of apple, asparagus, avocado, blueberry, broccoli, carrot, cauliflower, cranberry, carrot, onions, rapeseed, sunflowers, vegetable seeds, legume seeds, rapeseed, sunflowers…)

It also seems completely possible to raise beehives that are only used for pollination and not honey. This still requires animal labor and more individual bees, but the bees would have less stressful lives.

Or look into robot pollinators.

None of these ideas feel satisfactory, though. I feel like we’ve made our nest of bees and now we have to sleep in it. Any ideas?

beehives_on_the_road

Truck full of beehives. | Photo by Wendy Seltzer. CC BY 2.0.

(Note: I’m aware that this piece is very US-centric. I’m not sure what the bee situation is other countries is like.)