Feral violence: The Pelorus experiment

In early July 2016, two male dingoes were brought by ferry to a small island called Pelorus in the Great Barrier Reef, off the coast of north Queensland, Australia, as part of an experimental ‘feral’ goat eradication project. What was remarkable about this project was that the two dingoes released on the island had been implanted with a slow-release capsule containing sodium fluoroacetate, commonly known as ‘1080’. These so-called ‘Tik Toks’, produced by a firm called Scientec, were designed to release their poison into the bodies of the dingoes in approximately 600 days, after they had served their purpose as goat exterminators. The public and political backlash that the Pelorus experiment aroused reveals a gap between the team’s ambitions to ‘set the platform’ for the conservation of ‘pristine’ islands and community sentiment concerning animal cruelty. Just how this ‘bizarre’ experiment (as it was described in State parliament) gained ethics approval is one part of this story. Another relates to implants themselves and what this ‘innovation’ (‘the stuff of horror films’ as one petitioner described it) reveals about attitudes to ‘killing for conservation’. The Pelorus experiment also shows us what is frequently concealed by eradication programmes, which is that they rely not on a single act of eradication, but a cycle of violence that we describe here as a form of ‘feral violence’. In the case of Pelorus, the ‘implants’ tipped Conservation’s motif from the romance of ‘rescuing nature’ to that of horror, imperilling the social licence that conservation projects assume.

Elucidating dingo’s ecological roles: contributions from the Pelorus Island feral goat biocontrol project

ABSTRACT Understanding the ecological roles of apex predators remains an important field of study. The influence of apex predators on ecosystems can be either profound or negligible in different situations, and uncertainty still exists about the ecological roles of most top-predators, including Australian dingoes. This uncertainly is maintained by a dearth of experimental evidence investigating their roles. Such evidence is indispensable if dingo management is to be evidence-based. In this report, we discuss a recent experiment where dingoes were released on to an island as vertebrate biocontrol tools intended to eradicate feral goats and restore native vegetation being threatened by the goats. The experiment was successful, and the dingoes reduced the goat population to one or perhaps two male goats within ~2 years. This predator introduction experiment elucidated dingo’s effects on small livestock, their per capita predation rates, and their invasiveness or their ability to adapt and change their environment. The experiment confirmed that dingoes have the capacity to decimate populations of small livestock species and trigger a trophic cascade by reducing herbivory on vegetation. We encourage further manipulative experiments to explore the ubiquity of these results in different contexts.

Interactions between dingoes and introduced wild ungulates: concepts, evidence and knowledge gaps

The dingo (Canis dingo or C. familiaris, including hybrids with feral dogs) is the apex carnivore on mainland Australia. Fifteen non-native ungulate species have established wild populations in Australia. Dingoes are managed to reduce impacts on domestic ungulates, and introduced wild ungulates are managed to reduce impacts on natural ecosystems and to minimise competition with domestic ungulates. There is speculation about the extent to which (1) dingoes limit the abundances of introduced wild ungulates, and (2) introduced wild ungulates sustain dingo populations. We reviewed the literature to identify potential ecological interactions between dingoes and introduced wild ungulates, and to synthesise evidence for interactions between dingoes and each ungulate species (including the percentage frequency occurrence (%FO) of ungulates in dingo diets). Eleven of the 15 ungulate species were recorded in the diet of dingoes, with the highest %FO occurrences reported for feral goats (73%) and cattle (60%). Two studies concluded that dingoes reduced ungulate abundances (feral goat (Capra hircus) and feral donkey (Equus asinus)), and two studies concluded that dingoes did not regulate feral pig (Sus scrofa) abundances. A fifth study concluded that dingoes exhibited a Type III functional response to increasing sambar deer (Cervus unicolor) abundances. A sixth study concluded that dingoes made relatively little use of hunter-shot sambar deer carcasses. We propose that interactions between dingoes and introduced wild ungulates depend on the sex–age classes vulnerable to dingo predation, dingo pack sizes, the availability of escape terrain for ungulates and the availability of alternative foods for dingoes. The interplay between environmental conditions and the population growth rate of ungulates, and hence their ability to sustain losses from predation, could also be important. We predict that dingoes will have most impact on the abundance of smaller ungulate species and neonates.

Comparative dietary analysis of the black-flanked rock-wallaby (Petrogale lateralis lateralis), the euro (Macropus robustus erubescens) and the feral goat (Capra hircus) from Cape Range National Park, Western Australia

The black-flanked rock-wallaby (Petrogale lateralis lateralis) is a threatened species, once widespread throughout Western Australia but now restricted to disjunct populations including those of Cape Range National Park. It is a herbivore with a foraging range restricted to rocky outcrops and, as such, may be impacted by competition for resources from other native or introduced herbivores. This study compared the diet of the black-flanked rock-wallaby with those of co-occurring species, the euro (Macropus robustus erubescens) and the feral goat (Capra hircus), from two gorges at Cape Range National Park, to determine whether there is overlap in dietary niches. Diet composition was determined using microhistological analysis of faecal pellets in comparison with reference plant material. The black-flanked rock-wallaby diet consisted predominately of browse/forbs with some variation across seasons (63% in summer months; 74% in winter months); this overlapped significantly with the diet of goats (Schoener Index: 0.79–0.88), but not euros (SI: 0.41–0.57), whose diet consisted predominantly of grasses (72–78%). There was, however, a significant overlap in the consumption of plants with stellate hairs for all three herbivores (SI: 0.89–0.98). Dietary overlap between rock-wallabies and goats may indicate a mechanism for competition, supporting continuing measures for reduction of goat numbers in Cape Range National Park.