Sexually attractive traits predict predation-threat sensitivity of male alternative mating tactics

Although visual sexual signals, such as ornamental colors and courtship displays, and large body size in males are attractive to females in numerous species, they may also inadvertently attract the attention of eavesdropping predators and thus may be costly in terms of increasing individual risk of mortality to predation. Theoretically, more color ornamented and larger males should be more predation threat sensitive and suppress their sexual signaling and(or) mating effort relatively more than their less color ornamented and smaller counterparts when under predation hazard. Here, we experimentally tested this hypothesis by quantifying concurrently the rates of alternative mating tactics (courtship displays, sneak mating attempts) expressed by male Trinidadian guppies (Poecilia reticulata) varying in color ornamentation and body size under a staged immediate threat of predation. Males suppressed their overall mating effort in response to the perceived predation threat, decreasing the frequency of their (presumably more conspicuous) courtship displays significantly more on average than the frequency of their sneak mating behavior. Statistically controlling for body length, more color-ornamented males were more threat sensitive in their courtship displays, but not sneak mating attempts, under predation hazard than drabber males. Controlling for body coloration, larger males exhibited lower courtship and sneak mating efforts than smaller males in both predation treatments, but body length only influenced threat sensitivity in sneak mating behavior. These results are consistent with both the threat sensitive hypothesis and asset protection principle and highlight the phenotype dependency and adaptive plasticity of alternative mating tactics in male guppies under varying predation risk. Males who bear sexually selected signals or ornaments and are large bodied might attract eavesdropping predators. Theoretically, they should be more predationthreat sensitive and accordingly suppress their mating effort relatively more than their less ornamented and smaller counterparts when under predation hazard. We show that more color-ornamented male guppies are more threat sensitive in their courtship displays than drabber males when threatened, whereas male body length predicts threat sensitivity in coercive (sneak) mating attempts.

Automated summary

In the face of predation threat, male guppies adjust their mating tactics by reducing courtship displays, especially those with more color ornamentation. Larger males exhibit lower courtship displays and sneak mating efforts compared to smaller males. The results support the threat sensitive hypothesis and asset protection principle, demonstrating the adaptive plasticity of male guppies' mating tactics under varying predation risk.