Bats are unique among mammals thanks to their ability to fly, but what goes up must come back down. An analysis of bats鈥� landing methods has revealed that their touchdown techniques can give insights into other aspects of their lifestyle, such as the kind of shelter they live in.
鈥淚f you鈥檙e going to be able to fly, you have to be able to land without dying,鈥� says at the American Museum of Natural History in New York City.
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Pulling off a safe landing is tied directly to a critical resource: the roosts where bats seek shelter and raise their young. Roosts provide protection and a social life, and act as an anchor for how bats interact with their surrounding environment.
While at Brown University in Rhode Island, Boerma and his colleague , also at Brown University, investigated the mechanics of bat landings by recording footage of 665 landings from 35 species of bats, mostly at field sites in Central America, Bulgaria and China. They then compared the bats鈥� landing techniques with the properties of their roosts and the evolutionary relationships between the species.
The pair found that a bat鈥檚 landing style was related to the physical properties of the landing surface, rather than the roost鈥檚 location. Boerma was surprised, as he originally expected that bat species that were closely related or had around the same body size would land similarly regardless of their roost characteristics.
Some bats landed with a flip as they grasped the surface with their feet. This approach seems to have evolved multiple times and is linked to stiff, horizontal roosts, like cave ceilings. Four-point landings, in which the bat touches down with all four feet at once, are the simplest and oldest method, derived from the grappling descent of gliding ancestors, and were common with surfaces like foliage that have a bit more give. Some three-point landings worked well in cramped situations.
The association between three- or four-point landings and roosts made from foliage makes sense, says at the University of California, Merced, as distributing force across several feet may 鈥渋ncrease the likelihood of finding purchase鈥� on contact with the surface.
Changes in landing style may have had a role in bats鈥� evolution and diversification, opening up opportunities in new habitats, say Boerma and Swartz. The importance of landing style could also have implications for bat conservation. 鈥淚f a species鈥� landing mechanics are highly specialised for a particular roosting ecology, then it may not be able to adapt to new roosts following deforestation,鈥� says Boerma.
Future work will involve looking at the bats鈥� limb bones to see if certain skeletal features are involved with specific landing acrobatics, he says.
Reference: BioRxiv, DOI: 10.1101/2021.10.21.465259
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