119.2 Saturday, Jan. 7 Wet mammals shake at tuned frequencies to dry HU, David*; DICKERSON, Andrew; MILLS, Zack; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology firstname.lastname@example.org
In cold wet weather, mammals face hypothermia if they cannot dry themselves. By rapidly oscillating their bodies for fractions of a second, hirsute mammals can shed water droplets in a manner similar to the spin cycle of a washing machine. High-speed film and fur particle tracking are used to characterize the shakes of over twenty zoo animals ranging in size from mice to bears. We here report a wet-dog-shake rule for shaking frequencies according to body size, and test this rule using experiments with a wet-dog simulator and predictions from capillarity. We find the frequencies observed are roughly consistent with those required for drop ejection, found by considering the balance of surface tension and centripetal forces on drops adhering to the animal. We also find a novel role for loose mammalian skin: by whipping around the body, it increases the speed of drops leaving the animal and the ensuing level of dryness relative to tight skin. The tuning of mammalian shakes to shed water demonstrates an inability to shed contaminants such as crude oil.