MEPS 540:135-144 (2015)  -  DOI: https://doi.org/10.3354/meps11491

ABSTRACT: In intertidal communities, abiotic factors like wave exposure can directly and indirectly affect an organism’s morphology, foraging behavior, available prey, prey choice, and predators. Although these factors may be transient, their influences persist to affect optimal foraging decisions of intermediate consumers and any accompanying behaviorally mediated trophic cascades. In this study, we documented the influence of wave action on prey available to the whelk Nucella lapillus at wave-exposed and wave-protected sites in the Gulf of Maine. We then determined if whelks from wave-exposed and wave-protected sites similarly reduced foraging in response to cues from the predatory invasive crab Carcinus maenas and if crab cues altered the whelks’ preference for barnacles Semibalanus balanoides over mussels Mytilus edulis. We found that while mussels were more abundant at wave-exposed sites than at wave-protected sites, whelks from both habitats consistently preferred barnacles and did not switch prey in the presence of crab cues. Furthermore, the influence of crab cues on the whelks’ foraging was not detected in the consumption of the less preferred prey (mussels), and in the consumption of barnacles, it was only consistently observed in whelks taken from wave-protected sites. We suggest that the whelks’ preference for barnacles over mussels demonstrates an optimal foraging decision in which the whelks are maximizing energetic gain by choosing the less energetically demanding prey. While local populations of whelks may express different behavioral responses to predators due to abiotic conditions, our results suggest that the preference of N. lapillus for barnacles is not altered by predator cues, wave exposure, or prior diet.

KEY WORDS: Nucella lapillus · Carcinus maenas · Mussel · Barnacle · Wave exposure · Predation risk · Prey choice · Indirect interaction