John L. Read

Interactions between a top order predator and exotic mesopredators in the Australian rangelands.

An increase in mesopredators caused by the removal of top-order predators can have significant implications for threatened wildlife. Recent evidence suggests that Australia’s top-order predator, the dingo, may suppress the introduced cat and red fox. We tested this relationship by reintroducing 7 foxes and 6 feral cats into a 37 km2 fenced paddock in arid South Australia inhabited by a male and female dingo. GPS datalogger collars recorded locations of all experimental animals every 2 hours. Interactions between species, mortality rates, and postmortems were used to determine the mechanisms of any suppression. Dingoes killed all 7 foxes within 17 days of their introduction and no pre-death interactions were recorded. All 6 feral cats died between 20 and 103 days after release and dingoes were implicated in the deaths of at least 3 cats. Dingoes typically stayed with fox and cat carcasses for several hours after death and/or returned several times in ensuing days. There was no evidence of intraguild predation, interference competition was the dominant mechanism of suppression. Our results support anecdotal evidence that dingoes may suppress exotic mesopredators, particularly foxes. We outline further research required to determine if this suppression translates into a net benefit for threatened prey species.

More than Mere Numbers: The Impact of Lethal Control on the Social Stability of a Top-Order Predator

Population control of socially complex species may have profound ecological implications that remain largely invisible if only their abundance is considered. Here we discuss the effects of control on a socially complex top-order predator, the dingo (Canis lupus dingo). Since European occupation of Australia, dingoes have been controlled over much of the continent. Our aim was to investigate the effects of control on their abundance and social stability. We hypothesized that dingo abundance and social stability are not linearly related, and proposed a theoretical model in which dingo populations may fluctuate between three main states: (A) below carrying capacity and socially fractured, (B) above carrying capacity and socially fractured, or (C) at carrying capacity and socially stable. We predicted that lethal control would drive dingoes into the unstable states A or B, and that relaxation of control would allow recovery towards C. We tested our predictions by surveying relative abundance (track density) and indicators of social stability (scent-marking and howling) at seven sites in the arid zone subject to differing degrees of control. We also monitored changes in dingo abundance and social stability following relaxation and intensification of control. Sites where dingoes had been controlled within the previous two years were characterized by low scent-marking activity, but abundance was similar at sites with and without control. Signs of social stability steadily increased the longer an area was allowed to recover from control, but change in abundance did not follow a consistent path. Comparison of abundance and stability among all sites and years demonstrated that control severely fractures social groups, but that the effect of control on abundance was neither consistent nor predictable. Management decisions involving large social predators must therefore consider social stability to ensure their conservation and ecological functioning.

Rabbit biocontrol and landscape‐scale recovery of threatened desert mammals

Funding for species conservation is insufficient to meet the current challenges facing global biodiversity, yet many programs use expensive single-species recovery actions and neglect broader management that addresses threatening processes. Arid Australia has the worlds worst modern mammalian extinction record, largely attributable to competition from introduced herbivores, particularly European rabbits (Oryctolagus cuniculus) and predation by feral cats (Felis catus) and foxes (Vulpes vulpes). The biological control agent rabbit hemorrhagic disease virus (RHDV) was introduced to Australia in 1995 and resulted in dramatic, widespread rabbit suppression. We compared the area of occupancy and extent of occurrence of 4 extant species of small mammals before and after RHDV outbreak, relative to rainfall, sampling effort, and rabbit and predator populations. Despite low rainfall during the first 14 years after RHDV, 2 native rodents listed by the International Union for Conservation of Nature (IUCN), the dusky hopping-mouse (Notomys fuscus) and plains mouse (Pseudomys australis), increased their extent of occurrence by 241-365%. A threatened marsupial micropredator, the crest-tailed mulgara (Dasycercus cristicauda), underwent a 70-fold increase in extent of occurrence and a 20-fold increase in area of occupancy. Both bottom-up and top-down trophic effects were attributed to RHDV, namely decreased competition for food resources and declines in rabbit-dependent predators. Based on these sustained increases, these 3 previously threatened species now qualify for threat-category downgrading on the IUCN Red List. These recoveries are on a scale rarely documented in mammals and give impetus to programs aimed at targeted use of RHDV in Australia, rather than simply employing top-down threat-based management of arid ecosystems. Conservation programs that take big-picture approaches to addressing threatening processes over large spatial scales should be prioritized to maximize return from scarce conservation funding. Further, these should be coupled with long-term ecological monitoring, a critical tool in detecting and understanding complex ecosystem change.

An optimised rapid detection technique for simultaneously monitoring activity of rabbits, cats, foxes and dingoes in the rangelands

A single procedure that land managers can readily use to simultaneously monitor populations of multiple pest animal species would enhance capacity to effectively manage environmental impacts in the Australian rangelands. Such a procedure should be efficient and provide a standard for data collection, enabling meaningful evaluation of changes through time. This study compared the efficiency of two indices, namely spotlight counts and a variety of passive activity indices, for detecting rabbit, cat, fox and dingo activity. Spotlight counts were more practical for estimating rabbit activity but were poor indicators of cat, fox or dingo activity. Records of animal tracks on discrete 200 m dirt road segments with favourable substrate and separated by at least 2 km are considered optimal for collectively monitoring relative changes through time in rabbit, cat, fox and dingo activity.

The use of poison baits to control feral cats and red foxes in arid South Australia: II. Bait type, placement, lures and non-target uptake.

Context Poison baits are often used to control both foxes and feral cats but success varies considerably. Aims This study investigated the influence of bait type, placement and lures on bait uptake by the feral cat, red fox and non-target species to improve baiting success and reduce non-target uptake. Methods Six short field trials were implemented during autumn and winter over a five-year period in northern South Australia. Key results Results suggest that poison baiting with Eradicat or dried kangaroo meat baits was inefficient for feral cats due to both low rates of bait detection and poor ingestion rates for baits that were encountered. Cats consumed more baits on dunes than swales and uptake was higher under bushes than in open areas. The use of auditory or olfactory lures adjacent to baits did not increase ingestion rates. Foxes consumed more baits encountered than cats and exhibited no preference between Eradicat and kangaroo meat baits. Bait uptake by native non-target species averaged between 14 and 57% of baits during the six trials, accounting for up to 90% of total bait uptake. Corvid species were primarily responsible for non-target uptake. Threatened mammal species investigated and nibbled baits but rarely consumed them; however, corvids and some common rodent species ingested enough poison to potentially receive a lethal dose. Conclusions It is likely that several factors contributed to poor bait uptake by cats including the presence of alternative prey, a preference for live prey, an aversion to scavenging or eating unfamiliar foods and a stronger reliance on visual rather than olfactory cues for locating food. Implications Further trials for control of feral cats should concentrate on increasing ingestion rates without the requirement for hunger through either involuntary ingestion via grooming or development of a highly palatable bait.

Status of warru (Petrogale lateralis MacDonnell Ranges race) in the Anangu Pitjantjatjara Yankunytjatjara Lands of South Australia. 1. Distribution and decline

Surveys for warru (Petrogale lateralis MacDonnell Ranges race) were conducted in targeted areas of the Anangu Pitjantjatjara Yankunytjatjara (APY) Lands in order to clarify the distribution and status of the taxon in South Australia. Presence was determined by animal sightings or fresh scats. The study identified extant warru sites adjacent to known colonies in the Musgrave and Tomkinson Ranges, indicating that, in both locations, warru probably occur as larger metapopulations. The study highlighted that warru has disappeared from 93% of its former range across South Australia, and from 88% of its stronghold in the APY Lands. Accounting for recent information on population dynamics, this study has confirmed that warru are ‘Endangered’ in South Australia, and a more thorough assessment of the race’s current national distribution and status is required.

Bringing back warru: initiation and implementation of the South Australian Warru Recovery Plan

The warru, or black-footed rock-wallaby (Petrogale lateralis MacDonnell Ranges race), has continued to declined dramatically in range and abundance in South Australia over the last 80 years, and is now considered to be one of the state’s most endangered species. This paper documents key indicators of this decline and provides context for both the formation of the Warru Recovery Team, and the development of the objectives and actions of the Warru Recovery Plan. Warru decline is considered to be a symptom of ecosystem dysfunction in the central Australian ranges, yet warru recovery provides an opportunity for broadscale ecosystem recovery in this remote region. Full engagement of Anangu, research-based adaptive ecosystem management, and inclusive, strategic and sustainable management of the recovery process, are considered integral to meeting the objectives of the Warru Recovery Plan.

The effects of browsing by feral and re-introduced native herbivores on seedling survivorship in the Australian rangelands

Browsing by introduced cattle (Bos taurus) and rabbits (Oryctolagus cuniculus) can limit the recruitment of some arid zone tree and shrub species. In a study conducted at the Arid Recovery Reserve, Roxby Downs, SA, we aimed to quantify initial recruitment changes in shrubs after the removal of cattle and rabbits and the re-introduction of locally extinct fauna. The presence and abundance of seedlings was measured at groves of seven native perennial shrubs over 6 years under four browsing treatments: (1) ‘reserve-reintroductions’ [re-introduced greater stick-nest rats (Leporillus conditor), burrowing bettongs (Bettongia lesueur) and greater bilbies (Macrotis lagotis)], (2) ‘reserve-no browsers’, (3) ‘pastoral-stocked’ (rabbits and cattle), and (4) ‘pastoral-destocked’ (rabbits). Recruitment of mulga (Acacia aneura F.Muell. ex Benth.), silver cassia (Senna artemisioides subsp. petiolaris Randell) and sandhill wattle (Acacia ligulata A.Cunn. ex Benth.) was significantly greater in the two browsing regimes inside the Reserve than in the two pastoral regimes. The number of recruits of these three species declined at ‘pastoral-destocked’ and ‘pastoral-stocked’ sites but increased at ‘reserve-reintroductions’ and ‘reserve-no browsers’ sites from 2001 to 2006. Narrow-leaf hopbush (Dodonaea viscose (L.) Jacq.) showed a trend towards increased recruitment at sites in both browsing regimes inside the Reserve, but decreased recruitment at sites in both pastoral regimes. Native plum (Santalum lanceolatum R.Br.), native apricot (Pittosporum phylliraeoides orth. var. DC.) and bullock bush (Alectryon oleifolius (Desf.) S.T.Reynolds) exhibited no significant difference in recruitment between the four browsing regimes within the study timeframe. These results suggest that excluding rabbits and stock may benefit the germination and survival of mulga, silver cassia and sandhill wattle. To date, re-introduced native herbivores at low numbers have not been found to negatively affect the recruitment or growth rate of the seven perennial plant species studied.

Additional records of small mammals in northern South Australia

Analysis of prey remains found in predator scats is a valuable tool for assessing the distribution and status of small mammal populations. As part of a large-scale dingo research project in northern South Australia, the prey remains found in 1845 dingo scats were analysed. A range of species were identified as expected, though, of particular interest, additional records of Rattus villosissimus, Notomys fuscus and Pseudomys australis were obtained. Our R. villosissimus records confirm the contemporary range of this species in the north-eastern pastoral zone, while our N. fuscus records support other recent records of this species in the same area. Our P. australis record indicates that an isolated population of this species exists in the Strzelecki Desert, ∼400km east of the nearest known population. The status of these populations remains unknown, including the risk of dingo predation to them.

A framework for assessing regional biodiversity condition under changing environments of the arid Australian rangelands

Rangelands support many ecosystem services important to humans, including climate regulation. They also have a significant role to play in the mitigation of greenhouse gases. However, the capacity of any rangeland to do this depends foremost upon the condition of biodiversity, and the functioning of its ecosystems. Considerable research has been undertaken on rangeland condition but it has not yet included the assessment of biodiversity (plants, animals and microbes) as a primary focus. Rangeland managers have struggled to assess biodiversity condition because it is rarely defined, is everywhere (so what do you assess?), is always changing in response to natural and human disturbances (so how do you know when it has changed?) and what amount signals management action. Here we present a framework that addresses these issues, and apply it to select surrogates and indicators that are scientifically defensible in biological and planning terms for assessing biodiversity. An arid Australian rangeland region is used as a case study to develop and apply our approach. We were not able to illustrate interpretation of condition because of the absence of long-term monitoring data in Australian rangelands, but we do provide guiding principles about sampling design and analytical methods for interpretation that use raw data rather than multimetrics. We discovered that different management outcomes expected to be informed from assessing biodiversity condition affected surrogate and indicator choice, and that a number indicators were not robust when assessed on conceptual relevance, measurement qualities, feasibility of implementation and policy and management relevance for four different management outcomes. Our work highlights the importance of stating the expected outcomes of biodiversity condition assessments up front, so that indicators relevant to future management are chosen. It also shows that critical thought on the robustness of indicators is warranted, especially as condition assessments under climate change will require information on the functional traits of species. We conclude by assessing the strengths and weaknesses of our framework in relation to environmental planning.