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Something Mysterious Is Killing Captive Gorillas

KRISTA LANGLOIS: ‘In 2006 three beloved male gorillas from 21 to 34 years old died in quick succession… at the Cleveland Metroparks Zoo… The culprit turned out to be heart disease… Unlike humans, gorillas with heart problems didn’t show evidence of coronary-artery blockage or high cholesterol… Elena Less, an associate animal curator at the Cleveland Zoo,… found that their “biscuit diet” left plenty to be desired. While gorillas are genetically similar to humans, they have very different digestive systems — more akin to those in horses. Like horses, gorillas are “hind-gut digesters” who process food primarily in their extra-long large intestines rather than their stomachs. That means they’re great at breaking down fiber, but not so good with sugars or grains…

Plus, wild gorillas spend up to 70 percent of their time foraging for high-fiber plants, while gorillas on the biscuit diet can scarf down their food in just 30 minutes. Kristen Lukas, director of conservation and science at the Cleveland Zoo and chair of the Gorilla Species Survival Plan, thinks this might contribute to a behavior called regurgitation and re-ingestion, in which animals intentionally bring up their food and eat it a second time. The behavior has never been recorded in wild gorillas, but it’s well documented in humans with developmental disorders — and in some two-thirds of captive gorillas. Lukas has found that gorillas that regurgitate are actually better adjusted than other captive gorillas in terms of behavior and stress; the behavior may be an adaptation that gives them a sense of control, or allows them to better mimic the amount of time they’d spend eating in the wild.

When Less switched the Cleveland gorillas to a new diet — one that cuts out biscuits and simple starches and replaces them with leafy greens, alfalfa, and branches from willow and other trees—she realized gorillas needed to eat about four times as much by weight as they had previously been fed. Not only did gorillas on the “Cleveland diet” get a huge increase in fiber, they spent nearly as much time eating as they would in the wild. Almost immediately, the Cleveland gorillas stopped regurgitating their food. “We thought the diet change might have an impact on regurgitation and re-ingestion,” Less says. “But to see it eliminated completely was shocking”.’ SOURCE…

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