CONFLICTING DEMANDS IN SAND GOBIES - PREDATORS INFLUENCE REPRODUCTIVE-BEHAVIOR

The effects of predation risk on the reproductive behaviour of male an d female sand gobies, Pomatoschistus minutus, were investigated in two separate aquarium studies. In the presence of a predator (cod, Gadus morhua), males decreased their courtship activity while females did no t alter their level of activity. In the second study, there was no dif ference between treatments (with and without predator) in the time fro m when a female was presented to a male with a nest until spawning too k place or in the amount of eggs laid. However, prespawning behaviour differed between the two treatments. When the cod was in sight, both m ales and females burrowed in the sand more often. In the absence of a predator, pairs spent longer together in the nest before spawning star ted, and females also inspected the nest alone, which never happened d uring predator presence. Hence, both sexes make trade-offs between pre dator avoidance and behaviours associated with mating. Females, howeve r, seem to take higher risks during the courtship phase in order to fi nd a partner compared to males.