If I told you that the surface area of a sea otter could cover a professional hockey rink, you might

If I told you that the surface area of a sea otter could cover a professional hockey rink, you might be forgiven for being a little confused, as these charming creatures are only a maximum of about 1.5 metres long. The secret lies in their fabulous fur coats, which are some of the densest in the animal kingdom. An adult male may have up to 800 million hairs on its body (for comparison, we have only about 100,000 hairs on our head!). Fascinating new research has found that body hair such as this can increase the surface area of animals by up to 100 times. This means that not only would a sea otter’s true surface area cover a hockey rink, but your cat could cover a ping-pong table, and a honeybee a slice of toast. The aim of the study was to assess how body hair affects an animal’s ability to stay clean. While it is clear that having fur greatly increases the potential surface area available to pick up dirt, it also acts as a shield that keeps particles away from the body and makes them easier to remove by actively grooming, shaking or secreting chemicals, or by passive displacement of dirt. Mammalian eyelashes, for example, act to redirect air flow and help to prevent dirt from being deposited in the eyes.

Ref: Amador & Hu, 2015. Cleanliness is next to Godliness: mechanisms for staying clean. Journal of Experimental Biology 218: 3164-3174 [link]