Crayfish article 2

Crayfish article 2 - Activity patterns, behavioural...

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Unformatted text preview: Activity patterns, behavioural repertoires, and agonistic interactions of crayfish: A non-manipulative field study Karen M. Davis & Robert Huber 1) (Department of Biological Sciences and J.P. Scott Center for Neuroscience, Mind & Behavior, Bowling Green State University, Life Sciences Building, Bowling Green, OH 43403, USA) (Accepted: 16 January 2007) Summary Agonistic behaviour of crayfish has been studied extensively in laboratory settings where pairs or groups of individuals are allowed to interact within an experimental arena. Crayfish agonistic behaviour within its natural context, however, has received little attention to date. The present, non-manipulative field study explored activity patterns, behavioural repertoires, and agonistic encounters of rusty crayfish ( Orconectes rusticus ) during the summer months using continuous, 24-hour, underwater video recording at a series of representative field sites. Following the filming, crayfish within the vicinity of the camera site were captured and mea- sured. Individual densities were high, reaching a maximum of 68 individuals/m 2 at some sites. Large crayfish predominantly inhabited deeper sections of the river and were mostly active at night, whereas small crayfish generally utilized the shallows and were active outside their burrows during day and dusk. Time outside their shelter was mainly used for feeding. Individuals frequently returned to the same shelter they had emerged from. Agonistic en- counters were common events and generally occurred in the context of shelter acquisition or defense. Dyadic fighting progressed with escalating sequences of stereotyped aggressive acts. Furthermore, high intensities with unrestrained use of claws were seen in encounters between size-matched opponents. The results of this study allow us to root laboratory find- ings of crayfish aggression within a comprehensive, ethological framework and to consider ultimate consequences for individual fighting decisions and strategies. Keywords : agonistic behaviour, activity patterns, crayfish, ethology, shelter defense. 1) Corresponding author’s e-mail address:[email protected] © Koninklijke Brill NV, Leiden, 2007 Behaviour 144, 229-247 Also available online - www.brill.nl/beh 230 Davis & Huber Introduction Decapod crustaceans are the prevalent scavengers of temperate, aquatic en- vironments. Crayfish and many of their phylogenetic kin occur in high num- bers, dominate invertebrate biomass, and play an integral role in the structur- ing of many aquatic communities (Cooper & Uzmann, 1980; Miller, 1985; Momot, 1995). Populations of crayfish in Lake Ontario, for instance, reach densities of up to 20 individuals/m 2 , and their presence profoundly impacts local ecology and food webs (Stewart & Haynes, 1994). Despite their eco- logical importance, little is known about the natural behaviour of this group in the field. Behavioural observations are complicated by largely nocturnal habits, frequent use of shelters, and their alertness towards the presence of...
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Crayfish article 2 - Activity patterns, behavioural...

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