Decision making and risk in Strongylocentrotus droebachiensis in competitive and non-competitive foraging environments

Abstract Foraging behavior is known to have drastic impacts across the animal kingdom, from the behavior of vertebrates as well as invertebrates. Green sea urchins (Strongylocentrotus droebachiensis) are well known omnivorous echinoderms that display a wide diversity of behavioral responses to chemical and tactile stimuli. Green sea urchins likely consider the stimuli of conspecific presence especially in foraging environments where competition can be high. The foraging behavior, specifically ability to reach a food item, of urchins was examined in four distinct trials with urchins under competitive and non-competitive environments with conspecifics after determining the preferred animal protein. Two trials examined the effect of cover type, and the other two considered urchins with no available cover in different water flow regimes. Overall, urchins competing with conspecifics were faster to reach food than those that were alone. However, when cover was available, non-competitive urchins most often did not reach the food item in the time allotted. Urchins likely weigh the risk and benefits of moving towards high value food with the competitive environment and cover type. These results indicate the importance of considering the conspecific environment in urchin behavioral studies and can have implications for aquaculture.