Invasive carnivores alter ecological function and enhance complementarity in scavenger assemblages on ocean beaches

Brown, Marion B., Schlacher, Thomas A., Schoeman, David S., Weston, Michael A., Huijbers, Chantal M., Olds, Andrew D. and Connolly, Rod M. 2015, Invasive carnivores alter ecological function and enhance complementarity in scavenger assemblages on ocean beaches, Ecology, vol. 96, no. 10, pp. 2715-2725, doi: 10.1890/15-0027.1.

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Title Invasive carnivores alter ecological function and enhance complementarity in scavenger assemblages on ocean beaches
Author(s) Brown, Marion B.
Schlacher, Thomas A.
Schoeman, David S.
Weston, Michael A.ORCID iD for Weston, Michael A.
Huijbers, Chantal M.
Olds, Andrew D.
Connolly, Rod M.
Journal name Ecology
Volume number 96
Issue number 10
Start page 2715
End page 2725
Total pages 11
Publisher Wiley
Place of publication London, Eng.
Publication date 2015-10
ISSN 0012-9658
Keyword(s) Science & Technology
Life Sciences & Biomedicine
Environmental Sciences & Ecology
birds of prey
food webs
functional traits
invasive species
sandy beaches
Summary Species composition is expected to alter ecological function in assemblages if species traits differ strongly. Such effects are often large and persistent for nonnative carnivores invading islands. Alternatively, high similarity in traits within assemblages creates a degree of functional redundancy in ecosystems. Here we tested whether species turnover results in functional ecological equivalence or complementarity, and whether invasive carnivores on islands significantly alter such ecological function. The model system consisted of vertebrate scavengers (dominated by raptors) foraging on animal carcasses on ocean beaches on two Australian islands, one with and one without invasive red foxes (Vulpes vulpes). Partitioning of scavenging events among species, carcass removal rates, and detection speeds were quantified using camera traps baited with fish carcasses at the dune–beach interface. Complete segregation of temporal foraging niches between mammals (nocturnal) and birds (diurnal) reflects complementarity in carrion utilization. Conversely, functional redundancy exists within the bird guild where several species of raptors dominate carrion removal in a broadly similar way. As predicted, effects of red foxes were large. They substantially changed the nature and rate of the scavenging process in the system: (1) foxes consumed over half (55%) of all carrion available at night, compared with negligible mammalian foraging at night on the fox-free island, and (2) significant shifts in the composition of the scavenger assemblages consuming beach-cast carrion are the consequence of fox invasion at one island. Arguably, in the absence of other mammalian apex predators, the addition of red foxes creates a new dimension of functional complementarity in beach food webs. However, this functional complementarity added by foxes is neither benign nor neutral, as marine carrion subsidies to coastal red fox populations are likely to facilitate their persistence as exotic carnivores.
Language eng
DOI 10.1890/15-0027.1
Field of Research 060202 Community Ecology (excl Invasive Species Ecology)
Socio Economic Objective 960802 Coastal and Estuarine Flora
HERDC Research category C1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2015, Wiley
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