A bush squirrel collected 500m from the fatal incident

The bizarre（奇异的） incident was witnessed by zoologist² Mr William Stanley, while he was conducting fieldwork in the forests of Tanzania.

"No-one has recorded this type of behaviour or incident before," says Mr Stanley, who saw the squirrel try to kill the bat in a tree above his head.

Rodents³ are not known to eat meat or hunt animals, so it is unclear why the squirrel would launch such an attack.

Mr Stanley, who works at the Field Museum of Natural History in Chicago, US has published details of the incident in the African Journal of Ecology.

For the past 20 years, he has studied small mammals in Tanzania, focusing on shrews（悍妇，泼妇）, bats and rodents（啮齿类）, usually conducting field work during July and August.

During one afternoon survey in the Mwofwomero Forest, in the Rubeho Mountains, he heard a fruit bat shrieking（尖叫，叫喊）.

"It was strange to hear an alarm call or vocalisation from a fruit bat typically we hear at night," he told BBC Earth News.

"That's what caught my attention. When I looked up I realised that there was a squirrel up in the branches where the noise was coming from. The next thing I saw was the flapping of the bat's wings."

Mortal wounds

Mr Stanley then describes how the events unfolded.

"It became apparent that there was an altercation⁴（争论，口角） happening between the squirrel and the bat, something I'd never seen before or ever heard of."

"The squirrel had the bat in its mouth, or it was at least biting it, and then the bat went quiet for a while and then starting flapping its wings again."

"The second time it started vocalising and flapping, the squirrel released it and the bat fell out of the tree and literally⁵ fell into these small saplings（树苗，小树） right above my head, and ultimately to my feet."

Mr Stanley recovered the now dead bat, a species known as Epomophorus wahlbergi, and photographed it.

"Both wings were broken at pretty much the same place on the same side and the side of the head was fractured（断裂的）," he explains.

Why the squirrel would want to kill the bat is a mystery.

Mr Stanley and his colleagues identified the squirrel as a Svynnerton's bush squirrel (Paraxerus vexillarius), which at a weight of around 280g is three times heavier than the 89g bat.

Like most other rodents, Svynnerton's bush squirrels eat vegetable matter, fruits, nuts and small insects. No squirrels are known to hunt vertebrates, or even scavenge（打扫，到处觅食） meat.

"The least likely hypothesis is that the squirrel was preparing to eat the bat," says Mr Stanley.

"The bat was injured and damaged in very specific places. This is pure speculation⁶, but it's almost as if the squirrel was seeking to maim⁷ the bat in some way. Maim it or kill it such that it couldn't fly."

"Either the squirrel thought the bat was a threat to it, or to its young if they were around, or to a food source. Maybe the squirrel was going after some fruit and the bat was hanging there and the squirrel wanted to get rid of some competition."

"Another possibility is that either the squirrel or the bat were mentally off balance."

"I don't think this is normal," he adds, suggesting that injury or disease could also have prompted the bizarre interaction.

Baboon⁸'s taste for bat

In the African Journal of Ecology research paper, Mr Stanley and colleague Ms Leah Collett, who works at the Animal Behaviour Research Unit based in Mikumi, Tanzania, describe another rare incidence of bat predation（掠夺行为）.

Conducting field work in the Mikumi National Park, Ms Collett witnessed a yellow baboon（狒狒） eating another fruit bat of the same genus (Epomophorus minor).

While baboons⁹ are known to eat reptiles¹⁰（爬行动物）, birds and some mammals such as hares, they have never before been recorded eating bats.

"What was really intriguing¹¹ about this, which may be pure coincidence or not, is that both the bat and the baboon that ate it were pregnant," says Mr Stanley.

"We found a very developed foetus（胎儿） from the bat, and the baboon gave birth five days after the event was witnessed. Whether there was a connection or not we can't say."