Your Monday Mammal: Mystery in Borneo

What is this mystery beast captured on film in Kayan Mentarang National Park, East Kalimantan, Indonesia in 2003? Initial claims were that it was a new species
of carnivore. But is there evidence for this claim?

Initial discussions centered on whether the specimen was a viverrid of some kind (e.g. the very rare Hose's Palm Civet, Hemigalus [Diplogale] hosei). The WWF, who sponsored the original research, for their part felt that this was most likely a new species of civet. Recently a study by
Meijaard et al. has analyzed the two available photos of the specimen (and in so doing generated this wonderful recreation)

The researchers scored the photos based on thirteen characteristics and then compared the scores with those for seventeen possible species (including H. hosei). The study concluded that the specimen was most like Thomas's flying squirrel (Aeromys thomasi, 12 of 13 matches) with the red giant flying squirrel (P. petaurista, 10.5/13) being the next highest match. And H . hosei? It only scored 4 out of 13.

(Interestingly A. thomasi was actually described by Hose in 1900 and H. hosei was described by Thomas in 1892!)

So while this is not a slam-dunk identification, it is more likely that the specimen is a large flying squirrel than a carnivore. As the authors note:

We recognize that traits identified from poor-quality photos can only be approximations of exact measurements and characters, but our hypothesis about the identity of the unknown carnivore can be tested by the collection of further field data ... We also recommend that wildlife photographers become more circumspect in announcing "new" species, especially with media that are only too willing to widely publicize such news. The WWF has taken the right steps towards formal description of the "new" mammal by attempting, so far unsuccessfully, to collect a specimen. This case highlights the importance of formal description based on type specimens and a review process. As recently stated by Timm et al. (2005), photographs are not valid substitutes for a type specimen. The function of a type specimen in nomenclature is to provide an objective basis for the application of a species-group name. Only once such a specimen is in place should there be media announcements about new species.

Ref: MEIJAARD, ERIK, KITCHENER, ANDREW C. & SMEENK, CHRIS (2006) 'New Bornean carnivore' is most likely a little known flying squirrel. Mammal Review 36 (4), 318-324. doi: 10.1111/j.1365-2907.2006.00089.x

[This is the first of a hopefully weekly series of posts on mammals]