People who have seen Burrito in person often comment that he’s “fluffier” than the other chimpanzees at the sanctuary, and it is an accurate observation. The technical term for this fluffiness is piloerection. A chimpanzee is said to be pilo erect when his or her hair is standing on end due to anxiety or excitement. (Humans also experience piloerection when we get goosebumps, but it’s not as obvious since we have less hair.) When a chimpanzee is completely calm and relaxed, his hair lies flat against his body. Given that Burrito is rarely completely calm — he’s a pretty high-strung guy — it makes sense that he’s very often pilo erect.
I like the following photos because you can see how much of Burrito’s impressive size is body and how much is “fluff”.