Scientists Say: Kleptotrichy

Kleptotrichy (noun, “KLEP-toh-trik-ee”)

Kleptotrichy is the act of stealing hair from live mammals. Some birds use the behavior to gather fur to line their nests. The word is a based on two Greek words: klepto (to steal) and trich (hair).

People have long known that some birds line their nests with fur. For many years, scientists thought birds used hair that mammals had shed into the environment. Mammals shed hair regularly, leaving individual hairs behind as they travel. During a seasonal molt, some mammals drop the hair they shed in clumps, making it easy for birds to collect.

But some birds don’t wait around for their furry companions to molt. They don’t search for a carcass to raid, either. Instead, they go straight to the source, plucking fur directly from the live mammal’s body.

The birds most likely to engage in kleptotrichy are members of the Paridae family. That includes chickadees and titmice. These plucky little birds will circle a resting mammal to see if it’s going to react. Once the coast seems clear, they moving in to gather fur.

Birds have been spotted stealing hair from raccoons, foxes, livestock, and even people. Often the mammal is asleep when the bird approaches. But these thieves don’t always wait until nap time. One brave little bird was spotted pulling fur from a raccoon’s backside while the furry bandit helped itself to birdseed. Although the raccoon swatted at it now and again, the titmouse got away with many mouthfuls of fur.

Kleptotrichy is more common in temperate regions where nights can get cold. It happens less often in the tropics and subtropics. The regional difference suggests that the hair helps to keep eggs and nestlings warm at night. Or perhaps the mammal smell helps discourage predators from attacking the nest.

In a sentence

Chickadees and titmice will pluck fur from sleeping mammals, an act called kleptotrichy.

Check out the full list of Scientists Say.