The Bornean tufted ground squirrel became known as the 鈥渧ampire squirrel鈥� because of tales of it slashing the jugular veins of small deer. But the first study of the animal鈥檚 feeding habits has found it is a highly specialised seed eater feeding on very hard seeds produced by just a few trees.
鈥淰irtually nothing else in the forest is capable of eating them,鈥� says Andrew Marshall at the University of Michigan. 鈥淚t鈥檚 pretty rare to have a specialised seed feeder on one plant or subset of plants. The squirrels are far more specialised than any of the 80 other species we looked at.鈥�
Marshall is part of a team that has for decades been studying the relationships between species in the forests of Gunung Palung National Park on the island of Borneo. He and his colleagues have now put together all the data on the tufted ground squirrels (Rheithrosciurus macrotis) to produce the first scientific study of their feeding habits.
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鈥淲e don鈥檛 know all that much about them,鈥� says Marshall. What we do know is that they are unusual in several ways. The squirrels have saw-like incisors, unlike any other mammals, and , making them seem much larger than they are.
鈥淚t鈥檚 quite menacing, if a squirrel can ever be said to be menacing,鈥� says Marshall.
They are also most closely related to a group of squirrels found in South America, so how their ancestors reached Borneo is unclear. 鈥淭hey are a kind of enigma,鈥� says Marshall.
The squirrels came to the internet鈥檚 attention in 2014, after called them 鈥渧ampire squirrels鈥�. This moniker was based on stories told by the local Dayak people, who say the squirrels jump on the backs of deer and kill them by slashing their jugular veins. They then disembowel the deer and eat the stomach contents, heart and liver.
But Marshall鈥檚 team has never seen this happen. On the 79 occasions his team observed the squirrels feeding over the years, in 60 cases they were eating the extremely hard seeds of a big canopy tree called Canarium decumanum. On the other 19, they were eating similar seeds produced by a few other trees.
But while he thinks it is unlikely that the tufted squirrels attack deer, Marshall isn鈥檛 ruling out the possibility that it happens occasionally. Biologists were also sceptical about Dayak stories about chevrotains, or mouse deer, swimming underwater and hiding with only their nostrils protruding to avoid predators, he says.聽Those . 鈥淧eople who spend a lot of time in the forest see really unusual things,鈥� says Marshall.
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