Learning of predatory skills by shore-crabs Carcinus maenas feeding on mussels and dogwhelks

Abstract

Carcinus maenas (L.) used 5 recognizable methods to attack mussels and 3 methods attack dogwhelks. The frequency of usage varied among methods but did not change as crabs experience of the prey. The mean number of attacks required to open prey decreased with practice, irrespective of the methods used. The mean time to break open a prey decreased by a factor of 0.30 for mussels and about 0.28 for dogwhelks after 5 to 6 prey had been eaten. Reductions in breaking time were both less marked and slower when mussels and dogwhelks were presented alternately crabs. Mean breaking times for the first prey offered In trials separated by over 4 d were similar to associated with naive crabs, but were shorter in trials separated by smaller time intervals. Skills therefore gained within 1 to 2 h but were lost at a much slower rate. Crabs have a learning capacity can cause prey items to become transposed in rank and which could lead to switching appropriate circumstances. Alternate handling of dissimilar prey reduces learning efficiency and increase the disparity in abundances of alternative prey necessary for switching to occur.