Of course gorillas don't eat the same in zoos as they do in the wild. In the wild they mainly eat leaves, grasses, stems, herbs, root and bark and fruits when available. Sometimes they also eat termites and (usually 'unintentionally') small insects; these are among the green they eat. They eat 20 to 30 kilos a day.
In zoos they eat a variety of vegetables, grass, leaves and bark. They rarely or never eat fruit; it's different per zoo. The reason is that our fruit contains sugars to make it tasty for us. This is of course not the case in the fruits in the wild. I often hear people say (for example to their children) that gorillas eat bananas. That is not the case in zoos! But even in the wild gorillas don't eat bananas; the banana is not found where they live. The banana originally is from Asia. It is grown in many countries worldwide for years now. In Cameroon, for example, where the western gorillas lives. So the people who have banana plantations there sometimes have/had problems with gorillas coming to eat from their harvest.
Funny by the way, both children and adults often mistake chicory for a banana. They get chicory very often in zoos I visit, so it's something I hear a lot.
As mentioned, in some zoos they do get fruit. In the past also in Apenheul. There often were slices of apple fed during feeding presentations. That was because it's easily to throw across the water. I haven't seen it in recent years luckily. In Antwerp they still get a little bit every day. When I was in Blijdorp on 29 January 2016, they gave the gorillas kiwi. When I was chatting with a caretaker, he told me that a whole load of kiwis had arrived and then the gorillas also got an extra treat. On 17 February 2016 I also saw kiwis in Burgers' Zoo! But (luckily) it isn't common. Mainly it's used when a gorilla needs medication. More about that sugar below.
When it comes to vegetables, I've seen a lot giving to the gorillas. Most common are: endive, cucumber, zucchini, carrots, bell peppers (they prefer the red ones), onion and chicory. But they also get kale, tomatoes, red beets, fennel, leeks, broccoli and kohlrabi. And much more.
In addition (and everything is different per zoo) they also get branches with leaves, lucerne, seeds and especially for herbivores made kibble. It is especially funny/special to see how they patiently pick up small seeds from the floor and eat them. For example: the gorillas in Burgers' Zoo occasionally get corn grains and to see a ± 160 kilos heavy silverback so calmly, patiently and carefully pick those grains off the ground one by one ... it's so nice to see.
The gorillas in some of the zoos I visit sometimes get a hard-boiled egg. I have also seen boiled potatoes passing by here and there. Bao Bao regularly gets sweet potato. In Antwerp Zoo they regularly get boiled rice. All in all, very varied.
From the branches they get they eat the leaves and scrape off the bark and eat that. I once heard years ago that it is (among others) to take care of their teeth. When I started making this website I thought 'I'll look it up on the internet', but I couldn't find anything about it. When I saw a 'gorilla expert' (zoologist in a Dutch zoo) on 5 February 2016, I asked her. She told me that it is 'just' high fiber food, which (to my surprise) is also digested well.
I once saw sauerkraut in Burgers' Zoo. Well, they checked it from a distance and decided not to even try it. They didn't know it and ate all the other food. Until all was eaten, some members of the group started to investigate it.
In zoos, youngsters have to be very smart (and fast) to actually eat their food. The older members of the group shamelessly take away very tasty food. Even if the youngsters have put it in their mouth, someone else (often the mother who is generally close to the little one, but also other group members) will even take it out of the mouth. It is only safe once swallowed. I have regularly seen a larger gorilla just grab such a small one tightly or push it to the ground and open its mouth to take it out. Fortunately, those youngsters still get to drink mother's milk until they are 3 to 4 years old, so they get more than enough. Does it also happen in the wild, that taking food from a youngster? I guess not; there they sit between their food so there is more than enough. Here a photo of Bao Bao who took food from his son (22 July 2022). Most of the times Kiango can eat food he gets his hands on (even if he kind of stole it, because he was faster than daddy to take it), but Bao Bao really wanted to have this himself so he took it away.
Once I saw a poster with vegetables and fruit on it in Apenheul. On it you could see how much sugar is in various products. I took a photo of it of course.
For a better view, I cut out the various products:
