What happens to cows in the US?

(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

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.


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.

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.

Photo by Waugsberg, CC BY-SA 3.0.

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 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.


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.


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?

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.)

So You’re Not Ready To Go Vegetarian

[Content warning: Moralizing about what food you should eat, descriptions of bad things happening to animals, eating bugs. Also, lots of people can’t go vegetarian or significantly alter their diet at all due to health, cost, time, sensory issues, strong preferences, lack of options, inability to pick your own diet, etc. Most of the ‘alternatives’ posed here take money, time, or majorly changing your habits. If reading this post is likely to make you feel guilty or bad in an unproductive way, feel free to skip it.]

This is a rather utilitarian list of approaches to improving the lives of animals even if you still eat meat. I’ll start with some general strategies, ranked roughly in order from “least  to most weird”. See what works with your diet, resources, and preferences.

 Basic ideas:

  • Eat less meat in general.
  • Eat less chicken, eggs, beef, and farmed fish.
  • For other animal products, eat Animal Welfare Approved, Certified Humane, or 100% Grass-Fed meat, or buy from a source where you know how the animals are treated.
  • Eat species that suffer less, either in farms or at all.
  • Pay other people to go vegan for you.
  • Support animal welfare by donating money effectively.

I suspect that some people will object to the notion that it’s ever alright to kill or use an animal, and that encouraging people to do this in a “less bad” way is just making compromises with the devil. (As opposed to veganism, which is merely selling your soul to Seitan.) If you’re one of these people, you’re probably already a vegan and this essay isn’t for you.

Not that I entirely disagree- many more people should be vegetarian. That’s not the point, though. Many people are Vegetarian Sympathizers, as I once was. As a young person, for instance, I knew that I had moral issues with the idea of eating animals- that a cow’s brain wasn’t very different from a cat’s, which also wasn’t very different from a human’s. I also knew that meat had unfortunate impacts on the environment and that global warming was a serious problem. But my developmental environment had lots of meat. And also, I had a very strong objection- cheeseburgers.

Pictured: The Seattle restaurant that was the source of my conflict. The mind is willing, but the flesh is weak. | By Jmabel (CC BY-SA)

This wasn’t a rational objection. But we’re not rational creatures, and the Cheeseburger Objection was the actual thing standing in between me and vegetarianism. And if I’m going to eat cheeseburgers anyways, why not eat steak, chicken, fish, etc.?

Honestly, the Cheeseburger Objection is a pretty good one. One cow makes a lot of cheeseburgers. One cheeseburger might make you very happy. Acknowledging that isn’t a reason to stop caring about animal welfare entirely. And Cheeseburger Objectionists can still make extremely meaningful contributions to animal welfare without depriving themselves of that cheesey goodness.

1. Only go vegetarian sometimes.

Meatless Mondays are a thing- don’t eat meat just one day a week. That’s 1/7 fewer animals you’re eating, and gaining valuable practice in cooking and eating vegetarian. If that’s too easy, up it to two days a week. Repeat.

Some other strategies that have worked for people: eat vegan before 5 o’clock (IE, meals before dinner), only eat meat outside the house, only eat meat inside the house.

Or, if you’re inclined towards vegetarianism- except for cheeseburgers- (or orange chicken, shrimp, your uncle’s venison, baseball stadium hotdogs, etc.-) consider just being a Cheeseburger Vegetarian. I think there’s this tendency to think that if you’re not doing something 100% all the way and identify as that, any tendency you have towards it doesn’t count at all. But that’s completely untrue. Given that we live in a world where most people do eat meat, conspicuously eating less meat both saves animals, and is a talking point that puts vegetarianism on people’s radars.

(Of course, if you’re being a Cheeseburger Vegetarian and hoping to talk to other people about it, people might take you less seriously. This might be a problem. You could either keep your cheeseburger habit private and secretive, hoarding McDonald’s in the dark like the world’s most gluttonous dragon – or you could acknowledge that if someone’s going think that plant-based diets are a joke and not important, they can already find whatever reason they want to do that.)

If you don’t know how to cook food or eat meals without meat, maybe the problem is educational. Look for recipes that contain tofu, beans, lentils, TVP, or vegetables. If you only know one kind of cuisine, broaden your horizons- Indian, Ethiopian, Mexican, Chinese, etcetera, all have lots of opportunities for low meat dishes.

We live in a golden age of easily available recipes. PETA, Vegetarian Times, and Leanne Brown’s free cookbooks are a few good resources. Google it. Also, if you want to make a favorite Food X vegan or vegetarian, look up “Vegan Food X” and you will instantly get 4,000 hits including step-by-step photographs and people’s life stories as told through salad dressing recipes. The internet is a magical place.

2. Eat humanely sourced meat.

This is way harder than it sounds. The good news is that meat is given labels which reflect how it was raised. The bad news is that some of these labels are regulated, and some aren’t, and it’s difficult to determine which labels actually correspond to good living environments and which are symbolic or easily falsified.

Look for the following words on packages:

Certified Organic animals may still be subject to a variety of inhumane conditions. The label means that hormones, antibiotics, and some other treatments are not allowed, and that the animal must be allowed to “exhibit natural behaviors.” I suspect that organic animals are somewhat harder to mistreat, because farmers are incentivized to raise animals in low-disease environments, so organic may be better than conventional if those are your only two options. *

Animal Welfare Approved is an independently-verified certification that has very high welfare standards, including for slaughter. Certified Humane is a less strong but similar certification. There are probably other good ones- look for what they require and how they’ve verified.

Hoofed animals: Look for 100% Grass-Fed, a legally-defined term in which all animals must be raised entirely on pasture (grass, etc) and not fed harvested grain. It seems much harder to mistreat a cow raised this way, since it can’t be confined. This is different from grass-finished, pastured, or normal grass-fed, since all cows eat some grass before they arrive at feedlots.

3. Be careful with chicken.

Chickens are extremely common and live extremely bad lives in factory farms, probably moreso than any other animal.

Cage-free or free-range eggs are better than alternatives, but I don’t think they’re humane. A cage-free chicken may have a somewhat better and more natural life than a non-caged chicken, though they’re newly at risk of fighting with other chickens, which caged chickens aren’t. They may still be subject to having their beaks cut off, slaughter of male chicks (half of all egg-laying chickens are killed shortly after hatching), bird flu, crowded environments, being raised in darkness, starvation-based forced molting, etc.

A couple examples:

  • Free-range – the amount of time or space required for “outdoor access” isn’t legally defined, and varies from facility to facility.
  • A cage-free chicken is still raised in barns or warehouses. They may have no outdoor access, or have their beaks cut or burned off without anesthesia.
  • Organic eggs still aren’t treated with antibiotics but can still be raised in factory farms.
  • More info on labels.
Putting a picture of happy chickens here seemed disingenuous, so here’s some eggs, I guess. | The Home Front In Britain, 1935-1945.

Any given egg source may well not do some or all of these- for instance, I’ve heard that there are some egg producers that don’t slaughter male chicks, and the cost of raising them is passed to the consumer as a higher price. The key here is to do your research. If you buy based on label X or Y without further investigation, even at a “nice” natural foods store or co-op, your chicken will probably have been raised in painful, inhumane conditions.

I think your best chance at getting humanely raised chickens or eggs is to buy from a home farmer or very small permaculture farm, ideally where you can see the chickens. These are likely to be significantly more expensive than other options. Farms may still slaughter male chicks.

4. Eat species that suffer less.

Quantification of animal suffering is a new field, and practices for calculating it are general estimates. That said, its numbers come from easily understandable ideas- that it’s worse to be a factory-farmed chicken than a feedlot cow, for instance. Some other ideas include that being killed is painful, so an animal that produces more food over a long period means less suffering per food unit (assuming said animal’s day-to-day existence isn’t terrible.) Also, that having a more complex brain probably means you can suffer more. It’s not an exact science, but it’s what we’ve got.

Brian Tomasik, who has studied animal suffering extensively, suggests using this metric that by eliminating chicken, chicken products, and farmed fish from your diet, you reduce the suffering you inflict on animals by an enormous amount.

Clams and mussels have very simple nervous systems and probably do not feel much pain, while full of nutrients comparable to other animal foods. Ozymandias at Thing of Things suggests that eating bivalves and dairy, and otherwise being vegan, can be a good trade-off between health, enjoyment, and helping animals. Also, you still get to eat clam chowder (if it doesn’t have bacon.)

The jury is still out on whether insects experience suffering. On one hand, insects are pretty simple critters; on the other hand, to produce any significant amount of food, you need a lot of insects, so however much moral weight they do have gets multiplied by a lot. On the third hand, about a quintillion die every year, so your own contribution is pretty marginal. (That number is extrapolation- I suspect most insects live less than a year, so the number is probably higher.)

Chingrit thot by Takeaway (CC BY-SA)

What is known is that insects are nutritious and environmentally friendly. Sourcing insects is difficult and pricey, so try raising your own.

Exotic meats. I suspect that exotic meats (deer/venison, buffalo, ostrich, etc.) are more likely to be raised in more ethical environments, because as species they’re less domesticated, and therefore harder to mistreat as in a factory farm. However, I have no evidence for this.

5. Eat environmentally sound meat.

Most of this list comes from a moral argument, but the negative environmental impacts of standard meat is so well-established that it’s worth discussing. 30% of the world’s non-frozen dry land is currently devoted to feeding or raising animals, and 18% of human-produced greenhouse gases came from agriculture. Lamb and beef have disproportionately high greenhouse gas emissions. You’ll note that chicken is rather low on this ranking, but as in the above section, there are other reasons to avoid it.

“Don’t non-animal-product foods also have carbon emissions?” Not that much.

Source and more info.

Fish is extremely nutritious, but many species are overfished. Eat conscientiously to avoid making the problem worse- the Monterey Bay Aquarium Seafood Watch has detailed recommendations for the consumer based on your location, sorted into handy “okay to eat” and “avoid this” categories. Bycatch ratios are another thing to beware: shrimp fisheries are the worst, trawling up an average 6 times more non-shrimp than shrimp.

6. Convince someone else to go vegan.

A review (again by Tomasik) of organizations that run ads promoting vegetarianism suggest that the cost of converting a someone to be vegan for a year is, conservatively, about $100. Do you have the money to spare, and think there should be more vegans, but eating meat is worth more than a hundred dollars to you?

Utilitarianism: it works.

cool skeleton
Utilitarianism: It’s this cool. And the ends justify the memes.

This approach won’t work forever, of course – if everybody decided that they individually would eat meat but convince others not to, the cost of getting anyone to go vegan would skyrocket. But not everybody is, and for the time, it’s still low-hanging fruit.

7. Donate to effective charities.

Can we do even better? The average vegetarian saves ~25 land animals per year (and perhaps 371-582 animals per year including fish and shellfish) according to the blog Counting Animals.

The Effective Altruism movement, which is near and dear to my heart, has produced several lovely projects, including Animal Charity Evaluators– a highly evidence-based group that researches which animal welfare organizations have the most bang for your buck. (Sort of the Givewell of the greater biosphere.) An $100 donation to any of their top three charities is estimated to indirectly save or spare the lives of 7,597 animals. (Via outreach, undercover video filming, corporate outreach, and more.)


A final note: People sometimes get annoyed at vegetarians or vegans because they think they’re being smug or morally uppity. This always seemed to me like a strange criticism – the problem is that they’re doing something good? – but if you think it has merit, imagine how smug you can feel in the knowledge that every year, you donate $100 to a certain charity, and that has the same effects as going vegetarian for thirteen years, every year.**

Updated 4/14/2017.

Further reading:

* Michael Pollen says in his book The Omnivore’s Dilemna that it’s difficult to get Organic certification, which has many requirements and regulatory steps, so some small and comparatively extremely humane farms may not (despite meeting many or all criteria for the certificate.)

**Note that you’re not allowed to use this to smugly dismiss vegetarianism unless you have actually made a substantial donation to ACE charities. If you don’t, and proceed to use the fact that that someone could make such a donation to be a dick to vegans, you’re doing negative good and the Utilitarianism Skeleton will get you.



What’s the most common animal species?

I tried to answer this question by doing some reading. Why should we care?

  • Most people don’t have a good sense of the scope and scale of biodiversity and common species on the planet. Whatever you think are the most common inhabitants of earth, you’re probably wrong.
  • When scientists think of “successful” organisms, they tend to think of ones with great diversity: beetles, for instance, or in terms of environments, rainforests. Looking at sheer numbers of individual species is another way of doing this.
  • “Okay,” you say, “Why animals, and not plants or bacteria? Those are way more common.” I study bacteriophage. I know. Two reasons: Animals have brains, which is one reason to focus on them- don’t you want to know who’s doing the majority of the world’s thinking? Secondly, it’s harder to find data on non-animals, but stay tuned.
  • Similarly, if you’re concerned about wild animal suffering, this may give you a sense of where best to focus your concern.

Mammals don’t come anywhere near the top, but sure, they’re furry and warm and cute and also you’re one, so let’s begin here. Humans aren’t actually a bad call as far as larger organisms- there are 7.5 billion (7,500,000,000) of us crawling around the planet, handily beating out other close competitors.

Rule 1: If you want to make an organism numerous, association with humans is a good start.

Large wild mammals are not especially common. Cows (1.4 billion) have the largest non-human large mammal population, and sheep, pigs, and goats (~1 billion each) beat out all other competitors. The curious will be interested to know that there are 50% more cats globally than dogs (600,000,000 vs 400,000,000).

What about birds? As of 1997, between 200 and 400 billion (brought to us by the excellently titled paper, How Many Birds Are There?) The most numerous wild bird is the red-billed quelea, which terrorizes African farmers in enormous flocks (1.5 billion). (The Smithsonian flagrantly claims it’s the house sparrow, but the population of those is maybe half a billion and dropping.) Again, association with human comes in- the most common bird is the chicken, at 19 billion (19,000,000,000) or 2.5 chickens per human.

Hundreds of roosters standing in a field
“Capons in Hainan” by Anna Frodesiak / CC0 1.0

So chickens are looking good so far. What about mice or rats? They’re tiny, reproduce voraciously, and also follow humans. Unfortunately, I couldn’t find good estimates on global mouse populations. Maybe there’s ten mice per human? Maybe there’s 75 billion mice. Sure. Fortunately, it doesn’t matter. Remember the grand rule of biomes:

Rule 2: Whatever’s happening in the ocean is much bigger and much wackier than anything on land.

Longtoothed bristlemouth
NOAA Photo Library / CC BY 2.0

You’ve probably never heard of the bristlemouth, genus Cyclothone, a three-inch-long deep-ocean fish with a big mouth and weird teeth. As it happens, most of the planet’s surface is deep ocean. Unspecified “icthyologists” found by the New York Times speculate a population in the hundreds of trillions (> 200,000,000,000,000).

Their sheer population has only recently come to light- they’re found many meters deep into the water column and don’t surface at night, and the extent of their dominion has only recently been discovered via trawling with fine nets and the dawn of deep-sea exploration. If these “ichthyologists” can be believed, the bristlemouth is probably the most common vertebrate on earth.

Maybe you’re confused as to how there could be so many bristlemouths, since they’re relatively large compared to, say, insects. I’m not actually convinced that the trillions number is correct, but nonetheless, consider: The oceans represent 75% of the planet’s surface, and while land animals are more or less limited to a flat surface, ocean animals can “stack” in three dimensions.

Finally, a fun fact: If a bristlemouth brain weighs as much as a goldfish brain, then:

7,500,000,000 human brains * 1,350 grams/human brain = 10,000,000,000 kg

200,000,000,000,000 bristlemouth brains * 0.097 grams/bristlemouth brain = 19,400,000,000 kg

Mass of human brains ≈ mass of bristlemouth brains

Draw your own conclusions.

Rule 3: Ant biologists need to get it together.

Ants feeding on a honey droplet
“Meat eater ants feeding on honey” by flagstaffotos / CC BY-NC

All the world’s ants are popularly said to weigh the same amount as all the world’s human beings. It takes 16 million ants to outweigh a human, and since your garden-variety ant colony has about 4,000 ants, that would be 40,000 ant colonies per person.

This sounds ridiculous, and a University of Sussex professor suggests that it is– that ants may have outweighed humans earlier in our existence, but we’ve spread too far too quickly for them to catch up. This article posits 100,000,000,000,000 (1×1014) ants.

But wait. A different article from BBC suggests 1,000,000,000,000,000,000,000,000 (1×1024).

What’s going on here? To our instinctive brains, both of those guesses occupy a similar conceptual space as “really large numbers”, but they’re not close. They’re ten orders of magnitude apart. One of these numbers is ten billion times larger than the other. There’s one quantity of ants, or there’s ten billion times that number of ants. What?!

I have no idea. Worse yet, they’re both from the same source. The BBC can’t be a reliable news source if they don’t have a standard journalistic value for “total number of ants” that’s rough to within oh, say, five orders of magnitude.

Fortunately, we can perform a sanity check. The earth has 1.5×1014 square meters of dry land.

1×1024 global ants / 1.5×1014 square meters = ~7,000,000,000 ants per square meter

Given that we’re not swimming in ants at every single moment, we can knock off a few zeroes and come down to 1×1019 (10,000,000,000,000,000,000 or ten billion billion ants, at 70 ants per square meter, which seems more reasonable.)

Even if the most common ant species is just 1% of all ants, where ants ranks depends drastically on which value the right value is. Bristlemouths might outnumber them, or they might not. Dear ant researchers: work on this, but at the least, stop telling people there are 1×1024 ants. That’s too many ants.

(While researching this, I also learned about the long and short scales– everyone uses the same “million”, but my “trillion” may not be the same as your “trillion”. While normally I try to avoid being prescriptivist about language, this is a terrible use of words and everybody should either use lots of zeroes or scientific notation from here on out. Ugh. Anyways.)

Antarctic krill
Antarctic krill by Uwe kils / CC BY-NC

The antarctic krill is the foundation of the antarctic ecosystem. It feeds whales, seals, squids, fish, and everything else. 500 million tons of it exist, and Wikipedia claims it’s probably the most abundant species on the planet. Using Wikipedia’s mass value of up to 2 grams (say, 1.5 grams on average), that’s 3×1014 (300,000,000,000,000) krill.

Rule 4: Maybe we just don’t know what’s going on.

Let’s talk about uncertainty. There are a couple other candidates. They may easily hold the title, but I don’t know because nobody has done the research. There are certainly plausible reasons to suspect any of them of holding the title, and we can use Fermi calculations for the sake of a guess, but I don’t expect these to be very accurate.

Most of the guesses above did come with specific numbers, but aren’t necessarily completely trustworthy. Articles written about ants, antarctic krill, nematodes, and copepods have all variously claimed to be the most common animal. It seems like this could happen because of the availability bias– if you’re a krill biologist, and someone asks you what the most common animal is, and you know that there are a whole lot of krill, you’re probably going to say krill.

Narrowing down a common species is also more difficult- I can attest (from work with tiny snails) that doing field identification via microscope is the worst. So presumably, most studies don’t do it, and focus on the broader picture.

Alternatively, invertebrate researchers have field-wide conspiracies in order to get more grant money. Invertebrate researchers are welcome to deny this in the comments.


Tiny free-swimming ocean crustaceans, at the root of many food chains.

By Uwe Kils / CC BY-NC

Some scientists say they form the largest animal biomass on earth.


Copepods almost certainly contribute far more to the secondary productivity of the world’s oceans, and to the global ocean carbon sink than krill, and perhaps more than all other groups of organisms together. – Wikipedia

Also, bristlemouths eat them. Oceanic food chains don’t always work the same way land food chain pyramids do- there’s not necessarily more biomass at the base of the chain than at the top– but as far as I know, it’s strong evidence for them having more biomass.

Frustratingly, as with the nematodes, nobody seems to know what the most common copepod is.

My probable candidate:

  • A small cosmopolitan mid-ocean-level copepod.

Copepod expert Geoff Boxshall on Plankton Safari estimates 1.3×1021 (1,300,000,000,000,000,000,000) copepods. If the most common species represents 1% of all copepods, that’s 1.3×1019 of a common copepod species out there.

But I think we can do better.One study found an average 20 zooplankton per cubic meter in the Atlantic ocean, with occasional high spikes and huge seasonal variation. If we assume that such a number is constant over all the oceans and throughout the euphotic zone (the top layer of the ocean that receives sunlight and supports photosynthesis), that adds up to at least 5.78×1017 plankton. Since we know copepods are quite common, let’s say that 50% of the zooplankton is copepods, and that the most common species represents 1% of all copepods. That’s:

5.78×1017 zooplankton worldwide x (50% copepods) x (1% of the most common species) = 2.89×1015 of the most common copepod.

By Lennart Lennuk / CC BY-SA


They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as mountains, deserts and oceanic trenches. – Wikipedia

Everyone (read: all scientists who have expressed an opinion on the matter) seems to think that nematodes are incredibly numerous. That said, Nematoda is a very broad umbrella- sort of like saying that there aren’t very many Chordates (the phylum that contains all vertebrates plus a handful of squishy sea creatures.) Bristlemouths, meanwhile, are narrowed down to a single genus of only a dozen species.

My guesses for a candidate Most Common Nematode are:

  • A small, free-living, deep ocean floor or mid-ocean-level species
  • A small parasitic nematode that inhabits cattle or bristlemouth guts.

(Why these two? My educated guess is that smaller animals tend to be more common, and that the smallest species are routinely parasites. Other small species tend to be among the more numerous free-living animals- think mice and Palegibacter ubique.)

My extrapolations (more details on those numbers) from a 2006 study of benthic microfauna – very small animals living on the ocean floor at various depths – suggest that there are maybe 9.03×1019 such critters in Earth’s oceans. These include nematodes, benthic copepods, and other species. As with copepods, let’s guess that half of these are nematodes, and that 0.1% of nematodes are in the most prolific species.

9.03×1019 microfauna on the ocean floor x (50% nematodes) x (0.1% of nematodes in the most common species) = 4.52×1016 of a common nematode species.

This aligns well with another, rougher back of the envelope calculation from a different source:

Roughly 2000 nematodes / square meter * (5.1×1014 meters on the ocean floor) * (1% of nematodes in most common species) = 1.02×1016 (1,020,000,000,000,000) of a common nematode species.

Conclusion: It’s a nematode world.

Bunch of nematode worms
By Matthieu Deute / CC BY-SA

[Updated as of 4/14/2017.]