The group marched in silence until a scream broke everyone into a sprint. The hunt was on.
Another noise I didn’t recognize joined the chimpanzees’ pants and shrieks. The alarms from red-colobus monkeys only fed the frenzy. On all sides, adult males, females, juveniles ascended tree trunks. I looked up to see clambering bodies cornering their victims at the top of the canopy. Suddenly, a chimp climbed down, a fuzzy body dangling in his mouth. By the end of the hunt, there would be four dead monkeys.
Just another day researching the Ngogo chimpanzees of Uganda. I had never seen chimpanzees hunt before, but just last week I saw two.
Just after the kill, Jackson charges with prey in Hand. Morton holding his own monkey moves to get out of the way. A female descends the tree to follow, hoping to get some meat of her own. (Sorry for poor quality! Uploading from rainforest has its limits)
A hunt earlier last week: Brownface (a 52 year old male) consumes a black and white colobus infant.
What meat do chimps eat?
Anything they can get their hands on. Small mammals are preferred prey, and often monkeys like the red colobus. For instance, the Fongoli chimpanzees are known to kill bush babies (another primate), sometimes by thrusting a stick into a tree cavity. You read that right, spears! Chimpanzees may also snatch up duiker, or forest deer. After killing another chimpanzee, they may even cannibalize. Regardless, the red colobus do seem to be preferred prey as on this day.
A red colobus monkey. Eating infants and juveniles is much more common. Even for the biggest chimpanzee, an adult male red colobus is intimidating and dangerous. Note : chimps are apes, not monkeys. Monkey = tail. Ape = no tail. Photo by David Edric.
When do chimpanzees hunt?
Chimpanzees don’t hunt when food is scarce, just the opposite. The Ngogo chimpanzees hunt more when they can get enough energy elsewhere. It makes sense. Hunting is energetically expensive and risky; they might not find prey, or might not manage to catch anything.
Are chimpanzees effective predators?
Yes, some estimate the chimpanzee hunting success rate to be around 60%. Here however, the Ngogo chimpanzees enjoy an especially high success rate of over 80%. Compare this to studies of carnivores: lions at 26%, cheetahs at 30%. Why so good? Maybe this is because Ngogo simply has more chimpanzees, and the size of the hunting party correlates to hunting success. Overall, it might also help that chimpanzees do not need to hunt everyday or even often. They are primarily frugivorous as ripe-fruit specialists.
In fact, the Ngogo chimpanzees are such good hunters, they’ve practically driven red colobus to extinction in their territory. From 1995-2000, researchers observed 317 kills in this single community. They estimated that ≈ 3 - 4% of the red colobus population succumbs to chimpanzee predation each year. As a result, there isn’t nearly so much red colobus hunting as there used to be, and maybe the chimpanzees are switching to add other animals to their menu.
Declining red colobus population density from Watts & Amsler (2013) : Chimpanzee-red colobus encounter rates show a red colobus population decline associated with predation by chimpanzees at Ngogo
Do females hunt?
Yes again. Female chimps do hunt and eat meat. In fact, those who get more meat also have more kids.
Why do chimpanzees hunt?
Researchers debate this a lot. Some have proposed a meat-for-sex hypothesis. At one site, male chimpanzees mate females frequently if they have shared meat with them. However, this was only over an extended period, and other studies have shown no relationship between sharing and sex. Maybe meat is just nutritious. Chimpanzees appear to get especially excited when there is meat around. Some researchers think it may have important micronutrients, like vitamins, which could explain why meat isn’t an essential part of the diet, but is still highly valued.
The micronutrient value of meat also lends itself to the meat scrap hypothesis. Hunts might not be energetically efficient, but hunting in groups might be encouraged if many participants can obtain just a bit of meat.
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