Originating from central Africa, gorillas are among the largest of all the primates. To maintain this bulk, they need to consume vast amounts of food and spend a large portion of their day eating. In captivity, this has led to gorillas' becoming overweight and generally unhealthy, although recent initiatives have been begun to reverse this trend.
Despite their sometimes fearsome appearance, gorillas are primarily herbivorous creatures. Wild gorillas use their powerful jaws to eat the tough stems of saplings and shrubs while also feasting on leaves, vines and -- very occasionally -- small animals. Western lowland gorillas who live in the more tropical areas incorporate large amounts of fruit into their diets also. All gorillas kept in zoos in the United States are western lowland gorillas.
Health Problems for Zoo Gorillas
There have been concerns raised by animal rights groups that gorillas kept in captivity in zoos have been experiencing major health issues thanks to their poor diet. Researchers at Case Western Reserve University discovered that the number one killer of gorillas in North American zoos is heart disease. They also discovered that this disease can be traced back to the types of food being fed to them by zoo keepers. They found that gorillas were being fed bucket loads of feed with ultra-high levels of sugar starch and vitamins to replicate the nutrients of the food they would eat in the wild. This unnatural diet was leading to gorillas' becoming overweight and experiencing heart problems.
Until recently, zoo keepers would supplement the diet of gorillas in their care with Purina High Protein, HMS High Fiber Primate, Zu/Preem Primate Dry and Purina Lab diet in an effort to replicate the nutrients of their wild diet. In addition to these synthetic nutrients, six North American zoos fed their gorillas meat, 19 fed theirs eggs, 18 fed milk to their gorillas and 21 added yoghurt to their diet. These unnatural additives to gorilla diets were identified as a cause of their heart problems, which is understandable when you take into account the 50 to 60 per cent of the day gorillas spend eating.
Elena Hoellein Less, a doctoral student at Case Western Reserve University, theorised that a reversion to the diet they would experience in the wild would help combat these problems, rather than trying to synthesise these nutrients. At the Cleveland Zoo where she conducted her research they now feed their gorillas romaine lettuce, dandelion greens, endives, alfalfa, green beans, flax seeds and tree bark. This change in diet has caused the gorillas to lose 29.5 Kilogram each, making them way more like wild gorillas.