Flocking and feeding in the fiddler crab (UCA tangeri): prey availability as risk-taking behaviour

Ens, B.J., Klaassen, M. and Zwarts, L. 1993, Flocking and feeding in the fiddler crab (UCA tangeri): prey availability as risk-taking behaviour, Netherlands journal of sea research, vol. 31, no. 4, pp. 477-494, doi: 10.1016/0077-7579(93)90060-6.

Attached Files
Name Description MIMEType Size Downloads

Title Flocking and feeding in the fiddler crab (UCA tangeri): prey availability as risk-taking behaviour
Author(s) Ens, B.J.
Klaassen, M.ORCID iD for Klaassen, M. orcid.org/0000-0003-3907-9599
Zwarts, L.
Journal name Netherlands journal of sea research
Volume number 31
Issue number 4
Start page 477
End page 494
Total pages 18
Publisher Elsevier
Place of publication Amsterdam, The Netherlands
Publication date 1993-12
ISSN 0077-7579
Keyword(s) Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Marine & Freshwater Biology
Summary For a full understanding of prey availability, it is necessary to study risk-taking behaviour of the prey. Fiddler crabs are ideally suited for such a study, as they have to leave their safe burrow to feed on the surface of the intertidal flats during low tide, thereby exposing themselves to avian predators. A study in an intertidal area along the coast of Mauritania showed that small crabs always stayed in the vicinity of their burrow, but large crabs wandered in large flocks (also referred to as droves) to feed on sea-grass beds downshore. Transplanting downshore feeding substrate to the burrowing zone of the small crabs proved that they too preferred to feed on it. Since small crabs can be preyed upon by more species of birds, this suggests that the decision not to leave the burrowing zone might be related to the risk of being fed upon by birds. We calculated predation risk from measurements on the density and feeding activity of the crabs, as well as the feeding density, the intake rate and the size selection of the avian predators. Per hour on the surface, crabs in a flock were more at risk than crabs feeding near their burrow. Thus, though flocking crabs may have benefited from ‘swamping the predator’ by emerging in maximum numbers during some tides only, this did not reduce their risk of predation below that of non-flocking crabs. Furthermore we found that irrespective of activity, large crabs suffered a higher mortality per tide from avian predators than small crabs. This suggests that large crabs could not sufficiently reduce their foraging time to compensate for the increased risk while foraging in a flock, even though they probably experienced better feeding conditions than small crabs staying near their burrow. The greater energy demands of large crabs were reflected in a greater surface area grazed. Thus, with increasing size a fiddler crab has to feed further away from its burrow and so may derive less protection from staying near to it. It seems that growing big does not reduce the risk of predation for fiddler crabs, as it does in many other species with indeterminate growth. As in such species, the most probable advantage of growing big is increased mating success. Ultimately, therefore, prey availability must be understood from the life-history decisions of the prey species.
Language eng
DOI 10.1016/0077-7579(93)90060-6
Field of Research 060801 Animal Behaviour
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©1993, Elsevier
Persistent URL http://hdl.handle.net/10536/DRO/DU:30075861

Connect to link resolver
Unless expressly stated otherwise, the copyright for items in DRO is owned by the author, with all rights reserved.

Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 58 times in TR Web of Science
Scopus Citation Count Cited 61 times in Scopus
Google Scholar Search Google Scholar
Access Statistics: 175 Abstract Views, 0 File Downloads  -  Detailed Statistics
Created: Thu, 20 Aug 2015, 14:24:21 EST

Every reasonable effort has been made to ensure that permission has been obtained for items included in DRO. If you believe that your rights have been infringed by this repository, please contact drosupport@deakin.edu.au.