Predatory risk increased due to egg-brooding inArmadillidium vulgare(Isopoda: Oniscidea)

Cost of reproduction is associated with a reduction in subsequent survival or future breeding success. A decrease in survival rate of parents during or after reproduction reduces the probability of their future reproduction. However, few studies have demonstrated such survival costs to parents. Females of Armadillidium vulgare hold their eggs in a marsupium and brood these until the young hatch. Caring for eggs in a marsupium seems to place a large burden on brooding females, and it restricts their predator avoidance behaviour. As such, costs of care may increase the mortality rates of brooding females. To reveal the costs of parental care, we examined the effects of egg brooding on behaviour and predation risk. Egg-brooding females decreased speed of locomotion and rolling duration, and were killed by predators at a higher rate. Our results indicate that egg brooding in A. vulgare has costs in the form of predation risk.