Why Do Chimpanzees Eat Meat?

Chimpanzees eat meat for two simple reasons: they can catch it and they like it. Chimpanzees are particularly likely to eat meat during the dry season, when shortages of the foods that normally make up the bulk of theirdiet cause them to lose weight. Although the meat may be a useful source of calories during the dry season, wild chimpanzees don’t need to include meat or any other animal-based food in their diet to fulfill their needs for protein or any of the amino acids. In fact, plants provide all of the nutrients that are known to be essential for a chimpanzee, except for vitamin D (which they get from the abundant sunshine in Africa) and vitamin B12 (which comes from bacteria).

Many people think that I am silly for asking where gorillas get their protein. They tell me that I should talk about chimpanzees instead. Often, they inform me that chimpanzees are far more similar to human beings than gorillas are, as if I couldn’t tell that just by looking. These people are missing my point: gorillas are the largest and most powerful living primate and yet are the closest to following what human beings would consider a vegan diet. Chimpanzees and human beings don’t need to eat meat to grow up big and strong because gorillas grow up to be far bigger and stronger without it. Lawyers may recognize this as an a fortiori argument.

If a male gorilla, whose digestive system is practically identical to a human being’s, can get enough protein from vegetables to grow to weigh more than 400 pounds and be ten times as strong as a man, why shouldn’t I expect that a relatively puny human Olympic weightlifter could also get enough protein from a plant-based diet? My intent is to ridicule the Four Food Groups dogma that I was taught in sixth grade.

Gorillas don’t hunt or fish, and they don’t keep cows or chickens. As a result, they don’t eat meat or fish, dairy products or eggs. The only animal-source food they eat is “the other, other white meat”: termites, slugs, and other creepy-crawlies. These foods would make an insignificant contribution to the gorillas’ protein intake, which is already high because protein accounts for a high percentage of the calories in leaves.

Bugs and slugs could be a useful source of vitamin B12, a micronutrient that is made by bacteria in their intestines. Vitamin B12 is also produced by bacteria in a primate’s gastrointestinal tract. However, the vitamin may be produced so far along in the intestinal tract that it isn’t absorbed efficiently. No plants make vitamin B12, but gorillas and chimpanzees can probably get enough vitamin B12 from the bacteria in the bugs they eat and in the dirt that clings to their food. Plus, apes are not meticulous about washing their hands, if you get my drift. If you are worried about getting enough vitamin B12, you don’t have to eat dirt or bugs. You can get it in a nice, clean tablet instead.

I don’t ask where chimpanzees get their protein because chimpanzees do eat some meat. Chimpanzees probably eat less meat than just about any human population other than Buddhist monks. Nevertheless, many people want to use chimpanzees’ meat consumption as an excuse for humans to eat meat.

The fact that chimpanzees’ meat consumption is largely seasonal goes far toward explaining why human beings have always eaten meat. Chimpanzees are most likely to eat meat during the time of year when they are losing weight because their usual foods are in relatively short supply. People think of meat as a source of protein, but it’s mainly a source of calories, especially from fat. Meat is also a good source of sodium, which is in relatively short supply in the chimpanzees’ fruit and vegetable diet.

The fact that chimpanzees eat the most meat during times of food shortages suggests that their food choices follow a pattern that biologists call optimal foraging theory. Animals try to get the most calories for the least effort and without getting hurt. Optimal foraging theory explains why chimpanzees eat meat but gorillas don’t, and why chimpanzees eat more meat during times of food shortage.

Chimpanzees are mainly fruit eaters, but they also eat a lot of vegetables. The problem with fruit is that it’s seasonal. Worse yet, a fruit tree represents a rich enough source of calories that animals will fight over it. When fruit is scarce, chimpanzees can use the skills they developed in fighting over the fruit to engage in predatory behavior. Also, chimpanzees are small enough and fast enough that they are reasonably good hunters.

Gorillas, on the other hand, mainly eat leaves. There are generally plenty of leaves to go around, and a leafy plant is generally so poor in calories that it’s not worth fighting to protect. To subsist on leaves, however, you have to eat an enormous volume of food. Since leaves are so low in calories, leaf-eaters have to be good at conserving their energy. That’s why gorillas have such a placid disposition. For a gorilla, hunting is simply not worth the effort. They are too big and slow to catch very much, and they’re large enough that they’d risk injury if they got too reckless.

Chimpanzees use twigs to fish for termites, and gorillas don’t. Some people think that this fact means that chimpanzees are smarter than gorillas. I don’t. If you are a juvenile gorilla or a pregnant or nursing female gorilla, you don’t need to mess around with a little bitty twig to get a few termites. All you have to do is wait for the silverback to knock over a rotting tree. Then all of you can eat as many termites as you’d like.

Some people have argued that the balance between animal and plant foods in a hunter-gatherer society’s diet represents the optimal balance for human nutrition. I think that’s idiotic. Hunter-gatherer peoples (or should I say, gatherer-hunter peoples) tend to follow optimal foraging theory just like any other opportunistic feeder. Their goal is to survive in the short term, not to avoid breast or prostate cancer in middle or old age. The main threat to their short-term survival is starvation.

Meat represents a concentrated source of calories. The fact that a relatively high percentage of these calories comes from protein is actually a disadvantage. Hunting peoples prefer the fattiest foods. People who end up having to subsist on extremely low-fat meat, such as rabbit, are prone to a problem called fat-hunger or rabbit starvation. This problem probably results from a diet that has too much protein and not enough carbohydrate or fat. On a low-carb diet and during starvation, the body has to make its sugar supply out of protein. Perhaps the body can make only so much sugar out of protein. As long as you are eating enough fat to meet most of your energy needs, your body can make enough sugar out of protein to feed your brain. If you were eating protein but not enough fat or carbs, you could end up in serious trouble. So you could end up in trouble from a diet that is too high in protein. In contrast, it is practically impossible to avoid getting enough protein, as long as you are eating enough unrefined plant foods to get enough calories.

Famine is not a significant cause of death in the United States. In fact, people in the United States are far more likely to die of the diseases of affluence, such as heart disease and cancers of the breast and prostate. Animal-based foods and fatty processed foods are the main contributing causes of the diseases of affluence. The ability to use animals for food may have helped human beings survive to the modern era, especially in the Arctic, but animal-based foods are a major cause of death and disability in the United States today. Think about that the next time you hear someone promoting a “Paleo” diet.

9 thoughts on “Why Do Chimpanzees Eat Meat?”

  1. You are definitely my tribe. Paula Deen should be on death row, along with The Today Show cast which promotes her animal, fatty foods even while criticizing her for taking money from the diabetes industry — while she gives people diabetes on purpose. Eat pigs and you look like a pig, aka Paula Deen and Al Roker.

  2. Unfortunately, Paula Deen has put herself on death row by giving herself diabetes. Diabetes is one of the major causes of death in the United States, and it increases a person's risk of dying of some of the other major causes of death, such as heart disease, cancer, and stroke. If she uses antidiabetes drugs to control her blood sugar tightly, her chance of dying could actually increase.

    Personally, I'm too soft-hearted to give anyone the death penalty for any reason, but I would certainly never give it for hypocrisy. If all the hypocrites were executed, who would be left to go to the funerals? 😉

  3. Yes, there are vegan bodybuilders and weight-lifters. See http://www.veganbodybuilders.com. They don't look puny to me.

    The Food and Nutrition Board of the National Academy of Sciences concluded that there is no reason to believe that resistance training increases dietary protein requirements for human adults.

    Olympic track star Carl Lewis, who had his best year of competition while eating a totally vegan diet, argues that most athletes succeed despite their diets, not because of them. The fact that many weight-lifters eat raw eggs and so on is irrelevant. If they get a boost from all that protein-loading, it's because the excess of high-quality protein is causing their liver to secrete abnormally large amounts of insulin-like growth factor 1, which is also one of the most powerful known promoters of cancer growth.

    I am fully aware that a gorilla-style diet would be impractical for human beings because it would take about 8 hours a day to eat enough leafy vegetables to get enough calories. The problem would be getting enough calories, not getting enough protein. If you read my Web site, you'll find that I argue that the normal diet for a human being is based heavily on unrefined starches. However, people who are trying to lose a lot of weight would benefit from "going ape" and eating a diet more like a gorilla's.

  4. I'm a vegan and an athelete and can testify to the adequate protien I get. Since switching to vegan I have made the same gains in the gym as when I eat meat, plus more plants means more variety of carbs which fuels me for any endurance activities. Weight lifters do need a little more protein than the average person. But what people fail to notice is that they also need more carories as a whole. You may look at a body builders diet and say "wow, he eats 250g of protein per day! that's crazy." but then if you look at body builder diets many eat more than 6000 calories a day. Eating 250g of protien for 2000 calories is a big feat, but have 6000 calories makes it much easier. so now having 250g protein/6000 calories is equivalent to only 83g protein for an average 2000 calorie diet. Many atheletes have the mind set of just eating protien and no calories, which is terrible.

    The only time people have protein defficiencies are when they are starved. The only possible diet I can think of that is inadequate would be a rice, sugar, butter/oil and alchohol deit. spinach has about 3g protien per 20 calories so if someone just ate nothing but spinach they would have 300g protein for just a 2000 calorie diet! now thats the power of leaves!

  5. Thanks for commenting! Many people were concerned that the British food rationing system during World War I would lead to protein deficiencies. In response, a prominent British nutrition scientist wrote a book explaining that if you take care of the calories, the protein takes care of itself! The real cases of pure protein deficiency are in the sort of situations you mentioned: people getting nothing but sugar intravenously or alcoholics. However, rice does provide enough protein for human nutrition, including enough of all of the essential amino acids. The beriberi that occurred in people who were eating practically nothing but unenriched white rice resulted from vitamin B1 deficiency, not protein deficiency.

  6. Thanks for an intriguing site, Laurie. I'm delighted that it is based on science and evidence. I trust that will safeguard its sliding into some of the unrelated "woo" pseudoscience that seems to infect many other vegan (among other) sites.

    Your points are well taken. If I have any quibble it is the emphasis on chimps as omnivores as though that aspect of their diet were a given. I wrote on that years ago, but I'm not aware that any of my sources have been disproven. As of that writing it had been established that, whereas SOME chimp tribes, including, unfortunately, the one Dr. Goodall studied, do hunt monkeys and eat them, not all tribes do so. Furthermore, the hunting of the monkeys seems to have little to do with nutritional needs and is somewhat similar to a human sport, with the males doing the hunting and establishing hierarchies thereby. The dead monkey is usually given intact to a female in estrus, rather like, as I say in my paper, giving a lady a posy when calling upon her. Why a female chimp would be receptive to such a morbid gift is puzzling, but recent discoveries of female chimps carrying constructions of sticks as dolls may provide a hint. The female will sometimes carry the dead monkey around for a long while before actually taking a bite. At an anthropology convention in Knoxville last year I learned that meat passes through the chimp digestive tract largely intact, suggesting it provides the animal with scant nutrition.

    My paper was titled "Of Men and Monkeys, Memes and Meat," and was online last time I checked; a search should turn it up. If not, I'll provide a link if requested.

  7. I do not consider chimpanzees to be omnivores. A biological omnivore is an animal that is adapted structurally and metabolically to a mixed diet of animal and plant foods. I consider chimpanzees to be herbivores, mainly frugivores. (Gorillas are mainly folivores, which explains a lot of the physical and behavioral differences between chimpanzees and gorillas.) However, chimpanzees are, to some degree opportunistic feeders.
    Chimpanzees occasionally do hunt, and they sometimes eat their kill. However, I have pointed out that meat makes an insignificant contribution to their total diet. They certainly do not need it to meet their protein requirements. Chimpanzees probably eat less animal-source food than do any human society–except for The Vegan Society, of course.
    I have heard reports that meat passes through a chimp largely undigested, but I am inclined to doubt their veracity. There's no reason to believe that chimpanzees would be unable to digest meat. In fact, this experiment suggests that they can: http://onlinelibrary.wiley.com/doi/10.1002/ajp.1350180105/abstract

Leave a Reply

Your email address will not be published. Required fields are marked *