Delving into the past of a big cat: Clouded leopard redefined

As shown in 2006, the genus Neofelis comprises two species living with distinct distributions. Clouded leopards from Borneo and Sumatra are genetically and morphologically highly distinct from their relatives on the mainland (Neofelis nebulosa) and thus form a separate species, the Sunda clouded leopard (Neofelis diardi).

Following up on these findings, a team of researchers led by Andreas Wilting and Joerns Fickel of the IZW collected fur and bone samples of the clouded leopard from natural history museums worldwide, with the aim of elucidating to what extent the spatially distinct populations of the Sunda clouded leopard have followed different evolutionary paths. "Although we suspected that Sunda clouded leopards on Borneo and Sumatra have likely been geographically separated since the last Ice Age, it was not known whether this long isolation had caused them to split up into separate sub-species," explains Wilting.

In the course of their study, the researchers were able to demonstrate considerable genetic differences between the two populations. Dissimilarities between populations were also found with regard to skull morphology, as shown by Per Christiansen of the University of Aalborg, Denmark, a co-author of the study. In contrast, a comparison of coat colour patterns conducted by Andrew Kitchener from National Museums Scotland yielded only small deviations between the populations -- the authors surmise that this finding could be attributed to the highly similar tropical habitats on Borneo and Sumatra. Based on these distinct patterns of genetic and morphological variation, the researchers have now formally described two subspecies of the Sunda clouded leopard: one occurring exclusively in Sumatra, the other being endemic to Borneo.

"So far we can only speculate about the specific course of events in the evolution of the clouded leopard," says Joerns Fickel. The scientists postulate that natural disasters and global climate periods are responsible for the split into two species and subspecies. The eruption of the "super-volcano" Toba on Sumatra ~75.000 years ago is likely to have played a particularly important role in this process. As Fickel explains, this event unquestionably had extreme consequences for the Southeast Asian fauna and flora. On that account, the researchers conclude that in all likelihood, only two populations of clouded leopards survived the eruption, one in southern China (Neofelis nebulosa) and one on Borneo (Neofelis diardi). In a plausible scenario, the latter recolonised Sumatra via glacial land bridges and subsequently developed into a different subspecies as sea levels rose after the last Ice Age and isolated the two islands.

Both subspecies are classified as endangered by the IUCN, owing to the fact that they, as all other big cats, occur at low population densities and require big home ranges for their survival. In order to save the Sunda clouded leopard, it is therefore of paramount importance to protect large forest areas in Borneo and Sumatra, or at least to manage them sustainably, Wilting emphasises. For this reason, the project is being carried out in close collaboration with Sabah Wildlife Department in the Malaysian state of Sabah in Borneo. Dr. Laurentius Ambu, director of the Sabah Wildlife Department, adds that the IZW together with his department has contributed actively to efforts for the conservation of the Sunda clouded leopard in Borneo for several years, and last year, this team published the first video footage of a Sunda clouded leopard from the wild.