Insectivorous bats in anthropogenic landscapesSubmitted by editor on 25 May 2020.Get the paper!
Roeleke M, Blohm T, Hoffmeister U, Marggraf L, Schlägel UE, Teige T, Voigt CC
The common noctule bat hunts for insect swarms in the open air space across all kinds of different habitats. Yet, its ultrasonic radar for detecting insects only works over very short distances. Recently, our colleagues from the Tel Aviv University have shown that bats may hunt together in spread out groups to increase their chances for detecting food. To see whether such social foraging strategies may help common noctules to thrive even in landscapes under heavy impact from humans, we equipped common noctules with tiny GPS loggers and ultrasound microphones in two contrasting landscapes: woodland and agricultural land. Comparing their flight style and feeding activity captured by ultrasound, we found that only in the agricultural landscape, noctule bats eavesdropped on nearby conspecifics to find food. We believe that over the woodlands, insects were distributed evenly and thus easy to find for single bats. In contrast, clumps of insects might randomly drive across the large cropfields in the agricultural landscape, and finding them might become a gamble for a single bat. Therefore, it is good news that bats can cope with very different kinds of human modified landscapes by adjusting their foraging strategy to the prey distribution. However, our results also imply that in agricultural landscapes, bats depend on intact groups to hunt efficiently, and therefore rely on our willingness to protect them.
1) Researcher is pretty happy after finding another GPS / ultrasound logger within a crevice in a tree. The bat was using that crevice the day before as a temporary daytime roost and lost the device. Retrieval was aided by traditional VHF radio transmitters. 2) Typical scene of the agricultural landscape site in northern Germany.
3) By-catch that spend the day with the tagged noctule. Started to crawl around on the research assistant when released from the harp trap. Even wild Common noctule bats are quite relaxed when handled by humans.
Written by: Manuel Roeloke
Copyright all pictures: Manuel Roeleke