Male toads change their aggregation behaviour when hybridization is favoured.

In many species, males form aggregations in which they compete for access to mates. Such aggregations can consist of multiple species, such that hybridization or reproductive interference between species becomes a risk. To enhance mating success with conspecifics, males might preferentially aggregate with conspecifics to minimize the risks of mating or competing with heterospecifics, especially if females are attracted to groups of conspecific males or avoid heterospecific males. Here, we used spadefoot toads (genus Spea) to evaluate whether males respond to the same environmental cue that females use to facultatively alter their mate choice decisions for conspecific versus heterospecific males. We took advantage of a system in which females facultatively prefer to mate with heterospecifics when doing so is adaptive. We found that males preferentially aggregate with conspecific males when hybridization is disfavoured for females (so that females prefer conspecifics); however, males show no such preference for aggregating with conspecifics when hybridization is favoured (and females are more likely to prefer heterospecifics). We did not find this pattern in a different spadefoot species where females do not adaptively hybridize; males preferentially aggregated with conspecifics in one environment and did not alter their behaviour when the environmental cue was changed. Our results therefore suggest that males track the same environmental cues that females use during mate choice. These findings highlight the potential for males to facultatively adjust their behaviour in response to competitors, as well as the role that male–male interactions might play in the likelihood and consequences of hybridization between species. • Males aggregate with conspecifics when hybridization is disfavoured. • When hybridization is favoured, males spend less time with conspecifics. • This context-dependent behaviour mirrors female mate choice. • We found no such behaviour in a congeneric species lacking adaptive hybridization. [ABSTRACT FROM AUTHOR]