Diets Of Our Closest Living Relatives

Wikipedia says chimpanzees are a type of great ape (Hominidae), "the closest living relatives to humans," and are fruit-loving omnivores (they hunt lower order primates).

They say bonobos are a type of great ape, along with chimpanzees are "the closest extant [living] relatives to humans," and are primarily frugivores (fruit-eating) but "supplement their diet with leaves and hunt for meat from lower order primates."

They say gorillas are a type of great ape, "the next closest living relatives to humans after the two chimpanzee species," and that they are primarily herbivores that supplement their diet with insects.

They say orangutans are a type of great ape, next in line genetically after the gorilla, possibly "the world's most intelligent animal other than humans," and are fruit-loving foragers, consuming "leaves, shoots, seeds and bark ... insects, honey and bird eggs."

So, our closest relatives, the chimpanzees and bonobos, eat meat (and fish as I read). But the next genetically removed, gorillas and orangutans, it seems, couldn't be bothered to hunt, or so it was thought.

Since studying apes' diets in the wild is difficult, this study:
Interactions Between Zoo-Housed Great Apes And Local Wildlife, Am J Prim, 2009

... turned to zoos, asking caretakers about apes' interactions with local wildlife. Chimps and bonobos didn't surprise the researchers:

"Chimpanzees and bonobos demonstrated the most aggressive behavior toward wildlife. ... Captive gorillas and orangutans were reported to be much less likely to chase, catch and kill wildlife than chimpanzees and bonobos."

The gorillas did surprise them:

"Unlike wild gorillas, captive gorillas were reported to kill (and in one case, eat) local wildlife." (A bird.)

Orangutans were also observed hunting small game successfully.
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While reading about apes and their diets, I came across this paper:
Bonobo Nutrition - Relation of Captive Diet to Wild Diet

I liked the glimpse of what bonobos are fed in zoos.

Their basic diet was a mix of carrots, tubers, celery, apples, oranges, grapes, lettuce, bananas, raisins, green beans, and other fruits and vegetables. Most items were raw, whole or cut up. Nuts, seeds, flaked grains, cooked beans, and peanuts supplemented the basics. Meat, milk, cheese, and eggs were fed occasionally. Some zoos added dog food, monkey food, and Ensure.

Many gave vitamins, e.g. Super Acerola (500 mg natural vitamin C) and Mazuri Vita-Zu brand vitamins. "Cincinnati supplemented the bonobo diet with children’s chewable multi-vitamins."

Some of the apes had weight problems and diabetes, so their food was rationed, e.g. 1 apple instead of 2, a quarter of a sweet potato instead of a whole, and 8 celery sticks instead of 6.

Bonobos at:

• Berlin Zoo had "tea in the afternoon."
  
• Leipzig Zoo had "herbal tea at 8.00 and 13.00."
  
• Twycross Zoo had "skimmed milk with Ovaltine - approx. 2 pints per adult"
  
• Milwaukee County Zoo had "raisins, 10 per animal." (Cruel.)

________Photos: Top left: chimpanzee and bonobo (from Wikipedia). Bottom right: gorilla and orangutan (from duiops.net).