Juvenile Growth, Development, and Learning

We examine whether orangutans extremely long juvenile period (7-8 years) is a response to their variable environments and long periods with very low food availability. We are using new technology and research techniques in concert with ongoing behavioral observations of wild orangutan behavior to study the ecological risk aversion hypothesis. In order to study orangutan growth we built a parallel laser camera. We use a laser mounted camera to project two parallel lasers (human and animal friendly) on the orangutan and then take a picture. This gives us a known distance, and a digital tape measure, which we can use to measure limb lengths and other body parts. We can measure changes in wild orangutan growth rates and can see which factors affect growth rates, for example changes in food intake. 

In addition, we also collect fecal samples, examine chewing efficiency, and measure nursing rates. We can learn about offspring milk intake from fecal samples. Mother’s milk contains different levels of carbon and nitrogen than plant foods, which allows us measure ratios of carbon and nitrogen isotopes in fecal samples and compare these differences between mother and offspring. Our findings improve our understanding of the ways orangutans have adapted to their rainforest environment through long periods of juvenile development.