Understanding of object properties by sloth bears, Melursus ursinus ursinus

Abstract

Recent studies have shown that several species within the Carnivore order show impressive cognitive skills. However, bears, especially sloth bears, have received little attention with regard to their cognitive abilities. Here we presented seven sloth bears with three tasks to test their object permanence, short-term memory and ability to use acoustic cues to infer food location. In the object permanence test, subjects saw an object disappear in one of the three holes of a tree trunk. Bears retrieved the food in the correct hole significantly above chance, suggesting that they have some basic understanding that objects continue to exist even when they are not visible. To study sloth bears' short-term memory, we used different time delays (30 s, 60 s, 2 min) between the object's disappearance and the subject's retrieval. Bears performed at chance levels in all conditions. In the acoustic cues test, the experimenter shook one of two identical opaque containers, only one of which had been baited: when the baited container was shaken, this made a noise and thus revealed the presence of food inside; when the unbaited container was shaken, there was no noise, revealing by exclusion the presence of food in the other container. In both cases, bears selected the baited container significantly above chance. As sloth bears are a mainly insectivorous solitary species, good performance in the object permanence and acoustic cue tests suggests that their cognitive skills may be the result of foraging challenges rather than social ones. Failure in the short-term memory test, instead, may suggest that memory for short-term punctual events has little evolutionary significance for bears, although further studies are needed to draw definitive conclusions.