News — Boise State University postdoctoral research associate Cory Toth co-authored an article titled “Courtship behaviour and display-site sharing appears conditional on body size in a lekking bat.” The study explores the complex rules governing sexual selection in the largely undescribed lekking bat species, the lesser short-tailed bat of New Zealand. During the breeding season, male short-tailed bats sing like birds from small cracks in trees to attract females. Although lekking males are normally territorial creatures during mating season, in their study, researchers observed that some males were incentivized to form “timeshare” singing roosts to attract females, while others continued to sing alone. Timeshare roosts were ‘shared’ between the same (between two to five) males each night, each one entering the roost after the other had left to continue singing. These relationships appear to last for years.
Furthermore, the study found no fitness differences between the timeshare and solitary males. However, solitary males were significantly smaller than timeshare males and had both higher song outputs and higher roost occupancy rates. Meanwhile, timeshare roosts had higher overall occupancy rates.
The authors suggest that smaller males may have higher energy reserves than larger males, potentially gained through greater flying efficiency. While the authors assumed that kin selection may explain timeshare formation, only one timeshare roost consisted of males that were closely related (potentially half-brothers), while the others consisted of completely unrelated individuals. The observed discrepancy in size and behavior between the males of the two roost types suggests that solitary and timeshare singing represent separate strategies – specifically, that potential by-product mutualisms may promote timeshare formation among some males. If this is the case, it would represent the first cooperative breeding display described in mammals, and the first cooperative display conditional on body size. While future work is required to confirm that timesharing represents true cooperation, this is one of the first descriptions of the courtship behavior of the world’s only known lek-breeding bats, and important information for the conservation of a unique, threatened species.
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