Mystery pygmy flying Squirrel on Borneo

Our guide saw this (Hose’s) pygmy flying squirrel landing in a tree 5-7 meters from the road in Deramakot (Borneo). This animal shows a completely clear white cheek and was very small, making us think of Emily’s. We are aware of the fact that there is only 1 sighting which is never confirmed to be an actual species.  Any second opinions would be appreciated!

Post author

Joep Duijvestijn


  • Jon Hall

    Great picture which I suspect was hard to take! Those cheeks do look very white but otherwise it looks very like Hose’s … I guess you have to wonder whether the Lesser Flying Squirrel is really a species at all given my understanding it was described on the basis of two animals 120 years again and never seen again. So the idea that the “pure white cheeks” are somehow diagnostic must be based only on those two skins. The animal in your picture does look very small but it also looks like it might be young…. So … basically… I have no idea 🙂 but it would be great to hear from people familiar with Hose’s about whether this picture would be very unusual if it was a Hose’s … I will share it with a couple of squirrel people and get back to you here.

  • Joep Duijvestijn

    Last night we had a new short sighting! This time behind our Homestay in Sukau, Kinabatangan River. Very short sighting with 2 glides and a run up the tree but unfortunatly no photo’s where taken. Looked like it was the same size or maybe a little bit bigger. We did hear it this time! Very high pitched: Iee iee iee without a rhytm really.

  • Jon Hall

    Hello again Joep, I passed this to a friend at the Smithsonian who sent it to another person who works on Bornean squirrels. Neither her, nor her post doc student. thought it could well be P hosei. But they also noted its a great picture of this species. Thanks for sharing.

  • hankgmedia

    Hi Jon,
    Thank you for sharing your knowledge on this thread, and I look forward to hearing any further insights you may have on the matter.

    I was recently on a trip to Borneo, and photographed what I believe to be the same species during a night walk in the Danum Valley. It was only a couple inches in length and was spotted ~30ft/10m off the ground. You can find my photo here:

    Our guide was incredibly excited because he has never seen the species in his several years as a guide in the area. After conferring with his fellow guides, they decided it was some kind of Pygmy flying squirrel endemic to Borneo.

    As far as I can tell, it is the same species as the one pictured above. While it does possess similar characteristics to Hose’s, it does appear to be a distinct species. Is there any further documentation for this species? If not, is this an undocumented species, endemic to Borneo? Thank you for any information you (or your colleagues) can provide.

  • Daan Drukker

    Exciting stuff. @hankgmedia, do you have any extra photos? I wonder how the tail tip of your specimen looks like. @Jon, do I understand correctly that the people from the Smithsonian indeed believe that Joep’s specimen is an emiliae and not a hosei?

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