Habitat selection by feral cats and dingoes in a semi‐arid woodland environment in central Australia

Habitat use by feral cats and dingoes was examined within a heterogeneous semi‐arid woodland site in central Australia over 2 years. Density estimates of feral cats based on tracks were higher in mulga habitat than in open habitat. Isodar analysis implied that this pattern of habitat use by feral cats was consistent with the consumer‐resource model of density‐dependent habitat selection, which is an ideal free solution. The reason why mulga supported higher densities of feral cats was unclear. Foraging success of feral cats may be higher in the mulga because the stalk and ambush hunting tactics typically employed by felids are well suited to dense cover. Mulga may also have offered feral cats more protection from dingo predation. Dingo activity was distributed uniformly across habitats. The dingo isodar was statistically non‐significant, suggesting that habitat selection by dingoes was independent of density.     

The development of target‐specific vertebrate pest management tools for complex faunal communities

Summary The efficacy of vertebrate pest control in complex faunal communities can be compromised by adverse impacts on non‐target species. We present a five‐step framework to guide the design of pest control programmes to overcome this constraint. The model consists of: (i) selection of the most appropriate basis for control; (ii) identification of opportunities to prevent non‐target species from interacting with control activities; (iii) classification of non‐target species by dissimilarity to the target pest; (iv) use of a recognition systems approach to identify further differences between pests and non‐target species; and (v) experimental evaluation of prototype control methodologies. Application of the framework to the problem of feral Pig (Sus scrofa) control in the tropical forests of the Daintree region in north Queensland identified six design features which, if successfully evaluated and implemented, could allow the implementation of strategic, sustained Pig control using poison baits where it has previously been unacceptable.     

Present Government policy on pest control

Abstract

The staff of Environment Waikato are to be congratulated for their initiative in setting up this important meeting. More public discussion on the pest problem in New Zealand is needed, although my mailbag suggests that there is already a keen awareness of the daunting problem that we face.

The possum is most often cast in the villain's role, but we should not ignore the rats, rabbits, deer, feral sheep, pigs, cats, mustelids, wasps, and feral cattle that are also pests in some ecosystems.     

Modern approaches for the biological control of vertebrate pests: An Australian perspective

Vertebrate pests cost Australia at least $1 billion annually in lost agricultural production and environmental damage. The spectacular success of myxomatosis in the 1950s and more recently, rabbit hemorrhagic disease, in the biological control of European rabbits has led to ongoing research into similar solutions for other vertebrate pests. There are significant barriers to the successful employment of biological control options including the obvious technological ones, such as host-specificity, as well as the investment required, public concerns and regulatory requirements. The role of biological control in vertebrate pest management and the attempts to develop such strategies in Australia is reviewed with emphasis on species specific case studies for rabbits, cane toads and carp, and the generic approaches of immunocontraception and daughterless genes.     

Linking pasture, livestock productivity and vertebrate pest management

The study of pastures, pests (rabbits and caterpillars) and sheep productivity by Barlow (1987; New Zeal J Ecol 10: 43–55) is reviewed, updated and extended. Pasture growth was modelled as a dynamic process, though sheep and rabbit abundance were not dynamic. The model predicted that there was a parabolic relationship between sheep productivity and sheep stocking rate with the effects of rabbits being to shift the relationship lower and to the left. The relationship is analogous to a model of sustained harvest of a wild population, and the shape parameter of each has similar numerical values (2 to 3). The Barlow model also predicted a negative relationship between sheep productivity and rabbit abundance, with the relationship being curved with fixed stocking rates. Analysis of data from an independent experimental study shows more support for a negative quadratic (concave down, R2 = 0.509) than a negative linear (R2 = 0.416, ΔAICc = 2.770) relationship. The Barlow (1987) study assumed a positive linear relationship between the area of denuded pasture and pest abundance. A model selection analysis of a priori models of disturbance by feral pigs provides support for a positive curved relationship (R2 = 0.854) and a positive linear relationship (R2 = 0.357; ΔAICc = 0.03) between the area of denuded pasture (as disturbed ground) and pig abundance. The general results and their implications are discussed.     

Testing target‐specific bait delivery for controlling feral pigs in a tropical rainforest

Mitigation of feral pig (Sus scrofa) impacts in Australia’s Wet Tropics World Heritage Area has been impeded by the lack of a target‐specific method for delivering toxic baits in the region. This study evaluated methods to reduce bait‐take by susceptible nontarget species without inhibiting bait‐take by pigs, to enable more effective pig management. We predicted that dingoes would not select an unprocessed corn bait and that other potential nontarget bait consumers would be unable to access the same bait presented under a lightweight cover. Neither of these methods was expected to reduce bait selection or access by pigs. We tested these predictions by monitoring animal interactions with covered and uncovered corn baits, and covered corn and manufactured baits. Use of corn as a bait substrate effectively prevented bait‐take by dingoes. Covering baits substantially reduced bait‐take by other nontarget species and completely prevented nontarget bait‐take when uncovered feed was provided simultaneously. The corn bait preparation was highly acceptable and accessible to feral pigs. We conclude that the methods evaluated here could enable the consideration of poison baiting as a viable method for controlling feral pigs in the World Heritage Area, where it has previously been unavailable.     

Do dingoes suppress the activity of feral cats in northern Australia?

Large predators can have profound impacts on community composition. Not only do they directly affect prey abundance, they also indirectly affect prey abundance through their direct effects on smaller predators. In Australia, dingoes fill the role of a large predator and, in southern Australia, have clear impacts on introduced foxes. Their effect on introduced cats, however, is less clear. Here we present data from multiple sites across northern Australia (where foxes are absent), which reveal a negative correlation between cat and dingo activity. This relationship could arise because cats avoid areas where dingoes are active, or because cats are less abundant in areas with high dingo densities, or a combination of both. At a subset of our study sites, we experimentally reduced dingo (but not cat) abundance by poison baiting. This resulted in a 55% drop in dingo activity within 4 weeks of baiting, but without a compensatory increase in cat activity. This suggests the negative correlation between cat and dingo activity is not a simple consequence of cats reactively avoiding areas with higher dingo traffic, but rather, that there are fewer cats in areas where dingoes are more active. This study is a rare demonstration of the potential for dingoes to affect the behaviour and potentially the population size of feral cats, and therefore reduce the impact of feral cats on vulnerable native prey species.     

Estimating abundances,densities, and interspecific associations in a carnivore community

Estimating population abundances, densities, and interspecific interactions are common goals in wildlife management. Camera traps have been used to estimate the abundance and density of a single species, and are useful for carnivores that occur at low densities. Spatial capture–recapture (SCR) models can be used to estimate abundance and density from a camera trap array when all, some, or no individuals in the population can be uniquely identified. These SCR models also estimate locations of individual activity centers, the spatial patterning of which could provide important information about interspecific interactions. We used SCR models to estimate abundances, densities, and activity centers of each of 3 carnivore species (i.e., dingo [Canis familiaris], red fox [Vulpes vulpes], and feral cat) using photographs from 1 camera trap array in southeastern Australia during September to November 2015. Some dingoes and feral cats were uniquely identifiable and therefore, we used a spatial mark–resight model for these species. We could not uniquely identify fox individuals, however, so we used a spatial unmarked (SUN) model for this species. Our estimated dingo density was 0.06/km². The fox (0.25/km²) and feral cat (0.16/km²) densities are within the ranges previously reported for these species in Australia. We obtained a relatively imprecise fox density estimate because we did not have detections of uniquely identifiable individuals; hence, the SUN model should be used as a last resort. We next modeled spatial dependence among the estimated activity centers for the 3 species using a spatial pair correlation function for a marked point process. Consistent with our expectations, the activity centers of dingoes and foxes were strongly negatively associated at distances of <1,000 m. Foxes and feral cats were also negatively associated at distances of <1,500 m. Surprisingly, dingoes and feral cats were positively associated at distances of >500 m, with no association evident at distances of <500 m. Our study extends the inferences that can be made from using a camera trap array and SCR methods to include spatial patterning and interspecific interactions, and provides new insights into the carnivore community of dingoes, foxes, and feral cats in southeastern Australia. © 2019 The Authors. The Journal of Wildlife Management Published by Wiley Periodicals, Inc.     

Resolving the value of the dingo in ecological restoration

There is global interest in restoring populations of apex predators, both to conserve them and to harness their ecological services. In Australia, reintroduction of dingoes (Canis dingo) has been proposed to help restore degraded rangelands. This proposal is based on theories and the results of studies suggesting that dingoes can suppress populations of prey (especially medium‐ and large‐sized herbivores) and invasive predators such as red foxes (Vulpes vulpes) and feral cats (Felis catus) that prey on threatened native species. However, the idea of dingo reintroduction has met opposition, especially from scientists who query the dingo's positive effects for some species or in some environments. Here, we ask ‘what is a feasible experimental design for assessing the role of dingoes in ecological restoration?’ We outline and propose a dingo reintroduction experiment—one that draws upon the existing dingo‐proof fence—and identify an area suitable for this (Sturt National Park, western New South Wales). Although challenging, this initiative would test whether dingoes can help restore Australia's rangeland biodiversity, and potentially provide proof‐of‐concept for apex predator reintroductions globally.     

Are dingoes a trophic regulator in arid Australia? A comparison of mammal communities on either side of the dingo fence

The direct and indirect interactions that large mammalian carnivores have with other species can have far‐reaching effects on ecosystems. In recent years there has been growing interest in the role that Australia's largest terrestrial predator, the dingo, may have in structuring ecosystems. In this study we investigate the effect of dingo exclusion on mammal communities, by comparing mammal assemblages where dingoes were present and absent. The study was replicated at three locations spanning 300 km in the Strzelecki Desert. We hypothesized that larger species of mammal subject to direct interactions with dingoes should increase in abundance in the absence of dingoes while smaller species subject to predation by mesopredators should decrease in abundance because of increased mesopredator impact. There were stark differences in mammal assemblages on either side of the dingo fence and the effect of dingoes appeared to scale with body size. Kangaroos and red foxes were more abundant in the absence of dingoes while Rabbits and the Dusky Hopping‐mouse Notomys fuscus were less abundant where dingoes were absent, suggesting that they may benefit from lower red fox numbers in the presence of dingoes. Feral cats and dunnarts (Sminthopsis spp.) did not respond to dingo exclusion. Our study provides evidence that dingoes do structure mammal communities in arid Australia; however, dingo exclusion is also associated with a suite of land use factors, including sheep grazing and kangaroo harvesting that may also be expected to influence kangaroo and red fox populations. Maintaining or restoring populations of dingoes may be useful strategies to mitigate the impacts of mesopredators and overgrazing by herbivores.     

Prey use by dingoes in a contested landscape: Ecosystem service provider or biodiversity threat?

In Australia, dingoes (Canis lupus dingo) have been implicated in the decline and extinction of a number of vertebrate species. The lowland Wet Tropics of Queensland, Australia is a biologically rich area with many species of rainforest‐restricted vertebrates that could be threatened by dingoes; however, the ecological impacts of dingoes in this region are poorly understood. We determined the potential threat posed by dingoes to native vertebrates in the lowland Wet Tropics using dingo scat/stomach content and stable isotope analyses of hair from dingoes and potential prey species. Common mammals dominated dingo diets. We found no evidence of predation on threatened taxa or rainforest specialists within our study areas. The most significant prey species were northern brown bandicoots (Isoodon macrourus), canefield rats (Rattus sordidus), and agile wallabies (Macropus agilis). All are common species associated with relatively open grass/woodland habitats. Stable isotope analysis suggested that prey species sourced their nutrients primarily from open habitats and that prey choice, as identified by scat/stomach analysis alone, was a poor indicator of primary foraging habitats. In general, we find that prey use by dingoes in the lowland Wet Tropics does not pose a major threat to native and/or threatened fauna, including rainforest specialists. In fact, our results suggest that dingo predation on “pest” species may represent an important ecological service that outweighs potential biodiversity threats. A more targeted approach to managing wild canids is needed if the ecosystem services they provide in these contested landscapes are to be maintained, while simultaneously avoiding negative conservation or economic impacts.     

Cranial Shape and the Modularity of Hybridization in Dingoes and Dogs; Hybridization Does Not Spell the End for Native Morphology

Australia’s native wild dog, the dingo (Canis dingo), is threatened by hybridization with feral or domestic dogs. In this study we provide the first comprehensive three dimensional geometric morphometric evaluation of cranial shape for dingoes, dogs and their hybrids. We introduce a novel framework to assess whether modularity facilitates, or constrains, cranial shape change in hybridization. Our results show that hybrid and pure dingo morphology overlaps greatly, meaning that hybrids cannot be reliably distinguished from dingoes on the basis of cranial metrics. We find that dingo morphology is resistant, with observed hybrids exhibiting morphology closer to the dingo than to the parent group dog. We also find that that hybridization with dog breeds does not push the dingo cranial morphology towards the wolf phenotype. Disparity and integration analyses on the ten recovered modules provided empirical support for modularity facilitating shape change over short evolutionary time scales. However, our results show that this is may not be the case in hybridization events, which were not influenced by module integration or disparity levels. We conclude that although hybridization events may introduce breed dog DNA to the dingo population, the native cranial morphology, and therefore likely the feeding eco-niche, of the dingo population is resistant to change. Our results have implications for conservation and management of dingoes and, more broadly, for the influence of integration patterns over ecological time scales in relation to selection pressure.     

转Bt基因抗虫棉的生态风险及治理对策

评述了转Bt基因抗虫棉的生态风险及治理对策。其生态风险主要表现在目标害虫的抗性和对非目标生物群落的变化。目标害虫与转基因抗虫棉的互相作用和抗虫棉杀虫毒素的时空表达方式是目标害虫抗性发展的主要途径。在转基因抗虫棉田中,虽然对目标害虫的防治次数大为减少,但害虫和天敌群落的稳定性仍不如常规棉田,某种次要害虫大发生的可能性较大。认为将转基因抗虫棉纳入综合防治体系并培育更加高效的抗虫棉是治理目标害虫抗性和防止次要害虫上升的重要措施。     

Peak hour in the bush: linear anthropogenic clearings funnel predator and prey species

Linear clearings, such as roads and tracks, are an obvious anthropogenic feature in many remote environments, even where infrastructure is sparse. Predator species have been shown to prefer moving down linear clearings, and therefore, clearings could increase predation risk for other species. We investigated whether tracks cleared for seismic surveys are preferentially used by predators and herbivores in a landscape inhabited by bilbies (Macrotis lagotis), a vulnerable species of conservation concern. We used a paired camera trap array to investigate the use of cleared seismic lines at four time points after clearing (1 month, 3 months, 7 months, 48 months) by six mammal species. Bilbies, cattle (Bos indicus/B. taurus), dingoes (Canis familiaris), feral cats (Felis catus) and agile wallabies (Macropus agilis) preferred to use seismic lines compared with adjacent undisturbed vegetation for almost all surveys, while spectacled hare wallabies (Lagorchestes conspicillatus) avoided them. Bilbies and agile wallabies showed similar temporal activity patterns on and off seismic lines but feral cats, dingoes and cattle used seismic lines at different times of day to control areas. We also investigated microhabitat selection by spool tracking individual bilbies. Bilbies selected a route through vegetation that was more open than surrounding vegetation. While spatial and temporal funnelling of bilbies and their predators (especially cats) may increase the frequency of encounter between the two, it is important to note that bilbies were active at significantly different times to predators both on and off seismic lines. The identified selection for seismic lines, and changes in spatial and temporal overlap between species, can be used to develop effective management strategies, to minimize potential impacts on native species.     

The feeding ecology of the dingo

Summary Changes in the diet of dingoes (Canis familiaris dingo) in response to measured fluctuations of prey populations were followed over 7 years. The study began after great rains had broken a long drought. Eruptions of rodents and rabbits followed, but some prey were always either relatively abundant (live cattle) or scarce (red kangaroo, lizards, birds). Cattle carcasses were increasingly available during a subsequent drought. Small and medium-sized prey, rodents (26%), lizards (12%) and rabbits (56%) were preferred, probably because they were easily caught. Only rabbits were caten consistently regardless of density. By contrast, large prey were eaten in relatively large amounts only during drought, with initial emphasis on red kangaroos (15% overall) and then cattle (17%) mostly as carcasses. The diet was functionally related to the respective abundances of all major prey species, but the relationship shifted during drought when predation on low populations was most severe. There was evidence that growth of resurging prey populations were suppressed by predation. Diets of dingoes did not differ significantly with age or sex. An hypothesis of alternation of predation is presented: dingoes feed sequentially on prey of increasing size (rodents, rabbits, red kangaroos, cattle) in response to rainy periods and subsequent droughts, meanwhile always concentrating on the staple prey (rabbits). The fluctuating abundances of small and medium-sized prey determined not only their own relative availabilities but also that of large prey, and hence determined the diet of the dingo at any time. Prey availability (catchability, accessability) appeared to be more important than prey abundance (numbers, biomass), and the dingo's flexible social organisation allowed versatility in hunting strategies and defence of resources. We conclude that dingoes do not always forage most efficiently as optimal foraging models predict because of the constraints imposed by the capricious environment in arid Australis, where prey availability fluctuates greatly and becomes limited and clumped in drought, so that dingoes may be faced with outright starvation. Instead we conclude that dingoes utilise a conservative feeding strategy and adopt any behaviour which provides at least a threshold quantity of energy or nutrient as part of a trade-off with other competing ecological requirements.     

Predicting the unexpected: using a qualitative model of a New Zealand dryland ecosystem to anticipate pest management outcomes

Pest management is expensive and there is often uncertainty about the benefits for the resources being protected. There can also be unintended consequences for other parts of the ecosystem, especially in complex food webs. In making decisions managers generally have to rely on qualitative information collected in a piecemeal fashion. A method to assist decision making is a qualitative modelling approach using fuzzy cognitive maps, a directed graphical model related to neural networks that can take account of interactions between pests and conservation assets in complex food webs. Using all available information on relationships between native and exotic resources and consumers, we generated hypotheses about potential consequences of single‐species and multi‐species pest control on the long‐term equilibrium abundances of other biotic components of an ecosystem. We applied the model to a dryland ecosystem in New Zealand because we had good information on its trophic structure, but the information on the strength of species interactions was imprecise. Our model suggested that pest control is unlikely to significantly boost native invertebrates and lizards in this ecosystem, suggesting that other forms of management may be required for these groups. Most of the pest control regimes tested resulted in greater abundances of at least one other pest species, which could potentially lead to other management problems. Some of the predictions were unexpected, such as more birds resulting from possum and mouse control. We also modelled the effects of an increase in invasive rabbits, which led to unexpected declines of stoats, weasels, mice and possums. These unexpected outcomes resulted from complex indirect pathways in the food web. Fuzzy cognitive maps allow rapid construction of prototype models of complex food webs using a wide range of data and expert opinion. Their utility lies in providing direction for future monitoring efforts and generating hypotheses that can be tested with field experiments.     

Apex predator suppression is linked to restructuring of ecosystems via multiple ecological pathways

Removal of apex predators can drive ecological regime shifts owing to compensatory positive and negative population level responses by organisms at lower trophic levels. Despite evidence that apex predators can influence ecosystems though multiple ecological pathways, most studies investigating apex predators’ effects on ecosystems have considered just one pathway in isolation. Here, we provide evidence that lethal control of an apex predator, the dingo Canis dingo, drives shifts in the structure of Australia's tropical‐savannah ecosystems. We compared mammal assemblages and understorey structure at seven paired‐sites. Each site comprised an area where people poisoned dingoes and an area without dingo control. The effects of dingo control on mammals scaled with body size. Where dingoes were poisoned, we found greater activity of herbivorous macropods and feral cats, a mesopredator, but sparser understorey vegetation and lower abundances of native rodents. Our study suggests that ecological cascades arising from apex predators’ suppressive effects on herbivores and mesopredators occur simultaneously. Concordant effects of dingo removal across tropical‐savannah, forest and desert biomes suggest that dingoes once exerted ubiquitous top–down effects across Australia and provides support for calls that top–down forcing should be considered a fundamental process governing ecosystem structure.     

Death by sex in an Australian icon: a continent‐wide survey reveals extensive hybridization between dingoes and domestic dogs

Hybridization between domesticated animals and their wild counterparts can disrupt adaptive gene combinations, reduce genetic diversity, extinguish wild populations and change ecosystem function. The dingo is a free‐ranging dog that is an iconic apex predator and distributed throughout most of mainland Australia. Dingoes readily hybridize with domestic dogs, and in many Australian jurisdictions, distinct management strategies are dictated by hybrid status. Yet, the magnitude and spatial extent of domestic dog–dingo hybridization is poorly characterized. To address this, we performed a continent‐wide analysis of hybridization throughout Australia based on 24 locus microsatellite DNA genotypes from 3637 free‐ranging dogs. Although 46% of all free‐ranging dogs were classified as pure dingoes, all regions exhibited some hybridization, and the magnitude varied substantially. The southeast of Australia was highly admixed, with 99% of animals being hybrids or feral domestic dogs, whereas only 13% of the animals from remote central Australia were hybrids. Almost all free‐ranging dogs had some dingo ancestry, indicating that domestic dogs could have poor survivorship in nonurban Australian environments. Overall, wild pure dingoes remain the dominant predator over most of Australia, but the speed and extent to which hybridization has occurred in the approximately 220 years since the first introduction of domestic dogs indicate that the process may soon threaten the persistence of pure dingoes.     

我国害鼠不育控制研究进展

害鼠给人类带来巨大的经济损失,导致严重的生态问题。人们采用各种方法防治鼠害,其中不育控制是一种新的方法。不育控制即通过某种手段使雄性或和雌性绝育,或阻碍胚胎着床,甚至阻断幼体生长,以降低生育率。不育控制的概念最早在20世纪60年代提出,近年来,我国在利用不育技术控制害鼠方面做了大量研究,总结了国内该领域研究的部分结果。在实验室测试了多种不育剂。被测试的不育剂对相应的鼠类几乎都有不育作用;一些不育剂会影响鼠类的行为,这会减弱竞争性繁殖干扰的作用;一些不育剂在达到一定剂量后有致死作用,不育和灭杀的双重作用会产生更好的控制效果;还观察到不育个体的复孕现象,这会减弱控制效果;关于不育剂安全性的研究发现更昔洛韦和M001雄性不育灭鼠剂对家鸽没有任何毒性作用。大量野外实验证实不育剂对害鼠大都有较好的控制效果,实际控制中,控制面积不宜太小。利用数学模型所作的理论分析表明不育控制有不比灭杀控制差的效果;在决定种群是否灭绝上,不育率、灭杀率、选择性收获率等的作用是相同的。根据研究的实际情况,本文提出了一些今后研究中应注意的问题。无论在实验室还是野外,除了种群动态外,还要记录更详细的数据,以期对不育控制有更详细的了解。要加大不育剂对非靶向动物和环境影响的研究。在不育控制这种干扰下,害鼠种群的变化必然导致与其相关的种群也作出相应的变化,这一方面的研究需要进行。每种控制方式都有自己的特点,多种控制方法联合使用会达到更理想的效果。竞争性繁殖干扰现象是存在的,它使种群规模更小,在数学模型中,应体现出这一因素。     

Spatially-explicit wildlife surveillance to prove freedom from diseases or pests

Surveillance undertaken to prove freedom from a disease has traditionally focussed on sampling a specified proportion of the population to determine the presence of the infective agent. Based on a sample of individuals testing negative for disease, standard probability theory using the binomial or hypergeometric distribution can be used to make inference about the probability of disease being absent. However, if the disease agent involves a wildlife host, then determining what proportion of the population was sampled becomes problematic as it requires an estimate of population abundance, which may be difficult and expensive to obtain. Surveillance during the eradication of pests such as feral ungulates often make use of the Judas technique, whereby radio-collared individuals are released and followed in the hope that the sociality of the individuals will betray the locations of conspecifics, which can then be dispatched. Data collected during such surveillance is explicitly spatial, containing information about the ‘search area’ of the Judas animal. However, there has been no attempt to use such data to make inference about the probability of the area being free of the pest, given Judas animals fail to detect any conspecifics. We present a framework for making specific use of the spatial nature of such wildlife surveillance data to make inference about the probability of freedom from the disease or pest. Underlying the sampling framework is a model of the detection process by sampled individuals. Estimates of individual detection probability are spatially smoothed using the extent of individual movements to produce a spatially- explicit detection surface. Bayes theorem is then used to combine this 2-dimensional surface with prior information on the probability of pest or disease presence, prior to sampling, to estimate the probability that the area is free from the disease or pest, given surveillance fails to detect evidence of their presence. We illustrate the method with examples of the detection of bovine Tb in wildlife in New Zealand and the detection of pigs (Sus scrofa) using the Judas technique during the feral pig eradication programme on Santa Cruz Island, California.