Craniometric differences among Malayan sun bears (Ursus malayanus); Evolutionary and taxonomic implications

In this paper I use multivariate statistical analyses of Sun Bear (Ursus malayanus) skull measurements to investigate the differences between specimens from Borneo, Sumatra, the Malay Peninsula, and the Asian mainland. Specimens from Borneo were significantly smaller than those from elsewhere, but they had relatively long tooth rows. There were no significant differences between specimens from Sumatra, the Malay Peninsula and the Asian mainland. Based on these results, the interpretation of the fossil record, and some preliminary molecular work on the species, I hypothesize that U. malayanus originally evolved in the Sundaic Subregion some time during the Pliocene, and that soon after the species was split in a Malayan and a Bornean form. The Malayan form later dispersed to the Asian mainland and Sumatra. The observed morphological differentiation of the Bornean taxon from the others warrants its subspecific designation as U. malayanus euryspilus. I recommend assigning all remaining populations to the typical form U. malayanus malayanus. Although more research is needed, especially on the species' phylogeny, the results imply that the two subspecies should be independently dealt with in conservation management.