Overland Movement and Activity of the Endangered White-Clawed Crayfish Austropotamobius Pallipe

Masefield, Stephanie (2018) Overland Movement and Activity of the Endangered White-Clawed Crayfish Austropotamobius Pallipe. Masters thesis, University of Gloucestershire.

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Abstract

The UK’s only native crayfish, the white-clawed crayfish Austropotamobius pallipes, is endangered and in decline across its range in Europe. The principle threat derives from the introduction, accidental and deliberate, of invasive crayfish species, which lead to losses of native crayfish through transmission of crayfish plague Aphanomyces astaci and competitive exclusion. Conservation programmes for white-clawed crayfish include captive breeding and conservation translocations. Crayfish are able to move terrestrially and this thesis examined the potential of white clawed crayfish to make terrestrial movements within an experimental arena. Results were compared with experiments on two UK invasive crayfish species, the signal crayfish Pacifastacus leniusculus and the red swamp crayfish Procambarus clarkii. White-clawed crayfish proved surprisingly willing to move onto a terrestrial environment, with 65% of animals tested making an exit from the water. Fewer signal crayfish and red swamp crayfish exited, but those that did, exited more frequently and spent longer in the terrestrial environment than white-clawed crayfish. An immediate and important outcome of these findings is to review captive enclosure design. Many more white-clawed crayfish made exits onto the terrestrial bridge when tested singly, than when in groups of four. This suggests a negative density-dependence in which crayfish are assessing habitat quality through the presence of conspecifics, or that when alone they make different behavioural decisions than when kept with conspecifics. White-clawed crayfish were tested in groups of four at varying sex ratios to investigate changes in activity level and interactions. Three metrics were captured: number of crayfish active in a group, how active the focal animal was, and number of interactions between the focal animal and its conspecifics. Size proved significant across the metrics, with larger animals showing less activity, taking part in fewer interactions, and a large size range corresponding to less activity in a group. This demonstrates the importance of using size in models of behaviour within crayfish, even when using size matched animals as seen here. Activity levels within the experimental tank corresponded with sex ratios. Having a higher percentage of males corresponded with more activity in the tank and female only trials were the least active groups. This is hypothesised to be due to the more agonistic nature of male crayfish and is despite the finding that overall males were slightly less active than females. Both sexes responded to the sex ratio of the system which consisted of four experimental tanks running through the same water system. Both sexes were more active when there were more males in the system. The finding that crayfish activity levels corresponded with sex ratios of animals they were only in aquatic contact with indicates they are responding to pheromones, which is relevant to aquarists and researchers alike. Overall this thesis found interesting differences in native and invasive species behaviours, and some thought-provoking intrinsic and extrinsic factors relating to activity levels.

Item Type: Thesis (Masters)
Additional Information: MSc by Research
Uncontrolled Keywords: White-Clawed Crayfish; Austropotamobius Pallipe
Subjects: Q Science > QL Zoology > QL360 Invertebrates
Divisions: Schools and Research Institutes > School of Natural & Social Sciences > Environmental Sciences
Depositing User: Susan Turner
Date Deposited: 24 Jul 2019 15:46
Last Modified: 24 Jul 2019 15:46
URI: http://eprints.glos.ac.uk/id/eprint/7059

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