Investigating Co-occurrence among Look-alike Species: The Case of Three Bears in Northeast India

Abstract

At the most basic level, the assessment of a species’ status involves knowing where it occurs. Determining the presence of rare species is difficult, and can be further confounded by the presence of a more common look-alike species. We investigated one of the few places in the world where three species of bears have been reported to co-occur at a fine scale: Balpakram National Park, Meghalaya, India. Asiatic black bears (Ursus thibetanus) are fairly common, and we sought to determine whether sun bears (Helarctos malayanus) and/or sloth bears (Melursus ursinus) also resided there. The local Garo language has words for three types of bears, and some local people reported the continued presence of a small type of bear, possibly the sun bear, but the probable extirpation of sloth bears. Because these bears look somewhat alike, local people and government forest officers could not provide convincing accounts of the presence of more than one species. We measured claw marks on climbed trees, a method used to differentiate sun bears from Asiatic black bears where both are known to occur; however, this method turned out to be unreliable for detecting sun bears where their presence was unknown because sun bear-sized marks are not distinguishable from juvenile black bears. We recommend targeted camera trapping near recent purported sightings of the other two bear species.