Effects of predation on diel activity and habitat

Authors: Nicolas C Ory David Dudgeon Nicolas Duprey Martin Thiel

Publish Date: 2014/05/17

Volume: 33, Issue: 3, Pages: 639-650

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Abstract

Nonlethal effects of predators on prey behaviour are still poorly understood although they may have cascading effects through food webs Underwater observations and experiments were conducted on a shallow fringing coral reef in Malaysia to examine whether predation risks affect diel activity habitat use and survival of the rhynchocinetid shrimp Cinetorhynchus hendersoni The study site was within a protected area where predatory fish were abundant Visual surveys and tethering experiments were conducted in April–May 2010 to compare the abundance of shrimps and predatory fishes and the relative predation intensity on shrimps during day and night Shrimps were not seen during the day but came out of refuges at night when the risk of being eaten was reduced Shrimp preferences for substrata of different complexities and types were examined at night when they could be seen on the reef complex substrata were preferred while simple substrata were avoided Shrimps were abundant on highcomplexity columnar–foliate Porites rus but tended to make little use of branching Acropora spp Subsequent tethering experiments conducted during daytime in June 2013 compared the relative mortality of shrimps on simple sand–rubble massive Porites spp and complex P rus branching Acropora spp substrata under different predation risk scenarios ie different tether lengths and exposure durations The mortality of shrimps with short tethers high risk was high on all substrata while under low and intermediate predation risks long tethers shrimp mortality was reduced on complex corals relative to that on sand–rubble or massive Porites spp Overall mortality was lowest on P rus Our study indicates that predation risks constrain shrimp activity and habitat choice forcing them to hide deep inside complex substrata during the day Such behavioural responses to predation risks and their consequences for the trophic role of invertebrate mesoconsumers warrant further investigation especially in areas where predatory fishes have been overexploitedThis study was financed by the Swire Educational Trust John Swire Sons Hong Kong Ltd and was part of a PhD project by NCO We are grateful to Clement Dumont who initiated the study of the biology of rhynchocinetid shrimps in Southeast Asia and encouraged this study We thank Kee Alfian Adzis for logistical assistance and the Malaysian Ministry of the Natural Resources and the Environment for allowing us to work in Tioman Marine Park We are also grateful to Katie Yewdall Rosie Cotton and members of Tioman Dive Centre and East Divers in Tekek for their kindness and professionalism Solomon Chak for his assistance during 2010 Daniel Pedraza for his help during field experiments and Raymond Bauer for the identification of C hendersoni We acknowledge the constant support of Evelyn Lostarnau and her design and construction of tools for the 2013 fieldwork

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