Cer­tain sur­faces foil bat echolo­ca­tion

Honolulu Star-Advertiser - - NEWS -

Bat echolo­ca­tion is a finely tuned sense. By emit­ting high-fre­quency calls and lis­ten­ing for re­turn­ing echoes, bats can deftly nav­i­gate com­plex sur­round­ings and pre­cisely tar­get mov­ing prey in the dark. But this ex­tra­or­di­nary ca­pa­bil­ity is not fool­proof. A study pub­lished Thurs­day in Sci­ence re­veals a weak spot in bat echolo­ca­tion: smooth, ver­ti­cal sur­faces such as the metal or glass plates on build­ings can trick a bat into think­ing it is fly­ing in open air.

The find­ings might help ex­plain why the crea­tures are of­ten found dead or in­jured near build­ings and other smooth struc­tures, said Ste­fan Greif, an au­thor of the study and a post­doc­toral re­searcher af­fil­i­ated with the Max Planck In­sti­tute for Or­nithol­ogy in Ger­many and Tel Aviv Univer­sity in Is­rael.

When a bat ap­proaches a smooth, ver­ti­cal sur­face from an an­gle — as it would when turn­ing a cor­ner in a rec­tan­gu­lar tun­nel — its echo-lo­cat­ing calls mostly re­flect away from it. It’s not un­til a bat gets very close to a flat, ver­ti­cal sur­face that some of its calls end up hit­ting the plate at a 90-de­gree an­gle and bounc­ing right back.

At this point, Greif and his col­lab­o­ra­tors noted, bats tended to change their echolo­ca­tion pat­terns, short­en­ing the time be­tween calls, to col­lect more in­for­ma­tion. But it was of­ten too late — out of 78 in­stances they ob­served of bats com­ing close to a ver­ti­cal plate, 25 re­sulted in near misses while 53 re­sulted in crashes.

STE­FAN GREIF / NEW YORK TIMES

Echolo­ca­tion does not pre­vent bats from fly­ing into smooth, ver­ti­cal sur­faces. Above, a greater mouse-eared bat.

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