Food washing in captive North American river otters (Lontra canadensis)

Descriptions of food-washing in non-human animals are rare and often misinterpreted. For example, the commonly described "food-washing" by raccoons has been experimentally shown to be unrelated to cleansing and may instead be an artifact of captivity. I observed a captive North American river otter seeming to wash his food and investigated whether captive otters (1) washed food to remove sand; (2) carried food to water to specifically remove a loose substance from food or to also remove an outer shell; and (3) associated washing with a specific location (their pool), or would wash food at another location (a tub near the pool). I found that the otters (1) used water to wash sandy food more often than clean food; (2) did not carry food to water for manipulations when removing it from artificial toys and from natural shells; and (3) one of two otters washed in the tub when food was offered closer to the tub, but otherwise preferred to wash food in his pool. Other behaviors, such as swishing food, dropping food in water and retrieving it, pushing it through water, rolling with it in water, and rubbing it against rocks may have aided in food cleansing. In contrast to published results from testing individuals of other species, captive otters truly wash their food.