Sex and background risk influence responses to acute predation risk in Trinidadian guppies

Intraspecific sex differences in morphology, physiology, and behavior are widespread among taxa. However, despite their fundamental importance, they have been relatively understudied in the context of risk assessment. For instance, with Trinidadian guppies (Poecilia reticulata), there has been a bias toward the exclusive use of females, as males are thought to be less responsive to acute predation threats. However, there is little empirical evidence supporting this assumption. Moreover, the antipredator behavior of male guppies has been unexplored, perhaps resulting in the over-generalization of female behavior to both sexes in previous studies. Here, we conducted laboratory experiments involving wild-caught and laboratory-reared guppies. In Experiment 1, shoals of either male or female guppies from a high-predation population were tested for their response to alarm cues, novel odor, or a water control. We found that while female shoals exhibited strong antipredator responses to alarm cues and neophobic responses to novel odor, male shoals exhibited only a weak response to alarm cues and no evidence of neophobia. In Experiment 2, we exposed male and female guppies to high- or low-predation risk and then tested individuals for their responses to alarm cues, novel odor, or water control. Regardless of background risk, males did not respond to any stimulus. In contrast, low-risk females exhibited antipredator responses toward alarm cues and those from high background risk displayed neophobia. Our results suggest that females are more cautious when encountering an acute predation risk, highlighting the importance of accounting for both sexes in studies on predation.