Lek breeding in the lesser short-tailed bat (Mystacina tuberculata): male courtship, female selection, and the determinants of reproductive strategies

Abstract

Bats (Mammalia: Chiroptera) are one of the most successful mammalian groups on Earth, and likely display the widest range of mating systems of all mammals. Despite this variety, one mating system appears to be underrepresented: lek breeding. Leks are characterised by aggregations of sexually-displaying males that are visited by receptive females for the sole purpose of fertilisation. To date only one bat species has been confirmed to breed using leks. In this study I investigate the possibility of lek breeding in a second bat species, the lesser shorttailed bat (Mystacina tuberculata) of New Zealand, using a variety of field and laboratory methods. Males in this species use “singing roosts” to sing during the breeding season, presumably to attract females. Through the use of radiotelemetry I show that females have large home ranges and dynamic roosting patterns. Through the use of video footage, spatial analyses, and passive-integrated transponder tags I confirm lek breeding in M. tuberculata; male singing roosts are aggregated spatially, are defended by males, and are visited by females for mating purposes. I also demonstrate that male singing roosts are aggregated around communal roosts used by the population, likely in response to the consistent high female densities in these areas. I analyse the characteristics of male songs and show that smaller males have higher song outputs than larger males. Furthermore, through the use of genetic analyses I show that smaller males have higher reproductive success than larger males, likely due to females selecting males with higher song outputs. Small size may permit males to expend less energy during their nightly activities, and thus they can expend more on courtship. Throughout the study I present many unique behaviours not described previously, including an alternative male strategy known as “timesharing” – multiple males sharing singing roosts. My results represent a useful description of sexual selection in a bat, as details of mating behaviour are known for only a fraction of bat species. I use my results to suggest conservation strategies for M. tuberculata, as well as to reexamine the apparent rarity of the mating system within the Order.