Kleptotrichy: Birds Who Steal Fur

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Videos of small birds plucking hair from sleeping dogs, foxes, raccoons, and other mammals can easily be found on YouTube. Aside from the cuteness factor of a small bird stuffing its beak full of soft fur from the unsuspecting back of a sleeping predator, scientists recently published their findings on where and why birds engage in this somewhat risky behavior.

This behavior in birds has been little studied by researchers. A recently published article in Ecology found only a few anecdotal accounts in scientific literature on the plucking of mammalian hair from live animals by birds.

The researcher’s literature review only pulled up 11 published accounts covering six species that were observed to engage in fur-plucking from live animals.

For example, a 1949 note in the Journal of Mammalogy recounted the author’s experience of seeing an intrepid titmouse that vigorously yanked fur from the tail of a possum.

More common are accounts from citizen scientists who have posted videos to various social media sites showing birds busily plucking fur. The researchers found 99 videos on YouTube pulling fur from mostly dogs but also other animals and even pulling hair from humans. In total those 99 videos showed mostly titmice plucking fur and hair from 47 humans, 45 dogs, three cats, three raccoons, and a porcupine

Various species of titmice seem to be the most commonly observed birds that pull fur.

Tufted Titmouse (Baeolophus bicolor).
Tufted Titmouse (Baeolophus bicolor). Photo: National Park Service, Public domain.

While fur and hair plucking is risky behavior, most anecdotal accounts and videos show sleepy animals that seem unaware or unbothered by their smaller trespassers.

Pollock et al. coined a new term for this behavior, calling it “kleptotrichy” (from Greek “klepto-” – to steal + “trich-” – hair). This is a similar term to the similarly known term  “kleptoptily” which is the theft of feathers from other birds.

Why Do Birds Pluck Fur?

Birds typically pluck fur to line nests. The researchers of the Ecology study note that hair, fur, or wool insulates nests which then improves nestling survival and recruitment in colder areas, so this widespread practice could be adaptive.

The smell of fur from predators can also be a deterrent to would-be nest robbers.

References

Packard, F. M. (1949). Tufted Titmice Pull Hairs from Living Mammals. Journal of Mammalogy30(4), 432–432. https://doi.org/10.1093/jmammal/30.4.432-a

Pollock, H. S., MacDonald, S. E., Vizentin‐Bugoni, J., Brawn, J. D., Sutton, Z. S., & Hauber, M. E. (2021). What the pluck? Theft of mammal hair by birds is an overlooked but common behavior with fitness implications. Ecology, e03501. https://doi.org/10.1002/ecy.3501

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