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

journal contribution
posted on 2023-05-18, 05:24 authored by Gribben, PE, Jeffrey WrightJeffrey Wright
  • 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.

  • History

    Publication title

    Journal of Animal Ecology








    Institute for Marine and Antarctic Studies


    Blackwell Publishing Ltd

    Place of publication

    9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

    Rights statement

    Copyright 2013 The Authors

    Repository Status

    • Restricted

    Socio-economic Objectives

    Marine biodiversity

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