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Denver, CO, United States

Leo V.,University of New South Wales | Reading R.P.,Denver Zoological Foundation | Letnic M.,University of New South Wales
Oecologia | Year: 2015

Apex predators can impact smaller predators via lethal effects that occur through direct killing, and non-lethal effects that arise when fear-induced behavioural and physiological changes reduce the fitness of smaller predators. A general outcome of asymmetrical competition between co-existing predator species is that larger predators tend to suppress the abundances of smaller predators. Here, we investigate interference effectsthat an apex predator, the dingo (Canis dingo), has on the acquisition of food and water by the smaller red fox (Vulpes vulpes), by exposing free-ranging foxes to the odour of dingoes and conspecifics in an arid environment. Using giving-up densities we show that foxes foraged more apprehensively at predator-odour treatments than unscented controls, but their food intake did not differ between dingo- and fox-odour treatments. Using video analysis of fox behaviour at experimental water stations we show that foxes spent more time engaged in exploration behaviour at stations scented with fox odour and spent more time drinking at water stations scented with dingo odour. Our results provide support for the idea that dingo odour exerts a stronger interference effect on foxes than conspecific odour, but suggest that the odours of both larger dingoes and unfamiliar conspecifics curtailed foxes’ acquisition of food resources. © 2015 Springer-Verlag Berlin Heidelberg

Parker G.,Marwell Wildlife | Sundaresan S.,Denver Zoological Foundation | Sundaresan S.,Princeton University | Chege G.,Lewa Wildlife Conservancy | And 2 more authors.
African Journal of Ecology | Year: 2011

The effective management of endangered mammals requires reliable estimates of population size. This is challenging for species such as Grevy's zebra (Equus grevyi) that are distributed over large areas at low densities. Less than 2500 Grevy's zebra remain in the wild, scattered across 85,000km2 of savannah in northern Kenya and Ethiopia. An efficient, accurate and repeatable survey method is required to guide conservation planning for the species. Currently, total aerial counts are used to census endangered species within Kenya, but are costly in terms of resources. In this study, we evaluated the suitability of sample survey methods for Grevy's zebra. We estimated population size using sample aerial counts for a known population of Grevy's zebra in Lewa Wildlife Conservancy (LWC), providing the opportunity to test the accuracy of sample methods, while comparing resource costs with total count methods. We sampled one-third of LWC using parallel 500-m strip transects at 1500-m intervals. The population estimate was comparable to the known population size and was less than half as expensive as the equivalent total count survey. Our results suggest sample aerial surveys provide an accurate and cost-effective means of monitoring Grevy's zebra and other endangered species in open habitats. +Résumé: La gestion efficace de mammifères en danger exige des estimations fiables de la taille des populations. Ceci est un vrai défi pour des espèces telles que le zèbre de Grévy (Equus grevyi) qui sont distribuées en faible densité sur de vastes étendues. Il reste moins de 2500 zèbres de Grévy dans la nature, éparpillés sur quelque 85.000km2 de savane, dans le nord du Kenya et en Ethiopie. Il faut une méthode d'étude efficace, exacte et reproductible pour guider la planification de la conservation de cette espèce. Actuellement, on a recours à des comptages aériens totaux pour recenser les espèces menacées au Kenya, mais c'est une méthode coûteuse. Dans cette étude, nous avons évalué l'opportunité de méthodes par échantillons pour le zèbre de Grévy. Nous avons estimé la taille de la population en utilisant des comptages échantillons d'une population de zèbres de Grévy connue dans la Lewa Wildlife Conservancy (LWC), ce qui nous a donné l'occasion de tester l'exactitude de méthodes par échantillons tout en comparant les coûts avec les méthodes de comptage complet. Nous avons échantillonné un tiers de LWC en traçant des transects parallèles de 500m de large à intervalles de 1500m. L'estimation de la population était comparable à sa taille connue, et elle a coûté moins de la moitié du dénombrement total équivalent. Nos résultats suggèrent que des recherches aériennes par échantillons sont un moyen précis et économique de suivre le zèbre de Grévy et d'autres espèces en danger dans des habitats ouverts. © 2010 Blackwell Publishing Ltd.

Reading R.P.,Denver Zoological Foundation | Miller B.,Wind River
Zoo Biology | Year: 2013

Reintroduction attempts have faced low, albeit improving, success rates, especially for threatened and endangered species reintroduced from captivity to the wild. This is not only a concern for conservation, as the low success of reintroduction also implies an animal welfare issue for the individuals concerned. Success rates are particularly low for species that live in complex social structures, require greater training during development, and exhibit higher levels of intelligence. Aside from mitigating the original cause of a species extirpation from an area, behavior factors arguably represent the most important aspect influencing an animal's survival following reintroduction. Indeed, we previously recommended using behavioral indicators for determining relative reintroduction success, especially as practitioners develop and compare protocols or if survivorship is difficult to gauge. Strategic enrichment programs targeted toward developing specific skills important for survival in the wild promise to improve reintroduction success by providing individuals with opportunities to develop and improve behavioral skills, such as avoiding predation, foraging (especially for predators and primates), interacting in social groups, courtship and mating, habitat selection, and learning movement and migration routes. Enrichment also improves the physical condition of most individuals, which should also increase reintroduction success. Last but not least, such programs offer the prospect of improved animal welfare both pre- and post-release. We explore how behavioral enrichment has influenced reintroduction success and welfare in a variety of different species. © 2013 Wiley Periodicals Inc.

Magle S.B.,Urban Wildlife Institute | Salamack K.A.,Wildlife Habitat Council | Crooks K.R.,Colorado State University | Reading R.P.,Denver Zoological Foundation
Biodiversity and Conservation | Year: 2012

Urbanization and habitat fragmentation have the potential to influence bird communities. In addition, these phenomena, as well as ongoing lethal control measures, have also greatly reduced the range of the black-tailed prairie dog (Cynomys ludovicianus) since the beginning of the 20th century. Although prairie dogs are highly interactive species that can influence avian communities, few studies have investigated whether these interactions persist in urban settings. Our goal was to investigate the relative impacts of habitat fragmentation and prairie dogs on bird communities within an urban matrix. We performed bird surveys on 20 habitat fragments (10 colonized by prairie dogs, 10 uncolonized by prairie dogs) distributed throughout the Denver metropolitan area, and calculated Shannon-Weiner diversity and richness of all birds and native species, as well as total counts of grassland birds and raptors. Diversity, richness, and counts of many species increased with increasing fragment connectivity, and decreased on fragments isolated for longer periods of time. Avian diversity and richness did not differ between fragments with and without prairie dogs, suggesting that this element of the ecological role of prairie dogs is not fully retained in urban habitat. Future studies of the role of prairie dogs as keystone species in urban systems should include other taxa as well as consider the influence of the urban matrix surrounding prairie dog habitat. Our results emphasize that conservation of urban avian diversity should focus on landscape connectivity as well as local habitat features. © 2012 Springer Science+Business Media B.V.

Miller B.,Wind River | Reading R.P.,Denver Zoological Foundation
Western North American Naturalist | Year: 2012

The black-footed ferret (Mustela nigripes) recovery program is an example of single-species management to preserve flora and fauna. We argue that conservationists must move beyond that approach for success. In 1988, the U.S. Fish and Wildlife Service proposed a down-listing goal of 1500 adult black-footed ferrets in 10 wild populations by 2010. The recovery program has only reached 23% of that goal. The overriding reason is the lack of regulatory mechanisms for poisoning and shooting prairie dogs (Cynomys spp.) and our inability to control occurrence of plague (Yersinia pestis) in prairie dogs. We propose that prairie dogs need, and deserve, some level of federal protection to address these factors and that the primary goal for conservation of black-footed ferrets should be maintaining numbers and distributions of prairie dogs at sufficient temporal and geographic scales to restore them to a level of ecological function in the grasslands. We contend that prairie dogs qualify for protection in at least 4 of the 5 categories used to assess level of threat under the Endangered Species Act. A species needs to qualify in one of those categories to merit protection. The threat posed by plague should itself be sufficient reason to justify prairie dog protection, both for themselves and for the black-footed ferret recovery program.

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