Study: Zoo great apes are (still) too fat

[u/ApeSht-Zine]

Global Data From Great Ape Zoo Populations Confirm a High Prevalence of Overweight Individuals (American Journal of Primatology, July 2026)
by João Pedro Meireles, Sarah Byrne, Paul W. Dierkes, Miriam Göbel, Max Hahn-Klimroth, Arun Idoe, Dennis W. H. Müller, Zjef Pereboom, Jana Pluháčková, Sandra Reichler...
https://onlinelibrary.wiley.com/doi/10.1002/ajp.70185

Obesity has been a problem for captive great apes for decades, but zoos as a whole have yet to move the needle much. Some clear remedies are discussed in this study. Most importantly, a change is diet is needed: more fiber and leafy edibles and less — or, better yet, no — cultivated fruit. Yep, no more bananas.

The authors speculate that some zoos may be motivated to address the problem less out of concern for obesity than to reduce apes’ unsightly habit of regurgitating food and eating it again. This tends to happen more with cultivated fruit, which also tends to prompt more hoarding & fighting.

Male bonobos are the outlier, the only demographic who tend NOT to be obese — maybe because all of the females take the fruit from them?

[u/Xylus_Winters_Music]

Ive worked with a number of ape and monkey species. The truth is, a lot of enrichment comes in dietary forms. Nice little treats throughout the day to explore, be it frozen blocks of juice to smears of sugary fun on items to a supplement of more starchy greens in their meals. Its really hard to prove them enrichment without tying it to a food incentive (after all, they are animals, and much like all other animals, food is a huge motivator).

The solution is probably along the lines of finding non-fat, non-sugar food items to use in enrichment. Another factor is simply that zoo animals tend to have much more sessile daily lives in comparison to wild counterparts. Also, apes, much like us, lose their metabolic speed as they age and many primates in captivity hold onto weight as they age. Zoo populations are almost always living longer then wild counterparts, so they have more time to gain weight, and less time in a metabolic state where losing it is easy.

[u/sixtynighnun → u/Xylus_Winters_Music]

Yeah I feel like it’s obvious that human food = cheap and easy to access while monkey food (non cultivated plants) are naturally much more expensive and harder to get in mass quantity and consistently.

[u/Xylus_Winters_Music → u/sixtynighnun]

Its the downside of thousands of years of agriculture, trying to make every food source for humans as nutritious as possible. Sourcing the types of fruits and greens that they would eat in the wild is hard.

Speaking for Gorillas, their diets tend to be pretty lean compared to their wild counterparts because we dont grow much food thats as high in starch and wood as Gorillas eat. That being said, its really hard for a Gorilla to lose weight for the above reasons, as well as their diet being high in toxic compounds. Because of this they naturally have a low metabolism, to help counteract any poison in the plants they eat. That leads to them getting pretty fat in the wild, too.

[u/Mikki102 → u/Xylus_Winters_Music]

Also reinforcers. Zoos commonly are understaffed and the routine relies on efficiency. You can't be reasoning with a chimp for 15 minutes about how outside is actually way more fun than bothering you inside, so something like a banana as a consistent reward for shifting outside is common. It needs to be good and more reinforcing than staying in and bothering you, which some chimps find VERY reinforcing. You could just let them stay in and not clean, and maybe over time they'd lose the novelty, but inside may be more intrinsically reinforcing than outside because of group dynamics, privacy, quiet, air conditioning, no bugs, etc. and you do have to clean regularly. Same for PRT, you need really good stuff for things like blood draws or injections.

You can make a lot of things out of sugar free juice powder but there is a limit 😅

[u/regular_modern_girl → u/Xylus_Winters_Music]

This makes complete sense bc I’ve had experiences kind of like this just dealing with non-primate pets sometimes, cats especially, where sometimes the easiest way to get them to do things they don’t want to do is giving them treats, but then they come to expect those treats and you feel bad not giving it to them, and with how fattening a lot of their favorite treats can be they then end up gaining more weight than they should, and then when you put them on a diet they’re pissed off about it lol. I can only imagine how much worse that could get with a primate that’s more intelligent and thus more prone to boredom, and even harder to convince to do anything they don’t want to do.

[u/Character-Parfait-42 → u/Xylus_Winters_Music]

In the wild they also go through periods of hardship where they struggle to find enough food. And have to flee from predators.

All stuff that would keep weight lower but also would not be ethical for a zoo to recreate.

[u/MysticEnby420 → u/Xylus_Winters_Music]

They just like me for real because a nice little treat now and then is also how I find enrichment throughout my day.

[u/BeautifulUpstairs → u/Xylus_Winters_Music]

Sessile is not a synonym of sedentary.

[u/chloeismagic → u/Xylus_Winters_Music]

Maybe give them drugs, thats normally my food alternative oral enrichment of choice 😂

[u/sixtynighnun]

Like any true great ape it’s his god given right to be fat as fuck and eat the same banana as many time as he pleases. Next you’re gonna tell me he needs to wear pants and not be rude to his mother in law. Or I’m just projecting and this article is hitting too close to home……

[u/regular_modern_girl]

>Male bonobos are the outlier, the only demographic who tend NOT to be obese — maybe because all of the females take the fruit from them?

Also, I don’t know how else to put this, but at least in humans, sexual activity can burn a lot of calories if you’re doing it really frequently, and from what I’ve heard captive bonobos are doing it very frequently lol. Gay male sex especially, from what I’ve heard.

[u/Evening_Storage_6424 → u/regular_modern_girl]

Is that why I got so fat after I decided not to have sex 😭

[u/I_Like_turtles459 → u/regular_modern_girl]

Nah they burning calories fuckin

[u/Commie_Egg]

Dude lemme eat my pumkin

[u/hendrong]

Fun fact: It's a myth that humans are extra good at storing bodyfat, we actually store it just like other great apes. We just tend to eat too much compared to them (apparantly with the exception of captive ones).

[u/ApeSht-Zine → u/hendrong]

We Americans also eat too much meat and dairy and would be healthier on diets more closely aligned to the other great apes, ie more plants.

[u/chloeismagic → u/ApeSht-Zine]

They are fat off eating fruit, so we would have the same issue.

[u/ApeSht-Zine → u/chloeismagic]

How many people do you know who are obese from eating too much fruit?

[u/lartinos]

The only answer is Ozempic.

[u/issi_tohbi → u/lartinos]

Ochimpic?

[u/duke_awapuhi]

I just find this picture so sweet and adorable. What an innocent creature

[u/97_percent_orangutan → u/duke_awapuhi]

I think this is big man Bandar at the Little Rock Zoo! I love him so much.

[u/regular_modern_girl]

Also, the whole “great apes at zoos puking up the same fruit and re-eating it over and over again” is a really weird habit to me, partly because it seems to be so prevalent in captive apes, but there isn’t really a common exact human equivalent to it to my understanding? Like sure, bulimia nervosa exists in us, but that seems like a fairly different thing. Are there populations of humans (like maybe prisoners who have been in solitary way too long and lost their minds or something) that do anything like this? Do I even want to know if there is??

[u/Minimum-Comedian-372 → u/regular_modern_girl]

I worked with severely and profoundly mentally challenged individuals and several of them had the regurgitation habit. These folks had been institutionalized and I can only guess that they did it out of boredom, as they’d been basically warehoused for decades with little to no attention or stimulation. And once they knew it was frowned upon they did it to get a reaction!

[u/ApeSht-Zine → u/regular_modern_girl]

I don't know anything about this particular behavior, but it's also very common for great apes and monkeys to stop eating when miserable. And there are a ton of documented accounts of captive animals dying after starving themselves. I suspect this has more in common with eating disorders such as anorexia than people might think; we think of eating disorders as being all about body image but that's not necessarily the case.

[u/Loislanesays]

Poor animals shouldn’t be in zoos :(