Meeting Abstract
Predators directly affect populations through mortality and indirectly through altered behavior and physiological stress response. Physiological and behavioral response may vary depending on whether the threat is perceived as an acute or a chronic stressor. Acute stress from predators can enhance reproductive success. In contrast, chronic exposure to predators can negatively affect reproductive success. Cortisol is the main stress hormone in fish and increases in response to predation threat and may facilitate antipredator behavioral response. We tested the hypothesis that chronic and acute predation threat would affect mating behavior of the livebearing mosquitofish, Gambusia affinis. We exposed mosquitofish (n=10-15/treatment) to Green sunfish, Lypomis cyanellus, a major predator for either 7 days or 30 min. We set up half of a tank with one male separated by a clear divider from two mature females (large and smaller).We placed the sunfish in the other half of the tank (clear divider) if the treatment was chronic exposure. On day 7, we placed the sunfish on the other half of the tank for the acute treatment for 15 min. In the presence of the predator, we removed the divider separating the male and females and recorded the number of mating attempts (gonopodial thrusts) towards each size of female for 15 min. We also examined mate choice using the same set-up but with no predator. Males thrusted significantly more towards the larger female over smaller females across all treatments. Interestingly males in the acute stress treatment, mated significantly more than males in the chronic or control treatments (which did not differ from each other). These results indicate that acute stressors increase mating behavior and that fish may have habituated to the threat of predators in the chronic treatment.
