Ferrets (Mustela furo) Are Aware of Their Dimensions

Self-awareness is a complex phenomenon expressed as the ability of an individual to separate "self-entity" from "other entity". One of its earliest evolutionary components is body size awareness, namely, the ability to consider the boundaries of one's own body as factors influencing interaction with surrounding objects. For ferrets, Mustela furo, the task requiring the penetration of various holes is ecologically relevant. We designed an experimental study in which the ferrets were supposed to select one opening out of three to get the bait. The first experiment was aimed at studying whether ferrets would prefer the holes basing on the hole size. In the second experiment, we tested the ferrets' ability to select a single passable hole on the first try while the impassable ones were larger in area. Results from the first experiment show that when choosing from the three passable openings, the animals preferred the shortest path to the bait and ignored the size of the holes. In the second experiment, all tested ferrets preferred to penetrate the passable opening on the first attempt, even though the areas of the two impenetrable ones were larger. We argue that these data indicate that ferrets are aware of their own body size.