Behavior of the Oregon Mud Crab, Hemigrapsus Oregonensis (Dana) (Brachyura, Grapsidae)

Abstract

Among the crustaceans studied, the behavior of true crabs is the most varied and complex. The variety of behavior exhibited in brachyuran families was briefly described by Sch?ne (1968), while Stevcic (1971) attributed such diversity and complexity to centralization of the nervous system during brachyuran evolution. Unfortunately, relatively few behavioral accounts exist for brachyurans despite the abundance of crab species and the opportunity for comparative studies of their behavior and ecology. The genus Uca of family Ocypodidae has received the most ethological attention. Crane's (1975) comprehensive study of genus Uca provided comparisons of behavior, ecology and morphology among species of fiddler crabs, and focused primarily on the major chela and its use during courtship and aggression. Acoustic communication by fiddler crabs was investigated by Salmon (1965, 1967) and Salmon & Atsaides (1968, 1969). Numerous other investigations provide evidence for the behavioral complexity found in the genus Uca; e.g., Langdon (unpubl.) studied shape discrimination and learning by Uca pugilat or (Bosc), and Zucker (1974) reported that males of Uca terpsichores Crane build shelters over burrow entrances to reduce territorial aggression during peak courtship periods. Behavioral reports for ocypodid crabs outside genus Uca, however, are scarce (Hughes, 1966; Linsenmair, 1967; Griffin, 1968). Except for the more recent studies of fiddler crabs, quantitative investigations of behavioral organization and causal relationships have been reported for only one species of aquatic crab from each of the families Potamidae, Majidae and Por tunidae. Vannini & Sardini (1971) examined aggression and the linear dominance hierarchies established by Potamon fluviatile (Herbst) (family Potamidae). Para meters of agonistic behavior (e.g., stereotypy, releasing postures, and the effects of size, sex, etc.) for the spider crab Microphrys bicornutus (Latreille) (family Maji dae) were quantified by Hazlett (1972a, b) and Hazlett & Estabrook (1974). Jachowski (1974) quantified the performance of agonistic action patterns for the blue crab, Callinectes sapidus Rathbun (family Portunidae), during intraspecific encounters and model presentation experiments. Such quantification is needed for accurate assignment of functions to action patterns. Publication of complete and