Few scientists have ever seen the rare tufted ground squirrel (Rheithrosciurus macrotis), which hides in the hilly forests of Borneo, but it is an odd beast. It’s twice the size of most tree squirrels, and it reputedly has a taste for blood. Now, motion-controlled cameras have revealed another curious fact. The 35-centimeter-long rodent has the bushiest tail of any mammal compared with its body size.

"The species is really quite bizarre," says Erik Meijaard, a conservation scientist with People and Nature Consulting International in Jakarta.

Meijaard and his wife, Rona Dennis, an independent remote sensing scientist, gathered a collection of photos of Rheithrosciurus, including ones from colleagues. All were snapped by motion-activated cameras. Their 15-year-old daughter Emily Mae Meijaard, a student at the British International School, Jakarta, analyzed the pictures, measuring the size of the tail and body of various individuals.

Rheithrosciurus's plush tail is 30% larger than the volume of the squirrel's body, the family reports this month in Taprobanica. "This squirrel takes everything to the extreme," says Melissa Hawkins, a mammalogist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C., who notes that the ears are particularly hairy as well. The closest contenders, whose tails are merely as bulky as their own bodies, include the common striped possum, which has a prehensile tail for climbing; the squirrel glider, which navigates with its tail as a rudder; and the ring-tailed cat, which uses its tail for balance during acrobatics in trees.

It's not clear why Rheithrosciurus needs so much tail, but Emily Mae and her co-authors believe the bobbing mass of fur might confuse clouded leopards and other predators, or prevent them from getting a good grasp when they strike. That idea sounds plausible to Hawkins, who says that when her field crew saw the squirrels in Borneo, they at first thought it was a much larger animal.

Local legends suggest that Rheithrosciurus, which is thought to mostly eat giant acorns, can be savage. Hunters say that the squirrels will perch on low branches, jump onto a deer, gash its jugular vein, and disembowel the carcass. "It sounds pretty fantastical," says a skeptical Roland Kays, a zoologist at the North Carolina Museum of Natural Sciences in Raleigh. "Even more than its fluffy tail."

Emily Mae, in any case, has switched her focus to photographs of something less gruesome: the mating behaviors of the argus pheasant.