Optimal and Anti-Predator Foraging in the Sand Bubbler Crab Scopimera inflata (Decapoda: Ocypodidae)

Abstract

Sand bubbler crabs Scopimera inflata are central place foragers that spend long periods feeding on nutritionally poor surface sediment adjacent to their burrows. Individuals make series of excursions from their burrows usually moving progressively in clockwise or anticlockwise directions so that they feed on areas of ‘‘virgin’’ sediment on successive forages. However, they foraged further from the burrow than was predicted by a model of central place foraging. Foraging crabs were under intense predation pressure from the redcapped plovers Charadrius ruficapillus in the study area. Success rates of plovers in capturing crabs were high. Crabs can escape attacks by retreating back into their burrows but normally waited for less than a minute before recommencing to forage. This may be sufficient to escape a second plover attack because plover waiting times at burrows were only about 10 s in duration.