Prey can detect their predators through different forms of chemical information try to reduce the predation risk. Predators can kill the prey directly (direct effect) or affect them through their mere presence/predation risk (risk effects). Predation risk affects many aspects of prey´s life such as morphology, behavior, life history etc. Prey need to develop defenses or modify behavioral traits to reduce the predation risk. Littorina littorea also can induce some anti-predator responses to reduce the predation risk from shore crab Carcinus maenas. Until now most of the research focused on shell mass and avoidance behavior of snails and found increasing of shell mass and avoidance behavior in presence of predatory crabs. This research focused on not only the risk effects of predatory crabs on shell mass and avoidance behavior but also on feeding, mating and egg production capability of littorinid snails. Not only the continuous 24 hours risk effects on behavioral trait changes of snails but also the effects of temporal variation in risk (frequent and infrequent risk, that is very common in nature) were also examined. Very few research has been focused on this issue until now.