Feral cat vs. dingo perception: a gender-cultural bias or a real ecological difference?

Smith, N. (1999). The howl and the pussy: feral cats and wild dogs in the Australian imagination. The Australian journal of anthropology, 10(3): 288-305.

This paper looks at recent attention given to feral cats in Australia, particularly focusing on their symbolic status in eco-nationalist discourses. Australian eco-nationalism is a specific blend of environmentalist and patriotic sentiments which, in an exaggerated way, positions the feral cat as a rapacious European invader predating on native wild life. This vilification of the cat can be related to much earlier forms of (mainly European) symbolism associating the creature with femininity and evil, which I illustrate by looking at the manner in which the feral cat is opposed to the masculinised Australian wild dog—the dingo. I argue that the recent surfacing of this totemic opposition between ‘the howl and the pussycat’ is related to an eco-nationalist sense of place which simultaneously recognises and denies that the human colonisation of Australia was (and is) a form of feral invasion.

Hytten, K. F. (2009). Dingo dualisms: Exploring the ambiguous identity of Australian dingoes. Australian Zoologist, 35(1), 18-27.

How wildlife is defined, and which wildlife is accorded protection, emerges from competing constructions of nature and culture. Few species of Australian wildlife have as ambiguous an identity as dingoes. This paper identifies three dualisms that characterise discourses relating to Australian dingoes Canis lupus dingo. They are at once classified as both a pest and protected species, perceived to be feral and native, and most recently categorised as either pure or hybrid. It is argued that these dualisms are underpinned by different versions of the nature-culture dichotomy. Portrayals and perceptions of dingoes around Australia are explored to reveal how different aspects of the dualisms identified are drawn upon within different contexts. Illustrations of the contradictory constructions of dingoes highlight the need to critically deconstruct discourses relating to wildlife, particularly when they inform actions. As such, this paper demonstrates the important contribution a discourse-sensitive approach can make to understanding human perceptions of wildlife.



Letnic, M., Ritchie, E. G., & Dickman, C. R. (2012). Top predators as biodiversity regulators: the dingo Canis lupus dingo as a case study. Biological reviews, 87(2), 390-413.

Top-order predators often have positive effects on biological diversity owing to their key functional roles in regulating trophic cascades and other ecological processes. Their loss has been identified as a major factor contributing to the decline of biodiversity in both aquatic and terrestrial systems. Consequently, restoring and maintaining the ecological function of top predators is a critical global imperative. Here we review studies of the ecological effects of the dingo Canis lupus dingo, Australia's largest land predator, using this as a case study to explore the influence of a top predator on biodiversity at a continental scale. The dingo was introduced to Australia by people at least 3500 years ago and has an ambiguous status owing to its brief history on the continent, its adverse impacts on livestock production and its role as an ecosystem architect. A large body of research now indicates that dingoes regulate ecological cascades, particularly in arid Australia, and that the removal of dingoes results in an increase in the abundances and impacts of herbivores and invasive mesopredators, most notably the red fox Vulpes vulpes. The loss of dingoes has been linked to widespread losses of small and medium-sized native mammals, the depletion of plant biomass due to the effects of irrupting herbivore populations and increased predation rates by red foxes. We outline a suite of conceptual models to describe the effects of dingoes on vertebrate populations across different Australian environments. Finally, we discuss key issues that require consideration or warrant research before the ecological effects of dingoes can be incorporated formally into biodiversity conservation programs.

Feral cats and dogs among the most abundant IAS in South African National Parks

Spear, D., Foxcroft, L. C., Bezuidenhout, H., & McGeoch, M. A. (2013). Human population density explains alien species richness in protected areas. Biological Conservation, 159: 137-147.

Understanding the drivers of biological invasions, across taxa and regions, is important for designing appropriate management interventions. However there has been no work that has examined potential drivers of both plant and animal invasions, for both species considered to be aliens and those that are invasive. We use South Africa’s national park system (19 national parks, throughout South Africa and covering ∼39,000 km²  as a model to test the generality of predictors of alien species richness in protected areas. We also compare the predictors of alien versus invasive species richness, and alien plant versus alien animal species richness. Species were classified as alien, invasive (having known negative impact on biodiversity) or extralimital, using standard definitions. Potential predictors (numbers of years since the park was proclaimed and since new land was acquired, park area, data availability, human population density in the vicinity of the park, number of roads, number of rivers, indigenous plant species richness and normalised difference vegetation index) of the number of alien and invasive species in national parks were examined for plants and animals using generalised linear models. Human population density surrounding parks was a significant and strong predictor of numbers of alien and invasive species across plants and animals. The role of other predictors, such as NDVI and park age, was inconsistent across models. Human population density has emerged here as an important predictor of alien species richness in protected areas across taxa, providing a basis for guidelines on where to focus surveillance and eradication efforts.

Hissing tits prevent feral cats' predation

Krams, I., J. Vrublevska, K. Koosa, T. Krama, P. Mierauskas, M.J. Rantala & V. Tilgar. 2013. Hissing calls improve survival in incubating female great tits. Acta Oecologica. DOI 10.1007/s10211-013-0163-3

Nest predation is among the most important selective pressure shaping nest-site selection and nest defense behavior in many avian species. In this study, we tested whether the production of one such nest defense behavior—hissing calls—may improve survival of incubating female great tits (Parus major). We found that 72.5 % of incubating females gave hissing calls when they were exposed to a stuffed woodpecker in their nest boxes. The repeatability of the number of hissing calls given was high, as was the latency to give the call. Additionally, natural nest predators attacked hissing and nonhissing females equally often. However, hissing females survived better than silent females. We tested responses of feral cats to playbacks of hissing call during their attacks of nest boxes and found that hissing calls prevented the predator attacks. Taken together, our findings indicate that hissing calls can deter predator attacks and potentially increase survival rates of nesting great tits or their offspring, or both. The propensity to give hissing calls may be related to personality type of incubating female great tits, which needs to be tested experimentally.

Feral cat home range and habitat selection in central Australia

Edwards, G. P., De Preu, N., Shakeshaft, B. J., Crealy, I. V., & Paltridge, R. M. (2001). Home range and movements of male feral cats (Felis catus) in a semiarid woodland environment in central Australia. Austral Ecology, 26(1), 93-101.

There is a paucity of data on the movement patterns of feral cats in Australia. Such data can be used to refine control strategies and improve track-based methods of monitoring populations of feral cats. In this study the home ranges and movements of male feral cats were examined over 3.5 years in a semiarid woodland environment in central Australia. Two home range estimators were used in the examination: (i) minimum convex polygon (MCP); and (ii) fixed kernel. The most widely used method of estimating home range in feral cats is MCP, while the fixed kernel method can be used to identify core areas within a home range. On the basis of the MCP method, the long-term home ranges of feral cats in central Australia were much larger than those recorded elsewhere (mean, 2210.5 ha). Twenty-four hour home ranges were much smaller (mean, 249.7 ha) and feral cats periodically shifted their 24 h ranges within the bounds of their long-term home ranges. Core area analysis indicated marked heterogeneity of space use by male feral cats. Several instances where feral cats moved large distances (up to 34 km) were recorded. These long distance movements may have been caused by nutritional stress. Using data from the literature, it is shown that prey availability is a primary determinant of long-term home range size in feral cats. The relevance of the results to the design of management strategies for feral cats in central Australia is also discussed.

Edwards, G. P., Preu, N., Crealy, I. V., & Shakeshaft, B. J. (2002). Habitat selection by feral cats and dingoes in a semi‐arid woodland environment in central Australia. Austral Ecology, 27(1), 26-31.

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.

Managing impacts of cats in peri-urban reserves

McCarthy, S. (2005). Managing impacts of domestic cats in peri-urban reserves. In Proceedings of the Fourteenth National Conference on Urban Animal Management in Australia.(Australian Veterinary Committee: Canberra.) Available at http://www. uam. net. au/Publications/

Impacts of domestic cats in peri-urban reserves may occur directly through predation, indirectly through disease transmission, by competition with native species and by supplementation of the feral cat population. Predation, in particular, has been the subject of increasing community concern and scientific research in the last decade which has resulted in increased pressure on local government to develop domestic cat control strategies. This literature review discusses domestic cat impacts in peri-urban reserves and management strategies for their control.

TNR ineffective in controlling cat colonies

Castillo, D. and Clarke, A.L. 2003. Trap/neuter/release methods ineffective in controlling domestic cat "colonies" on public lands. Natural Areas Journal. 23 (3): 247-253. 

Domestic cat (Felis catus L.) advocates have formed coalitions whose goals are to promote the welfare of cats through the use of a specific nonlethal population control method. This method consists of trapping, neutering. and releasing cats into supervised cat colonies located on private and public lands, including state and county parks and natural areas. Advocates believe that this method will help reduce the number of unwanted cats and stabilize the population of unwanted cats over time. Furthermore, advocates claim that established colonies are temporary in nature and will decrease in size over time through death and adoption. This claim was tested through photographic and observational capture-recapture technique.~ in Miami-Dade County, Florida, USA, in two Metro-Dade County parks (A. D. Barnes Park and Crandon Marina). Although the number of original colony members decreased over time, illegal dumping of unwanted cats and the attraction of stray cats to provisioned food offset reductions in cat numbers caused by death and adoption. Furthermore, overall population size of the colony at A. D. Barnes Park increased over time, and at Crandon Marina neither decreased nor increased over time. Our study suggests that this method is not an effective means to control the population of unwanted cats and confirms that the establishment of cat colonies on public lands encourages illegal dumping and creates an attractive nuisance. We recommend that advocates of cat colonies seek a longterm solution to the pet overpopulation issue by redirecting their efforts toward the underlying problem of managing irresponsible pet owners.

Cats' spatial interference with coyotes

Gehrt SD, Wilson EC, Brown JL, Anchor C (2013) Population Ecology of Free-Roaming Cats and Interference Competition by Coyotes in Urban Parks. PLoS ONE 8(9)

Free-roaming cats are a common element of urban landscapes worldwide, often causing controversy regarding their impacts on ecological systems and public health. We monitored cats within natural habitat fragments in the Chicago metropolitan area to characterize population demographics, disease prevalence, movement patterns and habitat selection, in addition to assessing the possible influence of coyotes on cats. The population was dominated by adults of both sexes, and 24% of adults were in reproductive condition. Annual survival rate was relatively high (S=0.70, SE=0.10), with vehicles and predation the primary causes of death. Size of annual home range varied by sex, but not reproductive status or body weight. We observed partitioning of the landscape by cats and coyotes, with little interspecific overlap between core areas of activity. Coyotes selected for natural habitats whereas cats selected for developed areas such as residences. Free-roaming cats were in better condition than we predicted, but their use of natural habitat fragments, and presumably their ecological impact, appeared to be limited by coyotes through intraguild competition.

Predator-prey : cats-rabbits

Cruz, J., Glen, A. S., & Pech, R. P. (2013). Modelling Landscape-Level Numerical Responses of Predators to Prey: The Case of Cats and Rabbits. PLoS ONE, 8(9).

Predator-prey systems can extend over large geographical areas but empirical modelling of predator-prey dynamics has been largely limited to localised scales. This is due partly to difficulties in estimating predator and prey abundances over large areas. Collection of data at suitably large scales has been a major problem in previous studies of European rabbits (Oryctolagus cuniculus) and their predators. This applies in Western Europe, where conserving rabbits and predators such as Iberian lynx (Lynx pardinus) is important, and in other parts of the world where rabbits are an invasive species supporting populations of introduced, and sometimes native, predators. In pastoral regions of New Zealand, rabbits are the primary prey of feral cats (Felis catus) that threaten native fauna. We estimate the seasonal numerical response of cats to fluctuations in rabbit numbers in grassland–shrubland habitat across the Otago and Mackenzie regions of the South Island of New Zealand. We use spotlight counts over 1645 km of transects to estimate rabbit and cat abundances with a novel modelling approach that accounts simultaneously for environmental stochasticity, density dependence and varying detection probability. Our model suggests that cat abundance is related consistently to rabbit abundance in spring and summer, possibly through increased rabbit numbers improving the fecundity and juvenile survival of cats. Maintaining rabbits at low abundance should therefore suppress cat numbers, relieving predation pressure on native prey. Our approach provided estimates of the abundance of cats and rabbits over a large geographical area. This was made possible by repeated sampling within each season, which allows estimation of detection probabilities. A similar approach could be applied to predator-prey systems elsewhere, and could be adapted to any method of direct observation in which there is no double-counting of individuals. Reliable estimates of numerical responses are essential for managing both invasive and threatened predators and prey.

Breeding of Procellariidae before and after eradication of feral cats at Marion Island

Cooper, J. Marais, A.V.N., Bloomer, J.P. & Bester, M.N. 1995. A success story: breeding of burrowing petrels (Procellariidae) before and after eradication of feral cats Felis catus at sub-Antarctic Marion Island. Marine Ornithology 23: 33-37.

Greatwinged Petrels Pterodroma macroptera and Blue Petrels, Halobaena caerulea bred more successfully alter the eradication in 1991 of feral domestic cats Felis catus at subantarctic Marion Island. The larger Whitechinned Petrel Procellaria aequinoctialis did not show such improvement, although percentage burrow occupancy in the late breeding season increased significantly between 1982/83 and 1988/89 for that species, suggesting decreased cat predation during this period of cat control. Breeding success and burrow density of selected species of burrowing petrels should be monitored to ascertain the rate of recovery of their populations now that Marion Island is cat-free. 

Domestic cat introgression in wildcat in Iberia

Oliveira, R., Godinho, R., Randi, E., Ferrand, N., & Alves, P. C. (2008). Molecular analysis of hybridisation between wild and domestic cats (Felis silvestris) in Portugal: implications for conservation. Conservation Genetics, 9(1): 1-11.

The endangered European wildcat (Felis silvestris silvestris) is represented, today, by fragmented and declining populations whose genetic integrity is considered to be seriously threatened by crossbreeding with widespread free-ranging domestic cats. Extensive and recent hybridisation has been described in Hungary and Scotland, in contrast with rare introgression of domestic alleles in Italy and Germany. In Portugal, the wildcat is now listed as VULNERABLE in the Red Book of Portuguese Vertebrates. Nevertheless, genetic diversity of populations and the eventual interbreeding with domestic cats remain poorly studied. We surveyed genetic variation at 12 autosomal microsatellites for 34 wild and 64 domestic cats collected across Portugal. Wild and domestic cats were significantly differentiated both at allele frequencies and sizes (F _ST=0.11, R _ST = 0.18, P < 0.001). Population structure and admixture analyses performed using Bayesian approaches also showed evidence of two discrete groups clustering wild and domestic populations. Results did not show significant genetic divergence among Northern, Central and Southern wildcats. Six morphologically identified wildcats were significantly assigned to the domestic cluster, revealing some discrepancy between phenotypic and genetic identifications. We detected four hybrids (approximately 14%) using a consensus analysis of different Bayesian model-based software. These hybrids were identified throughout all sampled areas, suggesting that hybridisation is of major concern for the appropriate implementation of wildcat conservation strategies in Portugal.

Oliveira, R., Godinho, R., Randi, E., & Alves, P. C. (2008). Hybridization versus conservation: are domestic cats threatening the genetic integrity of wildcats (Felis silvestris silvestris) in Iberian Peninsula?  Philosophical Transactions of the Royal Society B: Biological Sciences, 363(1505), 2953-2961.

Cross-breeding between wild and free-ranging domestic species is one of the main conservation problems for some threatened species. The situation of wildcats (Felis silvestris silvestris) in Europe is a good example of this critical phenomenon. Extensive hybridization was described in Hungary and Scotland, contrasting with occasional interbreeding in Italy and Germany. First analyses in Portugal revealed a clear genetic differentiation between wild and domestic cats; however, four hybrids were detected. Here, we extended the approach to Iberian Peninsula using multivariate and Bayesian analyses of multilocus genotypes for 44 Portuguese wildcats, 31 Spanish wildcats and 109 domestic cats. Globally, wild and domestic cats were significantly differentiated (F _ST=0.20, p<0.001) and clustered into two discrete groups. Diverse clustering methods and assignment criteria identified an additional hybrid in Portugal, performing a total of five admixed individuals. The power of admixture analyses was assessed by simulating hybrid genotypes, which revealed that used microsatellites were able to detect 100, 91 and 85% of first-generation hybrids, second-generation genotypes and backcrosses, respectively. These findings suggest that the true proportion of admixture can be higher than the value estimated in this study and that the improvement of genetic tools for hybrids detection is crucial for wildcat conservation.


See more on domestic cat introgression in wildcat

Controlling cats through the control of rabbits

Courchamp, F., Langlais, M., & Sugihara, G. (1999). Control of rabbits to protect island birds from cat predation. Biological Conservation, 89(2), 219-225.

Both introduced predators (e.g. domestic cats) and introduced small grazers (e.g. rabbits) are harmful to many island vertebrate species. The effects of cats on indigenous species are direct (predation), whereas the most obvious effects of rabbits are often indirect and in the longer term. Thus, in situations where both cats and rabbits are present, priority is frequently given to control of cats. However, the presence of rabbits can allow an increased predator population which can lead to extinction of the indigenous and less well adapted prey species, and increase the difficulty of predator control. Through a mathematical model, we show that control of introduced prey facilitates the control of the introduced predator population. Moreover, predator control may fail to protect the indigenous prey if control of the introduced prey is not undertaken simultaneously. Therefore, control of both introduced species is the best strategy.

Pathogens in Brazilian wild canids and domestic dogs

Curi, N. H. A., Araújo, A. S., Campos, F.S., Lobato, Z. I. P., Gennari, S. M., Marvulo, M. F. V., Silva, J. C. R. & Talamoni,S A. 2010. Wild canids, domestic dogs and their pathogens in Southeast Brazil: disease threats for canid conservation. Biodiversity and Conservation 19: 3513-3524.

Wild canids are under many pressures, including habitat loss, fragmentation and disease. The current lack of information on the status of wildlife health may hamper conservation efforts in Brazil. In this paper, we examined the prevalence of canine pathogens in 21 free-ranging wild canids, comprising 12 Cerdocyon thous (crab-eating fox), 7 Chrysocyon brachyurus (maned wolf), 2 Lycalopex vetulus (hoary fox), and 70 non-vaccinated domestic dogs from the Serra do Cipó National Park area, Southeast Brazil. For wild canids, seroprevalence of antibodies to canine parvovirus, canine adenovirus, canine coronavirus and Toxoplasma gondii was 100 (21/21), 33 (7/21), 5 (1/19) and 68 (13/19) percent, respectively. Antibodies against canine distemper virus, Neospora caninum or Babesia spp. were not found. We tested domestic dogs for antibodies to canine parvovirus, canine distemper virus and Babesia spp., and seroprevalences were 59 (41/70), 66 (46/70), and 42 (40/70) percent, respectively, with significantly higher prevalence in domestic dogs for CDV (P < 0.001) and Babesia spp. (P = 0.002), and in wild canids for CPV (P < 0.001). We report for the first time evidence of exposure to canine coronavirus in wild hoary foxes, and Platynossomun sp. infection in wild maned wolves. Maned wolves are more exposed to helminths than crab-eating foxes, with a higher prevalence of Trichuridae and Ancylostomidae in the area. The most common ectoparasites were Amblyomma cajennense, A. tigrinum, and Pulex irritans. Such data is useful information on infectious diseases of Brazilian wild canids, revealing pathogens as a threat to wild canids in the area. Control measures are discussed.

Dog pathogens in threatened wild canids

Deem, Sharon L., & Louise H. Emmons. 2005. Exposure of free-ranging maned wolves (Chrysocyon brachyurus) to infectious and parasitic disease agents in the Noel Kempff Mercado National Park, Bolivia. Journal of zoo and wildlife medicine 36 (2): 192-197.

Maned wolves (Chrysocyon brachyurus) are neotropic mammals, listed as a CITES Appendix II species, with a distribution south of the Amazon forest from Bolivia, through northern Argentina and Paraguay and into eastern Brazil and northern Uruguay. Primary threats to the survival of free-ranging maned wolves include habitat loss, road kills, and shooting by farmers. An additional threat to the conservation of maned wolves is the risk of morbidity and mortality due to infectious and parasitic diseases. Captive maned wolves are susceptible to, and die from, common infectious diseases of domestic dogs (Canis familiaris) including canine distemper virus (CDV), canine parvovirus (CPV), rabies virus, and canine adenovirus (CAV). Results from this study show that free-ranging maned wolves in a remote area of Bolivia have been exposed to multiple infectious and parasitic agents of domestic carnivores, including CAV, CDV, CPV, canine coronavirus, rabies virus, Leptospira interrogans spp., Toxoplasma gondii, and Dirofilaria immitis, and may be at increased risk for disease due to these agents.

Nonsurgical fertility control for managing free-roaming dog

Massei, G., & Miller, L. A. (2013). Nonsurgical fertility control for managing free-roaming dog populations: A review of products and criteria for field applications.Theriogenology.

About 75% of dogs worldwide are free to roam and reproduce, thus creating locally overabundant populations. Problems caused by roaming dogs include diseases transmitted to livestock and humans, predation on livestock, attacks on humans, road traffic accidents, and nuisance behavior. Nonsurgical fertility control is increasingly advocated as more cost-effective than surgical sterilization to manage dog populations and their impact. The aims of this review were to 1) analyze trends in numbers of scientific publications on nonsurgical fertility control for dogs; 2) illustrate the spectrum of fertility inhibitors available for dogs; 3) examine how differences between confined and free-roaming dogs might affect the choice of fertility inhibitors to be used in dog population management; and 4) provide a framework of criteria to guide decisions regarding the use of nonsurgical fertility control for dog population management. The results showed that the 117 articles published between 1982 and 2011 focussed on long-term hormonal contraceptives, such as gonadotropin-releasing hormone agonists, immunocontraceptives, and male chemical sterilants. The number of articles published biennially increased from one to five papers produced in the early 1980s to 10 to 20 in the past decade. Differences between confined dogs and free-roaming dogs include reproduction and survival as well as social expectations regarding the duration of infertility, the costs of sterilization, and the responsibilities for meeting these costs. These differences are likely to dictate which fertility inhibitors will be used for confined or free-roaming dogs. The criteria regarding the use of fertility control for dog population management, presented as a decision tree, covered social acceptance, animal welfare, effectiveness, legal compliance, feasibility, and sustainability. The review concluded that the main challenges for the future are evaluating the feasibility, effectiveness, sustainability, and effects of mass nonsurgical sterilization campaigns on dog population size and impact as well as integrating nonsurgical fertility control with disease vaccination and public education programs.

Cat eradication decreases shearwater mortality

Keitt, B.S. & Tershy, B.R. (2003) Cat eradication significantly decreases shearwater mortality. Animal Conservation, 6, 307-308

Introduced predators are a leading threat to seabird populations world-wide and cats (Felis catus) have probably had the most universally damaging effect (Moors & Atkinson, 1984). Eradication of feral cat populations from seabird colonies is a conservation priority (Tershy et al., 2002) and there are many studies that demonstrate the benefits of these actions for seabirds (e.g. Forsell, 1982; Cooper et al., 1995). However, detailed estimates of the effects of cat predation on seabird population viability are lacking in spite of the fact that such data could provide important support for land managers attempting to promote eradication programmes for seabird restoration.

See also in Conservation Evidence

Vulture awareness day

On the International Vulture Awareness Day, it's worth to mention the impact of feral and stray dogs on vultures arround the world, outcompiting and even predating on them.

Impact of cats and foxes on the small vertebrate fauna in Western Australia

Short, J., Calver, M. C., & Risbey, D. A. (1999). The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. I. Exploring potential impact using diet analysis. Wildlife Research, 26(5), 621-630.

The diets of cats (Felis catus) and foxes (Vulpes vulpes) killed during predator control at a semi-arid site in Western Australia were studied to see which prey species may be affected by predation from these introduced predators. The number of items, biomass and frequency of occurrence of each food type in the gut contents from 109 fetal cats, 62 semi-feral cats and 47 foxes were used to calculate an Index of Relative Importance for each food category for each predator. Mammals were the most important prey group for all three predators, with rabbit being the most highly ranked prey species. The diets of feral and semi-feral cats were similar in dietary diversity but differed in the frequency of occurrence of some food categories. Native rodents, birds and reptiles occurred more frequently and were ranked higher in the diet of feral cats, and food scraps occurred more frequently in the diet of semi-feral cats. The diet of foxes was less diverse than that of either group of cats. Invertebrates and sheep carrion were more important prey categories for foxes than for cats. In the summer-autumn period, foxes ate more sheep carrion and invertebrates than they did in winter-spring. The diet of feral cats was more diverse in summer-autumn, including a greater range of invertebrates and more rodents, birds and reptiles than in the winter-spring period. We predict that cats are more likely to have an impact on small vertebrates at this site and that the control of cats could lead to recoveries in the populations of native rodents, birds and reptiles. By contrast, the control of foxes alone may lead to a rise in cat numbers and a consequent detrimental impact on small vertebrate populations.


Risbey, D. A., Calver, M. C., Short, J., Bradley, J. S., & Wright, I. W. (2000). The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. II. A field experiment. Wildlife Research, 27(3), 223-235.

The hypothesis that predation by feral cats and introduced foxes reduces population sizes of small, native vertebrates was supported by results of a predator-removal experiment at Heirisson Prong, a semi-arid site in Western Australia. The methods of control used against cats and foxes to protect native mammals reintroduced to Heirisson Prong produced three broad ‘predator zones’: a low-cat and low-fox zone, where foxes were eradicated and spotlight counts of cats declined after intensive cat control; a high-cat and low-fox zone where spotlight counts of cats increased three-fold after foxes were controlled; and a zone where numbers of cats and foxes were not manipulated. Small mammals and reptiles were monitored for one year before and three years after predator control began. Captures of small mammals increased in the low-cat and low-fox zone, but where only foxes were controlled captures of small mammals declined by 80%. In the absence of cat and fox control, captures of small mammals were variable over the sampling period, lower than where both cats and foxes were controlled, yet higher than where only foxes were controlled. The capture success of reptiles did not appear to be related to changes in predator counts. This study presents the first experimental evidence from mainland Australia that feral cats can have a negative impact on populations of small mammals.

Teaching the impact of introduced predators

Calver, M. C., King, D. R., & Short, J. (1998). Ecological blunders and conservation: the impact of introduced foxes and cats on Australian native fauna. Journal of Biological Education, 32(1), 67-72.

Many vertebrate extinctions followed the introduction of the exotic predators, the fox and the cat, to Australia. While experiments have confirmed the case against the fox as a serious threat to endangered species, there are no direct experimental links showing recovery of prey populations following culling of cat numbers. This, coupled with the emotional attachment of many people to cats, has led to some opposition to their control, especially when limitations on the freedom of pets to roam are proposed. The introduced predator case is a stimulating example for teaching aspects of the emerging discipline of conservation biology and highlights the interplay of bioethics, public opinion, and biological principles in conservation decision-making. Suggested classroom exercises allow students to compare and contrast experimental and non-experimental approaches to assessing predator impact, consider ethical issues in controlling predators for conservation, and reach their own conclusions on the impact of cats on local wildlife.

Pet cats reduce effective protected area

Lilith, M., Calver, M.C. and Garkaklis, M.J. (2008) Roaming habits of pet cats on the suburban fringe in Perth, Western Australia: What size buffer zone is needed to protect wildlife in reserves? In: Lunney, D., Munn, A. and Meikle, W., (eds.) Too close for comfort : contentious issues in human-wildlife encounters. Royal Zoological Society of New South Wales, Mosman, NSW, pp. 65-72.

We radiotracked 18 pet cats Felis catus from rural and urban areas within the City of Armadale, Western Australia, both at night and during the day between August 2003 and February 2005 to estimate the size of buffer zone required to reduce incursions by pet cats into native bushland. Home ranges of rural cats ranged from 0.07ha to 2.86ha, while those of urban cats were 0.01 ha to 0.64ha. Male and female cats had similar home ranges and there was no evidence of seasonal differences in home ranges.The longest linear distance moved by any cat was 300m, so allowing a 20% margin for estimation error a buffer zone of 360m is needed to reduce incursions by pet cats into native bushland in this municipality.

Impact of stray dogs and cats on the community in the Caribbean

Trotman, M. (n.d.). Regional realities: Impact of stray dogs and cats on the community: Impact on economy, including tourism: Impact on livestock, wildlife and the environment.

The welfare concerns surrounding stray and roaming dogs and cats are well understood, however the impact that these animals have on Caribbean societies is often not fully appreciated, nor as far as I know, have the economic losses been quantified. Losses in terms of the cost of health care and veterinary care, losses to the agriculture industry, indirect losses to the tourist industry and of course the environmental costs. It is important that when designing animal control and animal welfare programmes for Caribbean Islands, the unique circumstances (social, cultural, environmental and economic) that exist in each territory be taken into account.

Gradient of habitat use of mammals

Goad, E. H. (2013). Mammalian habitat use along a residential development gradient in Northern Colorado (Doctoral dissertation, Colorado State University).

“Exurban” development occupies nearly five times more land in the United States than urban and suburban development combined. Understanding the effects of exurban development on biodiversity thus has important and wide-ranging implications for the planning, construction and stewardship of sustainable communities and surrounding rural lands. To assess the impact of exurban development on mammalian habitat use, wildlife cameras were placed along a unique development gradient designed to capture landscape permeability in a rapidly growing rural region of Colorado. Multiple-season species occupancy and relative activity (frequency of detections) were measured in summer and winter seasons and these data were analyzed in conjunction with a novel, acoustic-based approach to assessing human activity. Impacts of exurban housing varied by mammal species, with some species, such as bobcats, elk, and coyotes, showing decreased activity and occupancy levels at higher housing densities, whereas others, including red foxes and Abert’s squirrels, occurred more frequently in these areas. Human-sourced activities associated with development and non-natural sound levels emerged as top models for most species. Relative activity rates corroborated occupancy results, indicating that some species not only use habitat in high density areas, they use it more frequently. In addition, some species, including black bears, preferentially used embedded reenbelts in highdensity exurban subdivisions, suggesting that greenbelts may be important for structural and functional connectivity. This study demonstrates that the impacts of exurban development are species–dependent. However, incorporating well-designed and naturally vegetated open spaces into development projects and minimizing human disturbance may be critical to mitigating development impacts to most wildlife in regions undergoing continued exurban expansion.

Effect of exurban growing on vertebrate abundance

Odell, E. A., & Knight, R. L. (2001). Songbird and Medium‐Sized Mammal Communities Associated with Exurban Development in Pitkin County, Colorado. Conservation Biology, 15(4), 1143-1150.

Residential development is occurring at unprecedented rates in the Rocky Mountain region of the United States, with unknown ecological consequences. We conducted our research in exurban development in Pitkin County, Colorado, between May and June in 1998 and 1999. Unlike suburban development, exurban development occurs beyond incorporated city limits, and the surrounding matrix remains the original ecosystem type. We surveyed songbirds and medium-sized mammals at 30, 180, and 330 m away from 40 homes into undeveloped land to examine the effect of houses along a distance gradient, and in developments of two different housing densities as well as undeveloped sites to examine the effect of housing density. We placed bird species into one of two groups for the house-distance effect: (1) human-adapted species, birds that occurred in higher densities close to developments and lower densities farther away and (2) human-sensitive species, birds that occurred in highest densities farthest from homes and in lowest densities close to development. For both groups, densities of individual species were statistically different between the 30- and 180-m sites. Six species were classified as human-adapted, and six were classified as human-sensitive for the house-distance effect. Dogs (Canis familiaris) and house cats ( Felis domesticus) were detected more frequently closer to homes than farther away, and red foxes ( Vulpes vulpes) and coyotes (Canis latrans) were detected more frequently farther away from houses. With respect to the effect of housing density, most avian densities did not differ significantly between high- and low-density development but were statistically different from undeveloped sites. Six species were present in higher densities in developed areas, and eight species were present in higher densities in undeveloped parcels. Similar results were found for mammalian species, with dogs and cats detected more frequently in high-density developments and red foxes and coyotes detected more frequently in undeveloped parcels of land. From an ecological standpoint, it is preferable to cluster houses and leave the undeveloped areas in open space, as opposed to dispersing houses across the entire landscape.

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El desarrollo residencial esta ocurriendo en el oeste de las Montañas Rocallosas a ritmos sin precedente, con consecuencias ecológicas desconocidas. Desarrollamos nuestra investigación en un desarrollo exurbano en el Condado Pitkin, Colorado entre mayo y junio de 1998 y 1999. A diferencia del desarrollo suburbano, el desarrollo exurbano ocurre más allá de los límites de la ciudad y en la matriz que lo rodea permanece el ecosistema original. Registramos aves canoras y mamíferos pequeños a 30, 180 y 330 m de 40 casas en terrenos sin desarrollar para examinar el efecto de las casas a los largo de un gradiente de distancia, y en desarrollos con dos diferentes densidades de casas para examinar el efecto de la densidad. Colocamos a las especies de aves en uno de dos grupos para el efecto casa –distancia 1) especies adaptadas al humano, aves con la mayor densidad cerca de los desarrollos urbanos y menor densidad lejos de ellos y 2) especies sensibles al humano, aves que ocurrían con la mayor densidad lejos de los hogares y menor densidad cerca del desarrollo urbano. Para ambos grupos, las densidades de especies individuales fueron estadísticamente distintas en los sitios entre 30 y 180 m. Seis especies fueron clasificadas como adaptadas al humano y seis fueron clasificadas como especies sensibles al humano para el efecto casa – distancia. Se detectaron perros ( Canis familiaris) y gatos ( Felis domesticus) con mayor frecuencia cerca de las casas que lejos de ellas, y se detectaron zorros rojos ( Vulpes vulpes) y coyotes (Canis latrans) con mayor frecuencia lejos de las casas. Respecto al efecto de la densidad de casas, la mayoría de las densidades de aves no fueron significativamente diferentes entre el desarrollo de alta y baja densidad, pero fueron estadísticamente distintas de los sitios sin desarrollo. Seis especies tuvieron mayor densidad en los sitios desarrollados y ocho especies presentaron mayor densidad en las parcelas no desarrolladas. Se encontraron resultados similares para las especies de mamíferos, detectándose perros y gatos más frecuentemente en desarrollos con alta densidad; mientras que zorros rojos y coyotes fueron detectados más frecuentemente en las parcelas sin desarrollo. Desde una perspectiva ecológica, es preferible agrupar las casas y dejar las áreas sin desarrollo en espacios abiertos, y no dispersar las casas por todo el paisaje.

Pet cats' impact on biodiversity in Australian suburbia

Lilith, M. (2007) Do pet cats (Felis catus) have an impact on species richness and abundance of native mammals in low-density Western Australian suburbia? PhD thesis, Murdoch University.

Cat ownership in Australia is declining compared to an increasing trend of cat ownership in the United Kingdom, United States and Europe. The decline in Australia may be linked to concerns over perceived impacts of cat predation and an associated dislike of cats. However, while there are numerous studies on feral cats and their impacts on declining native fauna, the impact of pet cats on suburban wildlife or fauna in remnant bushland is relatively unknown although there is a wide perception of risk. The primary aim of this thesis was to apply the precautionary principle to the question of the putative impact of pet cats on the abundance and diversity of small mammals in urban bushland adjacent to low-density suburbia in the City of Armadale, a municipality on the south-east fringe of Perth, Western Australia. At the time of writing, Western Australia is yet to introduce state legislation governing cat control although many local councils within the state have either implemented or are in the process of implementing cat regulations.

The precautionary principle was deemed an ideal approach to this question, because it provides a rationale for deciding on possible actions where both the potential risk to environmental values and the uncertainty about possible impacts are high. In such cases the precautionary principle requires two broad lines of action: firstly, detailed consultation with stakeholders to determine their perceptions of risk and the actions they are prepared to take to reduce it and, secondly, research to reduce uncertainty.

With regard to stakeholder consultation, local residents were surveyed in regard to their attitudes and current cat husbandry practices. A substantial proportion of respondents within this municipality believed cat regulations were necessary (75% of owners and 95% of non-owners). At least 70% of both owners and non-owners agreed with the propositions that cats not owned by licensed breeders should be desexed, local councils should restrict the maximum number of cats that can be owned on one property and that pet cats entering nature reserves are harmful to wildlife. Most (c.85%) cat owners agreed that they would license their cats if that became compulsory. Although fewer owners (c.60%) were prepared to keep their cats on their property at all times to protect wildlife, over 80% were willing to confine their cats at night if it was required. Owners seemed to be substantially motivated by the value of these measures in reducing injury to cats and facilitating the return of lost animals rather than concern over wildlife protection.

Attempts to reduce uncertainty involved (i) assessing roaming patterns of pet cats to determine the sizes of appropriate buffer zones around nature reserves, and (ii) determining species diversity, species richness and abundance of small mammals in remnant bushland adjacent to sub-divisions with varying regulations governing cat husbandry. Radio tracking results to assess cat roaming patterns showed substantial variation in home range size between cats in high density suburbia (ranged between 0.01 ha - 0.64 ha) and those in low density suburbia (ranged from 0.07 ha - 2.86ha). Larger home range sizes of cats in the rural areas (up to 2.9 ha) suggest buffer zones of up to 500 metres around nature reserves are needed to exclude almost all roaming cats. The abundance and species richness of small mammals were investigated in four areas of remnant bushland. Two were adjacent to subdivisions where cat ownership was unrestricted, one next to a subdivision where cat ownership was prohibited and the remaining one next to a subdivision where compulsory night curfew and bells on pet cats were enforced. No definitive evidence of predatory impact by pet cats on the small mammals was found. Mammal species diversity was not significantly different between sites and species richness and absolute abundance were not higher in sites where cats were restricted. Vegetation comparisons showed significant differences in the structure and species composition of the vegetation between most sites and the mammal species richness and abundance appeared linked to ground cover density in the various sites. This factor, not cat restrictions, appeared to be the primary determinant of species richness, species diversity and absolute numbers of small mammals in these sites.

This study in the City of Armadale has shown that the implementation of proposed cat legislation must have a 'whole of ecosystem' approach, i.e. protecting identified remnant bushland containing biodiversity from threatening processes such as plant disease and inappropriate fire, especially arson, as well as possible predations from pet cats. Habitat restoration and protection may be more important conservation activities than regulation of cats. Regulation of cats can be done at differing levels of intensity and cost, bearing in mind that this community is receptive to regulation of some aspects of cat ownership. Community education on the values of cat confinement in regards to cat welfare might increase chances of compliance.

Feral cat definition and management strategies

Gosling, L., Stavisky, J., & Dean, R. (2013). What is a feral cat? Variation in definitions may be associated with different management strategies. Journal of feline medicine and surgery, 15(9), 759-764.

Study rationale: The definition of a true feral cat is an area of much contention, with many variations used worldwide. In this study, opinions were gathered from feral cat rescue workers and veterinary surgeons working in the United Kingdom to identify a practical definition of a feral cat, suitable for use in the field, education and research.

Protocol: A mixed methods approach, using questionnaires and focus groups, was used to collect data from feral cat workers and veterinary surgeons.

Findings: Conflicts in opinion on the implications of taming feral cats exist. The rescue workers typically felt that most cats could be tamed, whereas the veterinary surgeons felt this was generally inappropriate, except in the case of young kittens. A consistent definition of feral cats would enable better communication regarding the welfare and management of these animals, and would be useful for further research and education of the public.

Proposed definition: A feral cat is proposed by this study to be a cat that is unapproachable in its free-roaming environment and is capable of surviving with or without direct human intervention, and may additionally show fearful or defensive behaviour on human contact.

Black wolves

Anderson, T. M., Candille, S. I., Musiani, M., Greco, C., Stahler, D. R., Smith, D. W., Padhukasahasram, B., Randi, E., Leonard, J.A., Bustamante, C.D., Ostrander,E.A., Tang, H., Wayne, R.K. & Barsh, G. S. (2009). Molecular and evolutionary history of melanism in North American gray wolves. Science, 323(5919), 1339-1343.

Morphological diversity within closely related species is an essential aspect of evolution and adaptation. Mutations in the Melanocortin 1 receptor (Mc1r) gene contribute to pigmentary diversity in natural populations of fish, birds, and many mammals. However, melanism in the gray wolf, Canis lupus, is caused by a different melanocortin pathway component, the K locus, that encodes a beta-defensin protein that acts as an alternative ligand for Mc1r. We show that the melanistic K locus mutation in North American wolves derives from past hybridization with domestic dogs, has risen to high frequency in forested habitats, and exhibits a molecular signature of positive selection. The same mutation also causes melanism in the coyote, Canis latrans, and in Italian gray wolves, and hence our results demonstrate how traits selected in domesticated species can influence the morphological diversity of their wild relatives.


See more about wild canid hybridisation with dogs

Domestic dogs and SE European wolves

Verginelli, F., Capelli, C., Coia, V., Musiani, M., Falchetti, M., Ottini, L., Palmirotta, R., Tagliacozzo, A., de Grossi Mazzorin, I. & Mariani-Costantini, R. (2005). Mitochondrial DNA from prehistoric canids highlights relationships between dogs and South-East European wolves.Molecular biology and evolution, 22(12), 2541-2551.

The question of the origins of the dog has been much debated. The dog is descended from the wolf that at the end of the last glaciation (the archaeologically hypothesized period of dog domestication) was one of the most widespread among Holarctic mammals. Scenarios provided by genetic studies range from multiple dog-founding events to a single origin in East Asia.
 The earliest fossil dogs, dated ≈17–12,000 radiocarbon (¹⁴C) years ago (YA), were found in Europe and in the Middle East. Ancient DNA (a-DNA) evidence could contribute to the identification of dog-founder wolf populations. To gain insight into the relationships between ancient European wolves and dogs we analyzed a 262-bp mitochondrial DNA control region fragment retrieved from five prehistoric Italian canids ranging in age from ≈15,000 to ≈3,000 ¹⁴C YA. These canids were compared to a worldwide sample of 547 purebred dogs and 341 wolves. The ancient sequences were highly diverse and joined the three major clades of extant dog sequences. Phylogenetic investigations highlighted relationships between the ancient sequences and geographically widespread extant dog matrilines and between the ancient sequences and extant wolf matrilines of mainly East European origin. The results provide a-DNA support for the involvement of European wolves in the origins of the three major dog clades. Genetic data also suggest multiple independent domestication events. East European wolves may still reflect the genetic variation of ancient dog-founder populations.

See also this post

Introduction of dogs in Australia and the Pacific

Savolainen, P., Leitner, T., Wilton, A. N., Matisoo-Smith, E., & Lundeberg, J. (2004). A detailed picture of the origin of the Australian dingo, obtained from the study of mitochondrial DNA. Proceedings of the National Academy of Sciences of the United States of America, 101(33), 12387-12390.

To determine the origin and time of arrival to Australia of the dingo, 582 bp of the mtDNA control region were analyzed in 211 Australian dingoes sampled in all states of Australia, 676 dogs from all continents, and 38 Eurasian wolves, and 263 bp were analyzed in 19 pre-European archaeological dog samples from Polynesia. We found that all mtDNA sequences among dingoes were either identical to or differing by a single substitution from a single mtDNA type, A29. This mtDNA type, which was present in >50% of the dingoes, was found also among domestic dogs, but only in dogs from East Asia and Arctic America, whereas 18 of the 19 other types were unique to dingoes. The mean genetic distance to A29 among the dingo mtDNA sequences indicates an origin ≈5,000 years ago. From these results a detailed scenario of the origin and history of the dingo can be derived: dingoes have an origin from domesticated dogs coming from East Asia, possibly in connection with the Austronesian expansion into Island Southeast Asia. They were introduced from a small population of dogs, possibly at a single occasion, and have since lived isolated from other dog populations.

Oskarsson, M. C., Klütsch, C. F., Boonyaprakob, U., Wilton, A., Tanabe, Y., & Savolainen, P. (2012). Mitochondrial DNA data indicate an introduction through Mainland Southeast Asia for Australian dingoes and Polynesian domestic dogs.Proceedings of the Royal Society B: Biological Sciences, 279(1730), 967-974.

In the late stages of the global dispersal of dogs, dingoes appear in the Australian archaeological record 3500 years BP, and dogs were one of three domesticates brought with the colonization of Polynesia, but the introduction routes to this region remain unknown.

This also relates to questions about human history, such as to what extent the Polynesian culture was introduced with the Austronesian expansion from Taiwan or adopted en route, and whether pre-Neolithic Australia was culturally influenced by the surrounding Neolithic world. We investigate these questions by mapping the distribution of the mtDNA founder haplotypes for dingoes (A29) and ancient Polynesian dogs (Arc1 and Arc2) in samples across Southern East Asia (n = 424) and Island Southeast Asia (n = 219). All three haplotypes were found in South China, Mainland Southeast Asia and Indonesia but absent in Taiwan and the Philippines, and the mtDNA diversity among dingoes indicates an introduction to Australia 4600–18 300 years BP. These results suggest that Australian dingoes and Polynesian dogs originate from dogs introduced to Indonesia via Mainland Southeast Asia before the Neolithic, and not from Taiwan together with the Austronesian expansion. This underscores the complex origins of Polynesian culture and the isolation from Neolithic influence of the pre-Neolithic Australian culture.

Feral dogs in Galápagos

Barnett, B. D., & Rudd, R. L. (1983). Feral dogs of the Galápagos Islands: Impact and control. International Journal for the study of Animal Problems, 4:44-58.

Organisms introduced onto insular ecosystems, after they have become established, frequently increase to destructive numbers. Several species of mammals introduced onto the Galápagos Islands illustrate this ecological axiom. For example, domestic or pariah, and feral. Problems derived from their presence are most apparent on the islands of Santa Cruz and Isabela. Feral and pariah dogs are both scavengers and predators. While other introduced mammals (chiefly feral cattle and pigs) have served as prey, in recent years severe depredations on the unique endemic Galapagan fauna have been caused by the dogs. The chief targets have included land and marine iguanas, tortoises, and colonially nesting marine birds. To counter this problem, a coordinated and an eradication program on Isla Isabela, begun in 1981, continues with marked success. Control rests primarily on carefully placed flesh baits poisoned with Compound 1080 (sodium monofluoroacetate). Field studies on distribution, demography, behavior, and disease transmission also began on Isla Isabela in 1981. Particularly notable is the high incidence of filarial heartworm in several species of mammals, including the local human residents. Dogs are important reservoirs of this parasite. Descriptions of the problems created by the dogs and speculations on the nature of selective return to the wild state are presented.

Photo Galapagos Conservation Society

Eradication and control of feral dogs in Galápagos

Barnett, B. D. (1986). Eradication and control of feral and free-ranging dogs in the Galápagos Islands. In Proceedings of the Twelfth Vertebrate Pest Conference (1986) (8 pp.).

The history of canid introduction in Galápagos, their impact on biodiversity and the control and eradication by different methods, mainly poisoning with 1080 and chemical sterilisation.

After eradication in some areas, some mesopredator release effect was detected and cats further threatened iguanas populations. Sea lions became free of this danger, but cattle invaded areas previously occupied by dogs.

The iguana tragedy

Kutschera, U., & Kleinhans, S. 2013. Alfred Russel Wallace and the destruction of island life: the Iguana tragedy. Theory in Biosciences, 1-7.

The Galápagos Islands (Ecuador) are usually associated with the explorations and theoretical deductions of Charles Robert Darwin (1809–1882), but Alfred Russel Wallace (1823–1913) also investigated these islands and published several reports on the living world of this unique archipelago. In contrast to Darwin, Wallace described the destruction of natural ecosystems by humans and foresaw the resulting extinction of species. Here, we outline two case studies pertinent to Wallace’s prediction. First, we summarize the behavior of the predator-naive marine iguanas (Amblyrhynchus cristatus) on the Galápagos Islands, which are threatened by feral dogs and cats imported by humans. We also describe the unique life cycle of the spiny-tailed iguana (Ctenosaura bakeri) from the island of Utila (Honduras), a rare species whose populations are declining because of habitat destructions. In contrast to these threatened, endemic island species, the Green iguana (Iguana iguana) is still widely distributed, although, as a result of de-forestation, in some areas of South America local populations have disappeared. We conclude that Wallace was correct in his prediction that, because of human activities, numerous species of animals and plants will be driven to extinction, notably on islands.

Feral Dog with iguana Photo Galapagos Conservation Society

Farewell to the airport cats: Eradication of feral cats from Baltra island

A three-year program to eradicate feral cats, Felis catus,, from the island of Baltra in the Galápagos archipelago has achieved good results. With the objective of reducing the negative impact produced by the cats and restore a Galápagos ecosystem, the Galápagos National Park (GNP), with technical support from the Charles Darwin Foundation (CDF), began a project with the principal objectives of eradicating cats from Baltra island, and the restoration of its natural habitat. In addition, the project guarantees the survival of a population of repatriated land iguanas Conolophus subcristatus, a species made extinct on this island in the past, partly due to the presence of feral cats.

Eradication of cats was possible for various reasons: firstly, it is an island with a very small human population and therefore with a low risk or re-introduction of cats; its size is small (26km2) which helps control and monitoring; and lastly, the vegetation is sparse, with many open areas. Studies on feral cat behaviour and the most appropriate methods of control revealed that cats are active during the day and night. During the day, GNP staff looked for tracks and signs, and placed traps (Tomahawk and Victor types) and poison. At night, hunters removed cats with spotlights and rifles. With the objective of ensuring total eradication, in 2001, sodium monofluoroacetate (1080) in fish baits was placed over the entire island. The island was divided into 13 sectors and 350 bait stations were placed. This methodology was successful in controlling the cats. The population has slowly been reduced to the point of eradication. Removal of the remaining cats was complicated by a weather-induced eruption of rats Rattus rattus, and mice Mus musculus, that enabled recruitment of kittens in 2002, but made cats more sucseptible to trapping and shooting in 2003 when the rodent population collapsed. By the end of 2003 no sign of a cat was seen on Baltra despite extensive searching. Periodic monitoring on Baltra continues throughout 2004 to confirm the eradication of the feral cats, and the establishment of colonies of repatriated land iguanas. On reduction of the cat population there have been immediate increases in the numbers of locally bred terrestrial iguanas seen during annual censuses. However, this response may reflect the coincidental maturation of young produced by iguanas repatriated from 1991 onwards or climatic variations rather than resulting from reduced cat predation alone. It may be necessary to wait some years to see the full benefits of reduced cat predation. Currently the GNP is carrying out cat control programmes at two sites, Cerro Dragon and Cerro Montura, on another island in Galápagos, Santa Cruz. In addition, they are monitoring other islands to determine the areas where feral cats are threatening native species. 

Source: Galápagos National Park and the Charles Darwin Foundation.

Mammal extinctions and mesopredator release

Hanna, E. & M. Cardillo (2013). Island mammal extinctions are determined by interactive effects of life history, island biogeography and mesopredator suppression. Global Ecology and Biogeography, in press. doi: 10.1111/geb.12103

Abstract:
Aim Understanding extinction on islands is critical for biodiversity conservation. Introduced predators are a major cause of island extinctions, but there have been few large-scale studies of the complexity of the effects of predators on island faunas, or how predation interacts with other factors. Using a large database of island mammal populations, we describe and explain patterns of island mammal extinctions as a function of introduced predators, life history and geography.

Location:

Three hundred and twenty-three Australian islands.

Methods 

We built a database of 934 island mammal populations, extinct and extant, including life history and ecology, island geography and the presence of introduced predators. To test predictors of extinction probability, we used generalized linear mixed models to control partially for phylogenetic non-independence, and decision trees to more fully explore interactive effects.

Results

The decision trees identified large mammals (> 2.7 kg) as having higher extinction probabilities than small species (< 2.7 kg). In large species, extinction patterns are consistent with island biogeography theory, with distance from the mainland being the primary predictor of extinction. For small species, the presence of introduced black rats is the primary predictor of extinction. As predicted by mesopredator suppression theory, extinction probabilities are lower on islands with both black rats and a larger introduced predator (cats, foxes or dingoes), compared with islands with rats but no larger predator. Similarly, extinction probabilities are lower on islands with both a mid-sized (cats or foxes) and a larger (dingoes) predator, compared with islands with cats or foxes only.

Main conclusions 

Island mammal extinctions result from complex interactions of introduced predators, island geography and prey biology. One conservation implication of our results is that eradication of introduced apex predators (cats, foxes or dingoes) from islands could precipitate the expansion of black rat populations, potentially leading to extinction of native mammal species whose remaining populations are confined to islands.