When Elok, our male Sumatran orangutan, came to the Oklahoma City Zoo in 2000, he was spunky, energetic and little – weighing in at just 60 pounds.

Now, at 19 years old, Elok is an impressive adult who tips the scale at 350 pounds. From an animal health perspective, 350 pounds is considered overweight for a male orangutan, as the average weight of a male his age is approximately 250 pounds. To ensure optimal health and fitness, Elok’s caretakers encouraged exercise and the veterinary team made various dietary adjustments. Despite these strategies, however, Elok’s weight did not decrease.

Elok’s caretakers observed that his energy levels were low, and he didn’t display signs of interest in interacting with his female companion, Negara. Because being overweight can be detrimental to the health of any species, especially orangutans who are closely related to humans, we knew that it was critical to understand why he wasn’t losing weight like he should’ve been. 

One of the amazing things about Elok is his intelligence, he is incredibly smart. As an infant, Elok was hand-reared, so he is very familiar with his human caretakers. These two factors are ideal for medical husbandry training, which is a form of training that encourages animals to participate in their own healthcare. Elok had already been trained to voluntarily give blood, so the veterinary team was able to collect blood and submit it for a variety of blood tests looking at his white blood cells, various chemistry panel results as well as some metabolic and hormone testing. Because of the excess weight and lack of energy and activity, the veterinary care team was concerned that Elok may have an underlying medical condition, specifically a metabolic disorder.

All of his basic blood values were normal but there were some very minor abnormalities with his thyroid hormone levels. There is not a lot of information available on normal thyroid levels in orangutans, especially in different age groups, so we often have to use normal values for humans as a comparison.  Even though orangutans are closely related to humans, there are still significant differences, so some caution must be used when comparing these results.  However, based on Elok’s clinical presentation and mild changes in blood values, we diagnosed him with probable hypothyroidism, also referred to as underactive thyroid.

From there, Elok began a trial of thyroid supplementation medication to see if it would result in weight reduction and an increase activity levels. Much to our surprise and delight, Elok’s energy quickly increased. He began interacting more with Negara, and exploring his outdoor habitat and amazing, new climbing structure. As a result, the pounds started melting off!  To date, Elok is down about 50 pounds and feeling great. Because he is trained for voluntary blood collection, we are able to monitor his thyroid values very closely and adjust medications accordingly to keep his hormones in a stable range.  The increase in his activity level and reduction in his weight will keep Elok healthy for years to come.

- Director of Veterinary Services, Dr. Jennifer D’Agostino

Photos: Andrea Johnson