Clouded leopards—named for their large, cloud-like spots—are rare. They are medium-sized (a bit bigger than a housecat) tree dwellers with big teeth and big paws that let them hang upside down among the foliage. In 2006, scientists used DNA studies to determine that there were two species of clouded leopards: Neofelis nebulosa, which lives on the Asian mainland and is the subject of a breeding program at the National Zoo (producing some of the world's most adorable kittens), and Neofelis diardi, the Sunda clouded leopard, found on the islands of Borneo and Sumatra.
Now a group of researchers led by the Leibniz Institute for Zoo and Wildlife Research in Germany has determined the the Borneo and Sumatra populations are really two separate subspecies, splitting this rare kitty into two even rarer varieties. The scientists, reporting in Molecular Phylogenetics and Evolution, analyzed DNA from 15 leopards on Borneo and 16 on Sumatra and also examined the skulls and coats of museum specimens. They found that the kitties on the two islands looked very similar on the outside but had significant differences in skull shape and in their genetics.
The scientists aren't certain about the events that led to the evolution of the various species and sub-species, but here's what they propose: The ancestor species to all modern clouded leopards was living in Southeast Asia when the super-volcano Toba erupted on Sumatra around 75,000 years ago, possibly plunging the Earth into a years-long volcanic winter. Two populations of clouded leopards survived—one in southern China, which evolved into the modern-day clouded leopard, N. nebulosa, and one on Borneo, which became the Sunda clouded leopard, N. diardi. When sea level was low, some of those Sunda clouded leopards were able to travel back to Sumatra, but when the last Ice Age ended, around 10,000 years ago, and sea levels rose, Borneo and Sumatra were once again isolated from each other and the two populations were left to evolve into sub-species apart from each other.