The mangrove tree crab has been reported in some literature as an herbivore (de Lacerda 1981, Warner 1967), although it is more likely an opportunistic omnivore (Díaz & Cuesta 1989) in many instances. Observations in the field and examinations of gut contents have determined that A. pisonii consumes a variety of plant and animal tissue. Plant matter found in the guts of adult crabs consists of: several species of macroalgae; seagrasses including shoal grass, Halodule beaudettei and turtle grass, Thalassia testudinum; and the leaves of the white mangrove, L. racemosa, the red mangrove, R. mangle and the black mangrove A. germinans. Of these, R. mangle was the most abundant food, comprising approximately 84% of gut contents (Erickson et al. 2003). Crabs feed on living mangrove leaf tissue, leaving behind distinctive scraping marks (Beever et al. 1979, Erickson et al. 2003, Feller 1995). Even in areas of low crab abundance, this behavior can account for up to 96% of the herbivory in the mangrove forests (Feller & Chamberlain 2007), focused mainly on the older leaves in fringing zones (Erickson et al. 2003, Feller & Chamberlain 2007). In addition to plant material, crab guts have included animal matter such as nematodes, crustacean appendages, fish scales, foraminiferans and polychaetes (Erickson et al. 2003). The larvae of A. pisonii appear to be somewhat omnivorous as well. The majority of the diet in larvae studied consisted of diatoms, mangrove detritus, tintinnids and copepods were also consumed (Schwamborn et al. 2006). Predators: As with most organisms that reproduce via planktonic larvae, the mortality of A. pisonii is high. On average, it is estimated that only 0.04% of larvae live to become newly settled juveniles. Of those, about 17% reach an adult size of 1.8 cm (Warner 1967). One reason for mass mortality is the high level of predation. While in the water column, the larvae of A. pisonii may be preyed upon by a variety of other zooplankton, small fishes and benthic filter feeders like barnacles, hydroids and anemones. Once the mangrove tree crab reaches adulthood, it has the potential to be preyed upon by birds, mammals and larger crabs such as Goniopsis cruentata (Warner 1967). However, terrestrial predator avoidance in this species appears to be highly developed. Adults have the ability to cling tightly to tree branches and bark, may reach climbing speeds of 1 m/s and have the ability to leap from tree canopies onto mud banks or into the water below (Warner 1977). This jumping behavior may occasionally prove fatal as fishes can also consume A. pisonii when the crabs leap into the water (Díaz & Conde 1989). Social Behavior & Territoriality: Like many decapod crustaceans, mangrove tree crabs have developed social behaviors and territoriality. Females are most always subordinate, relegating physical disputes to the males in the population. Males have larger, more developed chelae, or claws, which they use to push each other during aggressive encounters concerning territory or mate choice (Warner 1970). Once a home range has been established, individuals may inhabit the same area for periods of several weeks to months (Warner 1970).
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