Acoustic and Flight Behaviour of Emerging Greater Horseshoe Bats in Paired Flight

Abstract

Emergence can be particularly complicated for bats as they orientate in an environment with a higher chance of possibly jamming due to conspecifics. Yet jamming avoidance in bats is understudied in emergence, especially in high duty cycle bats. Here I examined the high duty cycle bat Rhinolophus ferrumequinum for evidence of jamming avoidance responses while emerging.
Bats were recorded from a field site in Wales via acoustic tracking. Solo and paired individuals were identified and subsequently analysed for flight and acoustic jamming avoidance behaviours. I concluded that while the paths of paired flights were statistically different there was not enough evidence to truly suggest that paired flight paths were different from solo flight paths. The bat experience for each paired bat was calculated, allowing for the investigation of differences in the frequency and the timing of the calls. Here, I present the first indications of the intentional alternation of calls in a high duty cycle bat, a jamming avoidance strategy in use by low duty cycle bats, and the use of a synchronization strategy as well. In frequency, pairs were found to be expanding the bandwidth of the terminal FM sweep, confirming other reports. However, I concluded that this was not a clutter response, as previously suggested. Some pairs were found to be separating their echo frequencies more than expected but more interestingly one pair was found to have frequencies closer than expected. Considering that this pair was also synchronising calls it would appear that this pair was was intentionally jamming one another. I suggest that this is actually a jamming avoidance response in which echoes are matched so that there is no jamming, termed ‘allo-echoic interception.’ This study provides some evidence for the possibility of acoustic jamming avoidance responses in high-duty cycle bats during emergence, both theorized and novel.

Date of Award	2 Dec 2021
Original language	English
Awarding Institution	University of Bristol
Supervisor	Marc W Holderied (Supervisor)