Some bats eat fruit. Some eat insects, and a specialized few eat fish. Otonycteris hemprichii, the long-eared bats living in some of Israel’s harshest deserts, sup on scorpions, based on recent studies of their droppings.
That finding brought serendipitous added value to what had originally been a study of the desert-dwelling bats’ physiology by scientists at Ben-Gurion University of the Negev, in Be’er Sheva.
Once the insectivorous bats’ predilection for juicy scorpions had been discovered, on top of beetles and moths and the like, the researchers set out to ask and answer a number of other questions.
First, they tested the working assumption that the bats catch the venomous arthropods by the tail, to avoid their deadly stings. Observation proved that isn’t so, says Dr. Carmi Korine of the BGU Department of Desert Ecology. The bats don’t seem to try to catch the scorpions from any particular angle – and they do get stung.
That observation led to another working assumption, which has yet to be proven: that the long-eared bats are immune to scorpion venom. Alternatively, they could be incredibly macho about dealing with the agony of being stung, but that is less likely.
A second question that arose was whether the bats prefer a specific scorpion species (don’t we all) or if they are general feeders. Being large relative to insectivorous bats (if not compared with fruit bats), with some measuring around 7-8 centimeters from head to the base of the tail, and with the male weighing as much as 20 grams, generalized eating habits would presumably be helpful.
“We discovered they aren’t fussy,” says Korine. “They are generalists, eating a wide range of scorpions, including the deadliest of the lot in Israel – the yellow scorpion. They prey on those very happily.”
As desert bugs go, the scorpion is a meaty meal and having an appetite for them could be another way long-eared bats have adapted to the conditions of its desert habitats in the Negev, Judean Desert and other arid parts of North Africa, the Middle East and Asia.
The physiological studies conducted by Korine and BGU colleagues revealed several ways in which the bats had become metabolically adapted to the unforgiving desert climate – from the perspective of their physiological water economy and heat control.
The researchers also report, in a September 2014 paper written with scientists from Great Britain's Bristol University and published in the Journal of Experimental Biology, on the flexibility of the desert bats’ use of echolocation.
Some bat species have only one mode. However, this one can switch between the “whispering gleaning” mode that gets them ground-dwelling scorpions, and the “screaming” mode to catch insects on the wing. That duality in hunting mode could be a boon in the high-stress environment of the desert, where if it moves and you could eat it, you probably should.
Click here for story on students who invent a robot bat wing.
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