Abstract
Introduced species may suppress or enhance ecological functions, or they may have neutral effects in ecosystems where they replace or complement native species. Few studies, however, have explicitly tested for these trajectories, and for the effect these might have for native species. In this study, we experimentally test the trajectory and scale of change in the function of ‘carrion removal’ at different carrion loads along ocean beaches in Eastern Australia that have different numbers of introduced red foxes (Vulpes vulpes) and several species of native raptors. We hypothesized that the ‘positive’ effect of foxes on carrion removal would be greatest at high carrion loads, because competition for resources between native and introduced species is lower. Scavenger abundance, fox occurrences, and carrion consumption by these species differed widely between locations and times. Despite distinct spatial differences in the structure of vertebrate scavenger assemblages, total carrion consumption was not significantly different between locations at any carrion load. This lack of variation in functional rates indicates potential functional plasticity in the scavenger assemblage and possible functional accommodation of red foxes. Neutral fox effects on ecological functions or the ecosystem more broadly are, however, very unlikely to extend beyond carrion consumption.
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Acknowledgements
The authors acknowledge the spending help of Andreas Fischer, Hayden Borland, Tom Brook, Makeely Blanford, Cassandra Duncan, Sarah Thackwray, and Rachel Bycroft for their commitment to the deployment of copious kilograms of pungent mullet. Financial support for this study was provided by the University of the Sunshine Coast in the form of a Vice Chancellor’s bursary to ELB, SeaWorld Research and Rescue Foundation, Sekisui House, and Water Sciences Collaborative Research Network (CRN).
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EB, TS, BG, and AO conceived the idea and designed the experiments; EB, BG, TS, AO, CH, CP, and CV conducted the experiments; EB, BG, and TS analysed the data; all authors contributed equally to the interpretation of results, and editing the manuscript.
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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All applicable institutional and/or national guidelines for the care and use of animals were followed.
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The data sets generated during and/or analysed during the current study are available in the Zenodo repository; https://zenodo.org/record/1195793#.WqXRZJNuZTY.
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Communicated by Janne Sundell.
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Bingham, E.L., Gilby, B.L., Olds, A.D. et al. Functional plasticity in vertebrate scavenger assemblages in the presence of introduced competitors. Oecologia 188, 583–593 (2018). https://doi.org/10.1007/s00442-018-4217-0
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DOI: https://doi.org/10.1007/s00442-018-4217-0