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Habitat-former effects on prey behaviour increase predation and non-predation mortality


Gribben, PE and Wright, JT, Habitat-former effects on prey behaviour increase predation and non-predation mortality, Journal of Animal Ecology, 83, (2) pp. 388-396. ISSN 0021-8790 (2014) [Refereed Article]

Copyright Statement

Copyright 2013 The Authors

DOI: doi:10.1111/1365-2656.12139


  • Habitat-forming species can influence mortality on associated species via altering structural and non-structural abiotic conditions. Importantly, these effects can occur simultaneously and in opposite directions, although how they contribute to the net outcomes for predator–prey interactions remain unexplored.

  • Seagrasses often have positive effects on associated fauna because their structure directly reduces predator encounter rates. However, we identified a ‘risky’ behaviour (shallower burial) in an infaunal bivalve at a high seagrass cover – likely induced by non-structural abiotic change – suggesting positive effects may be outweighed by risky behaviours. We determined whether the physical structure of the seagrass interacted with burial behaviour of clams to determine the predation and non-predation mortality and whether these interactions were mediated by the cover of the seagrass.

  • Surveys on an intertidal sand flat in Tasmania, Australia showed that the highest densities of a dominant bivalve, Katelysia scalarina, occurred at low (33%) seagrass cover, but the lowest densities and the highest proportion of unburied clams occurred at high (100%) cover. A field experiment manipulating burial depth, seagrass cover and predator access demonstrated that unburied clams suffered very high predation and non-predation mortality compared to buried clams (~4x higher), which outweighed any positive effects of the seagrass structure in reducing predator access. Being unburied also had non-lethal consequences with surviving unburied clams having a reduced tissue biomass compared to buried clams.

  • In this system, predation was driven by the availability of prey when they undertake a risky behaviour (shallow burial). However, significant changes in behaviour may only occur once a threshold of habitat-former density is reached. In this instance, changes in behaviour were likely due to seagrass effects on sediment redox potential, which decreased significantly above 33% seagrass cover.

  • Our findings demonstrate that the negative effects of a habitat-former on the behaviour of associated species, via alteration of non-structural abiotic conditions, can outweigh any positive effects provided by increasing habitat structure as is commonly reported for habitat-formers.

  • Item Details

    Item Type:Refereed Article
    Keywords:behaviourally meditated indirect effects, clams, density dependence, ecosystem engineers, foundation species, seagrass, trophic interactions
    Research Division:Biological Sciences
    Research Group:Ecology
    Research Field:Marine and estuarine ecology (incl. marine ichthyology)
    Objective Division:Environmental Management
    Objective Group:Marine systems and management
    Objective Field:Marine biodiversity
    UTAS Author:Wright, JT (Associate Professor Jeffrey Wright)
    ID Code:96873
    Year Published:2014
    Web of Science® Times Cited:13
    Deposited By:NC Marine Conservation and Resource Sustainability
    Deposited On:2014-11-25
    Last Modified:2017-10-31

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