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The current literature on resource selection by animals is a maze of methodologies for data collection and interpretation. Field biologists need a guide through the labyrinth. This book provides such a guide. It gives a clear and consistent framework for the study of how animals select their resources (food and habitat) by taking the reader through different types of study design. It is an invaluable handbook for the field biologist, especially those concerned with the management and conservation of wildlife. The authors have clearly identified the need to pull together the diffuse literature, and biologists will greatly improve their experimental design, methodology, and analysis with this book. The second edition of this popular book has been updated to include many developments in the last few years. There is new material on discrete choice models, the analysis of data from geographical information systems, compositional analysis, Mahalanobis distance methods, and neural networks and related approaches. Resource Selection by Animals:
We have written this book as a guide to the design and analysis of field studies of resource selection, concentrating primarily on statistical aspects of the comparison of the use and availability of resources of different types. Our intended audience is field ecologists in general and, in particular, wildlife and fisheries biologists who are attempting to measure the extent to which real animal populations are selective in their choice of food and habitat. As such, we have made no attempt to address those aspects of theoretical ecology that are concerned with how animals might choose their resources if they acted in an optimal manner. The book is based on the concept of a resource selection function (RSF), where this is a function of characteristics measured on resourceunits such that its value for a unit is proportional to the probability of that unit being used. We argue that this concept leads to a unified theory for the analysis and interpretation of data on resource selection and can replace many ad hoc statistical methods that have been used in the past.
Every day, biologists in parkas, raincoats, and rubber boots go into the field to capture and mark a variety of animal species. Back in the office, statisticians create analytical models for the field biologists' data. But many times, representatives of the two professions do not fully understand one another's roles. This book bridges this gap by helping biologists understand state-of-the-art statistical methods for analyzing capture-recapture data. In so doing, statisticians will also become more familiar with the design of field studies and with the real-life issues facing biologists. Reliable outcomes of capture-recapture studies are vital to answering key ecological questions. Is the population increasing or decreasing? Do more or fewer animals have a particular characteristic? In answering these questions, biologists cannot hope to capture and mark entire populations. And frequently, the populations change unpredictably during a study. Thus, increasingly sophisticated models have been employed to convert data into answers to ecological questions. This book, by experts in capture-recapture analysis, introduces the most up-to-date methods for data analysis while explaining the theory behind those methods. Thorough, concise, and portable, it will be immensely useful to biologists, biometricians, and statisticians, students in both fields, and anyone else engaged in the capture-recapture process.
Public concerns over large losses of wild ungulates to predators arise when restoring large carnivore species to former locations or population densities. During the 1990s, mountain lion (Felis concolor) and grizzly bear (Ursus arctos) numbers increased in Jackson Hole, Wyoming, and gray wolves (Canis lupus) were reintroduced to the Greater Yellowstone Ecosystem. We investigated effects of these predators, as well as black bears (Ursus americanus) and coyotes (Canis latrans), on mortality of an abundant and increasing prey species, elk (Cervus elaphus). We captured, radio-instrumented, and monitored survival of 145 elk neonates from 3 cohorts during 1990 - 1992, and 153 neonates from 3 cohorts during 1997 - 1999 when grizzly bears and lions were likely more common than during the earlier period of study. Neonatal (birth through 31 July) mortality of elk due to predation, disease, and accidents increased from 15.2 % to 27.5% (P = 0.01). Sixty-eight percent of all mortality during 1990 - 1992 resulted from predation by black bears and coyotes, compared to 76% during 1997-1999 by black bears, coyotes, grizzly bears, and mountain lions, a non-significant difference (P = 0.49). Weight gains of calves during the first week, but not birth weights, declined from 1990 - 1992 to 1997 - 1999. April temperatures were cooler, delaying spring green-up, and elk numbers were larger during 1997 - 1999 when weight gains and survival of calves declined. Calves that died were more likely to be male, below average birth weight, and had inferior serum nutritional indices. The change in neonatal calf survival reduced the annual growth rate of the Jackson elk herd from 1.26 to 1.23, yielding a decline in the annual increment of approximately 500 animals in a preparturition herd of 11,000 elk. Changes in mid-summer calf: 100 cow ratios indicated a 39 - 45% greater decline in neonatal survival than measured among the radioed calves. We suggest increasing predation during the study was partially compensatory, given predator selection of inferior calves and increased mortality of cohorts with reduced first week growth rates. Reduced rate of first week weight gains of elk calves extended the duration of neonatal mortality by one month during 1997 - 1999, and may be as important in predisposing calves to predation and other mortality as low birth weights. Consequently, we conclude that increased predation was a proximate not an ultimate cause of declining neonatal survival during the 1990s. We recommend careful evaluation and hypothesis testing of predator effects on elk as restoration of large carnivores continues.
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