Isotopes in Feces Shed Light on Gorillas' Diet

Isotopes in feces samples of gorillas may shed light on their diet, a new study finds.

A team of researchers carried out a study to find out what the wild mountain gorillas in Uganda's Bwindi Impenetrable National Park ate over a period of one year, which could offer an insight as to how the animals adapt and survive in changing environments, reports phys.org.

For their study, the research team took samples of feces from gorillas during a period of one year from 2002-2003. They also collected samples of food that the animals might have eaten - fruits, wood, leaves and plants.

The samples were subjected to chemical analysis, revealing the isotopes of the food consumed by the apes. Isotopes are variants of a particular element and are present in different types of food. Various types of food have different levels of isotopes. By measuring the isotopes, researchers were able to determine what the apes ate over a period of one year.

They found that the Ugandan gorillas consumed more fruits between February and March and then from June to July.

While isotopes in hair, tooth enamel and animal bones have been analyzed to measure the diet, these techniques require the animals to be captured and tested. But the new study shows an easy way of measuring isotopes, just by analyzing the feces of the apes.

Using feces instead of animal tissue gets at shorter-term changes in diet, ecologist Donald Phillips, of Oregon State University, told ScienceNews. "It's a lot easier to get samples than if you had to capture a gorilla every time," he said.

Researchers point out that the isotope measurement using feces is a useful technique, but could not be considered as a replacement for field experiments, as they do not exactly reveal what food the apes ate and the information about the nutrition value of the food.

The findings of the study, "Detecting intraannual dietary variability in wild mountain gorillas by stable isotope analysis of feces", are published in the journal of the Proceedings of the National Academy of Sciences (PNAS).