An exciting new tool called iBatsID is set to revolutionise bat identification for conservation efforts throughout Europe, with the ability to classify the calls of 34 species found across the continent. The developers assessed 1350 recordings from the echolocation call library EchoBank, recording the values of 24 different call features from each species. Of the features studied, 12 were identified as being most useful for distinguishing the difference between species, including minimum and maximum frequencies and call duration. With an average species-level classification accuracy of 83.7%, the tool can successfully identify the majority of European bats to species level, with the exception of some members of the Myotis genus that have extremely similar calls and can accurately be classified to subgroup level. iBatsID is freely available for use and will allow standardised acoustic identification for bat research across Europe, the consistency of which will improve the validity of continent-wide monitoring.
Ref: Walters C. L. et al., 2012. A continental-scale tool for acoustic identification of European bats. Journal of Applied Ecology [link]
The preferred prey of the Natterer’s bat (Myotis nattereri) are flies (Diptera) of the suborder Brachycera, or diurnal flies. Bats hunt at night, and those that are insectivorous or carnivorous must rely on their sense of echolocation in order to find their prey. The difficulty lies in that flies sitting on a substrate such as a leaf or a wall are almost impossible to detect using echolocation. How it is that the Natterer’s bat manages to locate its prey was investigated by studying bats hunting houseflies (Musca domestica) in the setting of a cowshed. The bats seemed unable to locate individual flies sitting on the ceiling, even if the flies were on the move. But interestingly, the chance of being attacked by a bat increased hugely once flies began mating. During copulation, the male fly buzzes its wings, producing click-like noises. The bats appear to ‘eavesdrop’ on these sounds and use them to locate their prey. There is an extra bonus for the bat in listening out for this behaviour - in locating a copulating pair, they get a meal of not one, but two flies in a single attack. Confirmation that the bats were responding to acoustic signals from copulation was given when speakers were installed in the cowshed that played these sounds, resulting in attempted attacks and investigation by the Natterer’s bats. In contrast, they did not respond to lower frequency tones typical of a moving fly, suggesting that they attend specifically to the sounds of flies in copulation. Though this was tested in a cowshed setting, it is likely that this method is also used by bats when searching for their prey in vegetation and other settings.
Ref: Siemers M. B. et al. (2012) Bats eavesdrop on the sound of copulating flies. Current Biology 22(14) [link]