Sniffing out danger: rapid antipredator training of an endangered marsupial

Globally, predator aversion training has assisted naive prey species to learn to evade introduced predators, improving translocation success. Eastern barred bandicoots (Perameles gunnii; hereafter ‘bandicoot’) are extinct on mainland Australia due to habitat loss and introduced predators, and are the focus of a long-term captive breeding and reintroduction program. Our trials showed that captive bandicoots failed to recognise cat (Felis catus) scents as belonging to a predator, suggesting prey naivety towards cats. We trialled five stimuli to elicit short-term fear behaviour in bandicoots. An automatic compressed air spray and automatic bin lid were most effective. We coupled these stimuli with cat urine during predator aversion training and presented them to bandicoots on three occasions. Bandicoots learnt to avoid the area containing cat urine, suggesting bandicoots are capable of learning new behaviours rapidly. Six trained and five untrained captive bandicoots where released onto Summerland Peninsular, Phillip Island (with cat densities at 1.1 cats/km2). Both had high survival and recapture rates 7 months after release. Training endangered species to avoid introduced predators could assist with long-term species recovery.

The canid pest ejector challenge: controlling urban foxes while keeping domestic dogs safe

Abstract ContextIt is widely recognised that red foxes (Vulpes vulpes) are abundant within urban areas; however, it is difficult to apply lethal control measures using poison baits in cities because of concerns about the safety of domestic pets, particularly dogs (Canis familiaris). AimsWe tested canid pest ejectors (CPEs) as a potential method of fox control by measuring visitation and activation behaviour of foxes and other wildlife while assessing non-target risk to domestic dogs. MethodsWe compared eight urban and eight peri-urban sites in Sydney, with half of the sites having restricted access for domestic dogs. We allocated five camera traps and ejectors per site. Through generalised linear mixed models, we compared the probability of ejector activation between foxes and dogs. We also assessed the relationship between dog visitation and distance to habitation and dog restrictions as measures of dog safety. Key resultsBoth species of canids were equally likely to pull the ejector (P=0.26). As expected, dog visitation was significantly lower in sites with dog restrictions (P<0.001). However, it was not related to distance from habitation. Only two non-canid species were recorded pulling the ejector, suggesting high target-specificity for canids. ConclusionsIn sites with dog restrictions, the risk of dog casualties from CPEs is minimal. However, distance from habitation does not increase dog safety, at least within 250m. The ejector is highly specific for canids. ImplicationsWe provide specific recommendations for the design of a potential fox control program using CPEs in urban and peri-urban areas. The ejector may be a safe method for fox control in cities when deployed at places without domestic dogs.

Circadian rhythms enable efficient resource selection in a human-modified landscape

Animals access resources such as food and shelter, and acquiring these resources has varying risks and benefits, depending on the suitability of the landscape. Some animals change their patterns of resource selection in space and time to optimize the trade-off between risks and benefits. We examine the circadian variation in resource selection of swamp wallabies (Wallabia bicolor) within a human-modified landscape, an environment of varying suitability. We used GPS data from 48 swamp wallabies to compare the use of landscape features such as woodland and scrub, housing estates, farmland, coastal areas, wetlands, waterbodies, and roads to their availability using generalized linear mixed models. We investigated which features were selected by wallabies and determined whether the distance to different landscape features changed, depending on the time of the day. During the day, wallabies were more likely to be found within or near natural landscape features such as woodlands and scrub, wetlands, and coastal vegetation, while avoiding landscape features that may be perceived as more risky (roads, housing, waterbodies, and farmland), but those features were selected more at night. Finally, we mapped our results to predict habitat suitability for swamp wallabies in human-modified landscapes. We showed that wallabies living in a human-modified landscape selected different landscape features during day or night. Changing circadian patterns of resource selection might enhance the persistence of species in landscapes where resources are fragmented and disturbed.

Drought increases the impact of introduced European foxes on breeding Australian pelicans

Context Introduced mammalian predators have been responsible for population declines in native prey species around the world. Many conservation programs rely on control or eradication of introduced mammalian predators, but the impact of environmental variation on the efficacy of this approach is rarely documented. Aims The present paper describes (1) the impact of introduced European foxes (Vulpes vulpes) on breeding Australian pelicans (Pelecanus conspicillatus) in South Australia and (2) the responses of both species to a fox-eradication program using a before-after-impact framework. Methods The impact of foxes on breeding Australian pelicans was studied on a near-shore island. An index of fox abundance and direct measurements of breeding pelicans and mortality of pelican eggs and young were compared before foxes were established on the island, while foxes were resident and during a fox-eradication program. A path analysis was used to explore the causal relationships between fox abundance and other potential covariates (e.g. rainfall) on breeding pelicans. Key results Before foxes were established on the island, the number of breeding pelicans grew and egg mortality was low. While foxes were resident, the number of breeding pelicans fell and egg mortality rose. This was followed by an increase in the number of breeding pelicans and a decrease in egg mortality during a fox-eradication program. While foxes had a clear impact on egg mortality, a period of low rainfall also occurred while foxes were resident. The path analysis showed an interaction among rainfall, size of the pelican breeding population and the impact of foxes. In drought years, fewer pelicans bred and foxes were a major cause of nest abandonment when they entered pelican breeding colonies to prey on eggs. Conclusions These results confirmed that foxes can be an important predator of ground-nesting, colonial waterbirds, and showed that the impact of foxes may be higher in drought years when prey populations are low. Implications The present study suggests that an increase in the incidence of droughts as a result of climate change may increase the impact of introduced predators on drought-sensitive waterbirds and raises the possibility of focussing predator-control efforts during droughts, as periods of particular risk to colony-breeding waterbirds.

Impacts of Mesopredator Control on Conservation of Mesopredators and Their Prey

Declining large carnivore populations, increased habitat fragmentation, declining interests in fur trapping, and other anthropogenic factors can all lead to increased mesopredator populations and these may negatively impact biodiversity. Lethal mesopredator control potentially mitigates some of these effects but can be controversial, largely because impacts on mesopredator populations have not been evaluated. Estimating these impacts may reduce controversies while increasing our understanding of when lethal control may be beneficial. Therefore, we analyzed published mesopredator removal data to determine if mesopredator removal rates changed over time. Removals of medium,(e.g., raccoons (Procyon lotor) or red foxes (Vulpes vulpes), and large, i.e., bobcats (Lynx rufus) or coyotes (Canis latrans), mesopredators were consistent from year to year and over the duration of study (i.e., number removed during the first and last years of studies were similar). In contrast, removals of small mesopredators, e.g., weasels (Mustela spp.) or spotted skunks (Spilogale putorius), declined over the duration of study. Study area size, number of species targeted for removal, and duration of removal effort were poor predictors of removal rates. Our analyses suggest that: (1) control, as typically implemented, is unlikely to cause negative long-term impacts on populations of medium and large mesopredators but may negatively impact small mesopredators, (2) if mesopredator control benefits prey, recurring removals will generally be needed to maintain benefits, and (3) timing of removals will be important to achieve management goals. We suggest that mesopredator control efforts are frequently spatially structured harvests from continuously distributed populations. This may explain (1) why removal of small mesopredators declined over time; whereas, medium and large mesopredator removals remained consistent, and (2) why some prey failed to respond to mesopredator control efforts.

Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins

Context Egg depredation is a major cause of reproductive failure among birds and can drive population declines. In this study we investigate predatory behaviour of a corvid (little raven; Corvus mellori) that has only recently emerged, leading to widespread and intense depredation of eggs of a burrow-nesting seabird (little penguin; Eudyptula minor). Aims The main objective of this study was to measure the rate of penguin egg depredation by ravens to determine potential threat severity. We also examined whether penguin burrow characteristics were associated with the risk of egg depredation. Ravens generally employ two modes of predatory behaviour when attacking penguin nests; thus we examined whether burrow characteristics were associated with these modes of attack. Methods Remote-sensing cameras were deployed on penguin burrows to determine egg predation rates. Burrow measurements, including burrow entrance and tunnel characteristics, were measured at the time of camera deployment. Key results Overall, clutches in 61% of monitored burrows (n = 203) were depredated by ravens, the only predator detected by camera traps. Analysis of burrow characteristics revealed two distinct types of burrows, only one of which was associated with egg depredation by ravens. Clutches depredated by ravens had burrows with wider and higher entrances, thinner soil or vegetation layer above the egg chamber, shorter and curved tunnels and greater areas of bare ground and whitewash near entrances. In addition, 86% were covered by bower spinach (Tetragonia implexicoma), through which ravens could excavate. Ravens used two modes to access the eggs: they attacked through the entrance (25% of burrow attacks, n = 124); or dug a hole through the burrow roof (75% of attacks, n = 124). Burrows that were subject to attack through the entrance had significantly shorter tunnels than burrows accessed through the roof. Conclusions The high rates of clutch loss recorded here highlight the need for population viability analysis of penguins to assess the effect of egg predation on population growth rates. Implications The subterranean foraging niche of a corvid described here may have implications for burrow-nesting species worldwide because many corvid populations are increasing, and they exhibit great capacity to adopt new foraging strategies to exploit novel prey.