Uncovering the cultural knowledge of sanctuary apes.

Behavioral differences observed between wild communities of the same species have been called "cultures" by some researchers who aimed to underline the similarities with human cultures. However, whether these differences truly result from social learning processes is debated. Despite promising recent research, data acquired in the wild still fail to exclude genetic and ecological factors from being potential explanations for the observed behavioral differences. A potential way to address this problem is through field experiments where communities of the same subspecies are exposed to identical apparatuses. This way, genetic and ecological factors can be controlled for, although their influence cannot be fully excluded. Working with wild-born Sumatran orangutans originating from two genetically distinct populations, we recently combined field experiments with captive work to show that genetic differences could not account for differences in their knowledge of stick use. Additionally, we found evidence that our subjects arrived at the sanctuary with a knowledge that they acquired but could not express in their community of origin. These findings suggest that animal cultures must also be analyzed at the cognitive level. Only in this way can we understand the true extent of animal cultures and how they relate to human cultures.