Sex recognition of female-like sneaker males in the Comanche Springs pupfish, Cyprinodon elegans

In mating systems with alternative reproductive tactics, female mimicry may allow some males to avoid aggression from larger territorial males and garner matings. However, selection is predicted to favour the territorial malesʹ ability to discriminate against female mimics as they may usurp fertilizations in a maleʹs territory and potentially eat eggs fertilized by the territory owner. I tested whether territorial males were able to recognize female-like sneaker males in the natural population of Comanche Springs pupfish, Cyprinodon elegans. Results of a field study conducted at Balmorhea State Park, Balmorhea, TX, U.S.A., revealed that territorial males behaviourally discriminate size and sex of conspecifics. They were more aggressive to large males than to sneaker males. However, territorial males also directed more aggressive behaviours towards sneaker males than similarly sized females. As sneaker males garner little aggression when a large male intruder is also present, they will potentially gain opportunities to spawn if large males commonly intrude into malesʹ territories. These results suggest that aggression towards sneaker males is context dependent and that the social environment may have important evolutionary fitness consequences for both territorial males and sneaker males.