Invasive carnivores in marine nature reserves: do foxes and feral pigs compete with raptors
for stranded carcasses on island beaches?
Background & Rationale
Australian ecosystems are highly vulnerable to invasive species, with numerous, widespread
- and sometimes catastrophic – environmental impacts caused by exotic carnivore species
documented across the continent1. Ecological effects of invasive species are often
manifested as species extinctions, altered or contracted trophic cascades, or fundamental
shifts in food webs2. Red foxes (Vulpes vulpes) and feral pigs (Sus scrofa) are widespread and
locally-abundant invasive mammals in Queensland. Both species can substantially alter the
diversity, species composition and ecological functions in habitats they invade. Such effects
are documented from terrestrial settings, but remain unknown for coastal ecosystems2.
In Southern Queensland, two of the large barrier islands contain distinctly different species
of large mammal scavengers consuming beach-cast carrion on the islands’ ocean beaches:
feral pigs on Moreton Island, and red foxes on North Stradbroke Island. This setting
provides for a unique ‘natural experiment’ to examine the effects of invasive mammals on
key ecological processes. Specifically, we ask the question whether invasive mammals
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compete for carrion resources with native avian scavengers . These questions have clear
conservation significance as management of invasive mammals requires an understanding
of their trophic biology and the extent to which they are likely to modify local food webs or
displace native carnivores.
Fig. 1 Native vs invasive mammal
scavenger on beaches of Southern
Queensland. Top: dingo on Fraser
Island; bottom: red fox on North
Stradbroke Island (Photos: TA
Schlacher).
Objective(s)
1.) Contrast consumption rates of beach-cast carrion between islands that differ in species presence of large mammal scavengers;
2.) Examine the extent of competition for carrion resources between invasive mammals and native bird scavengers.
Approach
Synoptic field surveys, using baited (fish) IR – and motion-triggered camera traps, will be used to measure scavenging rates and the
temporal partitioning of carcass removal from beaches between raptors and invasive mammals. Camera trapping will cover 28 sites
in total, with fourteen sites distributed at intervals of ~2 km along the exposed beaches on each island. Each site will have five
carrion deployment cycles of 24 h to quantify time trajectories of carrion removal. We have extensive experience working on the
beaches of the three islands, and have used baited camera traps to study the ecology scavengers at the beach-dune interface
(http://youtu.be/-1fea7mFpf8 )4; we are thus very confident that the proposed methods will yield high-quality data consistent with
the objectives of the proposal.
Project Team & Collaboration
This is a joint proposal by the ‘Collaborative Research Network (CRN) – Water Science’ of Griffith University (GU) and the University of the Sunshine Coast (http://youtu.be/-1fea7mFpf8 ). We have wide‐ranging and extensive experience in environmental assessments, conservation biology, and coastal ecology, with matching and complementary expertise directly relevant to this proposal. The CIs working on this project are: Supervisors: Primary: A/Prof Thomas Schlacher (USC): coastal ecology, food webs of beaches and estuaries, scavenger biology ‐ raptors; Secondary: Dr Andrew OIds (USC): marine conservation planning; reserve design, reefs and reef fishes, estuarine food webs; Collaborators: Prof Rod Connolly (GU): food‐webs, coastal carbon processing, conservation planning, mangroves; Dr Chantal Huijbers (GU): urbanisation effects; animal movement; nearshore scavengers; isotope tracing; A/Prof David Schoeman (USC): numerical analysis, beach food webs, modelling, statistics, Key Literature
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Letnic M et al. Proceedings of the Royal Society B: Biological Sciences 276, 3249-3256 (2009);
Saunders GR et al. Mammal Review 40, 181-211 (2010);
Schlacher TA et al. PLoS ONE 8, e68221 (2013);
Schlacher TA et al. Acta Oecologica 48, 7-12 (2013);