MEPS 522:181-192 (2015)  -  DOI: https://doi.org/10.3354/meps11160

ABSTRACT: Invasive consumers often achieve very high abundances and consequently have large consumptive impacts on invaded habitats. Consumptive impacts that strongly reduce the abundance of native prey cause invasive species to subsequently make less favorable prey choices. Here we examine the energetic implications of diet choice in the invasive Asian shore crab Hemigrapsus sanguineus, an omnivorous consumer that has strongly reduced its favored prey species across much of its invaded range. In the first of 2 long-term feeding experiments, we examined the energetic implications of animal versus algal consumption when this invader has the choice between its most commonly consumed foods. In the second experiment we compare the energetic payoff of consuming several alternative algal and animal foods that are available on beaches where this invader has already strongly depressed or depleted its preferred prey items. We show that despite the primarily herbivorous nature of the Asian shore crab, animal consumption yields the greatest energetic payoff. We also demonstrate that on beaches where its preferred foods have been depleted, cannibalism presents the best choice energetically. However, in a third experiment we demonstrate that the propensity for cannibalism in this species is weak. Our results may help explain recently described declines in Asian shore crabs on beaches where it has dominated for ~20 yr since its invasion. Further, extension of our results provides a general hypothesized framework to understand self-limitation of invasive species in habitats that they have strongly altered.

KEY WORDS: Cannibalism · Energetics · Invasive species · Self-regulation