While visiting the St. Louis Zoo today I photographed a young orangutan trying on a t-shirt. It was a delightful display, though not unexpected, given the long-documented tool-use of orangs:

Many wild orangutans have developed an amazing ability to use tools to help them exploit what food they can find. They’ve been observed using probes like twigs to extract insects and honey from tree trunks (held in their hands or their teeth), as well as blunt tools to scrape seeds from spiny fruit cases.

In addition to food-gathering tools, wild orangutans have been observed making tools to scratch themselves, fashioning leafy branches into “umbrellas” to shelter themselves from sun and rain, and using branches as swatters to repel bees or wasps that are attacking. Many have also been seen using “leaf gloves” to handle prickly fruits or branches, or creating “seat cushions” to sit comfortably in thorny trees.

Tool use hasn’t been observed in all orangutan populations, and it shows great variations even when it exists. This suggests to scientists that tool use is the result of innovation and learning that’s passed on from one generation to the next – one of the hallmarks of culture.