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Why do shore crabs not prefer the most profitable mussels?
Author(s) -
Smallegange Isabel M.,
Van Der Meer Jaap
Publication year - 2003
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1046/j.1365-2656.2003.00729.x
Subject(s) - carcinus maenas , predation , mussel , claw , biology , mytilus , fishery , optimal foraging theory , sex ratio , foraging , predator , decapoda , crustacean , zoology , ecology , population , demography , sociology
Summary We examined the link between handling time ( T h ), adopted feeding techniques, profitability curves and prey size selection to further understand the constraints that influence bivalve prey selection in shore crabs ( Carcinus maenas L.). Blue mussels ( Mytilus edulis L.) of different sizes were used as prey. Prey size was generalized to the ratio between mussel width and major chela length (MW : MCL) and prey profitability standardized to the ratio between prey mass eaten per unit breaking time and predator mass (1/h T b ). Crabs either crushed the mussel with their claws or opened the mussel using the more time‐consuming cutter technique. The latter technique was employed above a critical MW : MCL ratio (0·24). This threshold appeared to coincide with the ratio where prey profitability is maximal. When a range of prey sizes were offered simultaneously, an observed MW : MCL ratio (0·14–0·16) turned out to be lower than the predicted optimal MW : MCL ratio (0·16–0·22) and lower than the MW : MCL ratio where the first crab switched feeding techniques (0·16). Crabs preferred a MW : MCL ratio of 0·16 over the optimal ratio of 0·24 when given dichotomous choices between different MW : MCL ratios. Although larger and more profitable mussels can be crushed, we suggest that crabs select small crushable mussels to prevent claw wear and tear. Claw damage has a considerable effect on mating success and hence on an individual's fitness. Risk of claw damage may thus be of greater importance to a foraging shore crab than energy maximization.