1 Department of Biology, Concordia University, 7141 Sherbrooke St. West, Montreal, QC, H4B 1R6, Canada.
2 Department of Biology, Missouri State University, 901 South National Ave., Springfield, MO, 65897, USA.
3 Department of Life Sciences, University of the West Indies, St. Augustine, Trinidad and Tobago.
4 School of Mathematical and Natural Sciences, University of Arkansas at Monticello, 346 University Dr., Monticello, Arkansas, 71656, USA.
5 Department of Biology, Concordia University, 7141 Sherbrooke St. West, Montreal, QC, H4B 1R6, Canada. Electronic address: grant.brown@concordia.ca.

Males and females, especially in species with more pronounced sexual dimorphisms, may face very different trade-offs between detecting and avoiding predation threats and the need to court potential mates. Within aquatic ecosystems, the use of reliable publicly available chemosensory risk assessment cues allows prey to assess local threats and optimize these behavioural decisions. Recent studies suggest in species with more pronounced sexually dimorphisms, males may show reduced responses to acute predation cues due to the potentially high costs of lost mating opportunities. However, in species that are less sexually dimorphic, males and females might be expected to respond to acute predation cues in a similar fashion. Here, we conducted laboratory trials to test the effects of sex and size (as a proxy for reproductive state) on the response to acute predation cues in wild caught Hart's rivulus (Anablepsoides hartii), a species with relatively low levels of sexual dimorphism. We quantified the antipredator response of reproductive and non-reproductive males (n = 50) and females (n = 49). Focal individuals were exposed to conspecific alarm cues (AC), conspecific disturbance cues (DC), or a water control (W). We found sex differences in baseline activity (before introduction of cues); females spent more time under shelter compared to similar sized males. Despite these differences, we found that male and female rivulus exhibited similar responses to acute risk cues regardless of size. Our results are consistent with the hypothesis that in the absence of strong sexual dimorphisms, male and female rivulus maybe subject to similar behavioural trade-offs in response to predation threats.