Roger A Powell

• Professor Emeritus at North Carolina State University

The stone marten (Martes foina) is an important species for cytogenetic studies in the order Carnivora. ZooFISH probes created from its chromosomes provided a strong and clean signal in chromosome painting experiments and were valuable for studying the evolution of carnivoran genome architecture. The research revealed that the stone marten chromoso...

The social system of animals involves a complex interplay between physiology, natural history, and the environment. Long relied upon discrete categorizations of “social” and “solitary” inhibit our capacity to understand species and their interactions with the world around them. Here, we use a globally distributed camera trapping dataset to test the...

The presence and abundance of organisms within an ecosystem often correlate with habitat variables that may have few, or unknown, functional values. Understanding the functional role of these variables is especially important for organisms occupying landscapes managed for timber production and containing diverse habitat patches of different quantit...

Humans interact with wildlife regularly, mostly without conflict. Interactions between humans and bears, however, have a history of conflict. Using data from female black bears in two populations, we compared behaviors related to a series of hypotheses about habituation and food supplementation via research feeding. We livetrapped bears in the sout...

Understanding the role of landscapes managed for timber production in the conservation of forest-obligate species is a priority for preserving ecological integrity and fostering socioeconomic wellbeing. The forest characteristics generally associated with the survival, reproduction, and persistence of forest-obligate species (e.g., large-diameter t...

Abstract Effects of historical fire suppression in forested ecosystems, combined with increasingly frequent and prolonged periods of drought due to a changing climate, are predicted to drive increases in the extent and intensity of wildfires in western North America and elsewhere. Understanding the effects of wildfires on forest‐dependent species a...

Sleep is important for memory consolidation and maintaining metabolic homeostasis, but sleep can expose animals to inclement weather and predators. Consequently, selection of sleeping sites is important. We tested three sets of hypotheses related to selection of bed sites by female American black bears (Ursus americanus) at two study sites. During...

Animals exploring a new environment develop cognitive maps using diverse sensory input and, thereby, gain information needed to establish home ranges. Experiencing, and learning information about, resources should be advantageous to the resident of a home range while lack of such information should put invaders into the home range at a disadvantage...

Human-dominated landscapes contain fragmented natural land cover interspersed throughout an urban matrix. Animals that occupy human-dominated landscapes often grow and reproduce differently than conspecifics. Female American black bears (Ursus americanus) produce litters for the first time usually at age 4 years; 2-year-olds rarely give birth. We v...

Breeding systems affect the timing of reproduction, spacing patterns and social organization, individual fitnesses, and population sizes. For many species, information on breeding systems and mating is limited or untested in wild populations, resulting in management actions that are incompletely informed. We used photographic data collected on a re...

The literature on fishers - medium-sized, North American carnivores - is broad, despite being limited, and traditional ecological knowledge of Native Americans contributes to our understanding of fishers. Fishers are generalist predators but also specialized predators of North American porcupines. Over trapping, habitat loss and climate change redu...

Determining how species coexist is critical for understanding functional diversity, niche partitioning and interspecific interactions. Identifying the direct and indirect interactions among sympatric carnivores that enable their coexistence is particularly important to elucidate because they are integral for maintaining ecosystem function. We studi...

This letter was submitted by several scientists across North America in reply to a response from Alberta's S. Boutin regarding killing wolves under the guise of caribou recovery.

In his News In Depth story “To save caribou, Alberta wants to fence them in” (22 July, p. [333][1]), W. Cornwall reported on a proposed 50-year-long project to create a predator-free, fenced, 100-square-kilometer landscape to farm caribou in the Little Smoky range. The program intends to kill

Monitoring mammals is becoming increasingly important as state and federal agencies develop wildlife action plans addressing increased urbanization and climatechange impacts on plant and animal populations. We designed and implemented surveys applicable to forested wetlands to assess detection rates, estimate species richness, compare species distr...

Timing can be critical for many life history events of organisms. Consequently, the timing of management activities may affect individuals and populations in numerous and unforeseen ways. Translocations of organisms are used to restore or expand populations but the timing of translocations is largely unexplored as a factor influencing population su...

Although killing neck snares are used on traplines in Canada to capture gray wolves (Canis lupus), coyotes (C. latrans), and red foxes (Vulpes vulpes), they are not subject to trap performance criteria set out in the Agreement on International Humane Trapping Standards (AIHTS). This paper reviews scientific information related to the humaneness and...

The recent co-occurrence of red wolves (Canis rufus) and coyotes (Canis latrans) in eastern North Carolina provides a unique opportunity to study prey partitioning by sympatric canids. We collected scats from this region and examined them for prey contents. We used fecal DNA analysis to identify which taxa deposited each scat and multinomial modeli...

The objective of this study was to determine if housing conditions, specifically pen size and soil enrichment, had an effect on faecal glucocorticoid concentrations in the endangered pygmy rabbit. The success of the captive breeding program has been limited, so one hypothesis is that chronic stress due to suboptimal housing conditions may be respon...

Understanding behavioral changes of prey and predators based on lunar illumination provides insight into important life history, behavioral ecology, and survival information. The objectives of this research were to determine if bobcat movement rates differed by period of day (dark, moon, crepuscular, day), lunar illumination (<10%, 10 - <50%, 50 -...

Historically, overexploitation, loss and fragmentation of forest habitats, predator control, and climate change caused population decreases and local extirpations of Martes populations. Protection led to population recovery in some places but not everywhere. Because these predators are important components of their natural ecological communities an...

Home ranges relate to all aspects of a mammal's biology. The 5 papers in this Special Feature provide statistical, economic, game theoretic, mechanistic, information dependent, and conceptual approaches to understanding home ranges and why animals have them. All the papers emphasize the importance of testing a priori hypotheses, especially hypothes...

"Home range" is a standard concept in animal ecology and behavior but few people try to understand what home ranges mean to the animals that have them and often assume that a home-range estimate, quantified using some method, is the home range. This leads to 2 problems. First, researchers put much energy into discerning and using the "best" methods...

Home ranges relate to all aspects of a mammal's biology. The 5 papers in this Special Feature provide statistical, economic, game theoretic, mechanistic, information dependent, and conceptual approaches to understanding home ranges and why animals have them. All the papers emphasize the importance of testing a priori hypotheses, especially hypothes...

Economic models predict behavior of animals based on the presumption that natural selection has shaped behaviors important to an animal's fitness to maximize benefits over costs. Economic analyses have shown that territories of animals are structured by trade-offs between benefits gained from resources and costs of defending them. Intuitively, home...

The Columbia Basin pygmy rabbit (Brachylagus idahoensis) is critically endangered and the focus of a captive-breeding program. However, reproductive success in captivity to date has not been sufficient to sustain reintroduction efforts. The goal of this study was to investigate patterns of fecal progestagen and glucocorticoid excretion in females d...

Translocations are frequently used to restore extirpated carnivore populations. Understanding the factors that influence translocation success is important because carnivore translocations can be time consuming, expensive, and controversial. Using population viability software, we modeled reintroductions of the fisher, a candidate for endangered or...

A program file created for our VORTEX simulations is included as supplemental information to interested readers (Program File S1.vpj). (VPJ)

The complete set of attribute data used in our analyses of 38 fisher translocations, listed chronologically. References in this table refer to sources listed in the reference section of the manuscript. (DOC)

The stoat (Mustela erminea) is a specialist predator that evolved to exploit the unstable populations of northern voles and lemmings. It was introduced to New Zealand, where it is pre-adapted to respond with a population irruption to the resource pulses that follow a heavy seedfall of southern beech (Nothofagus spp.). Culling stoats during an irrup...

Anesthetic protocols that allow quick induction, short processing time, and rapid reversal are necessary for researchers performing minimally invasive procedures (including morphometric measurements or attachment of radiocollars). The objective of this study was to evaluate the effectiveness of medetomidine and butorphanol as a substitute for xylaz...

Ecologically equivalent species serve similar functions in different communities, and an ecological surrogate species can be used as a substitute for an equivalent species in a community. Siberian polecats (Mustela eversmanii) and black-footed ferrets (M. nigripes) have long been considered ecological equivalents. Polecats also have been used as in...

Black-footed ferrets (Mustela nigripes) likely were extirpated from the wild in 1985—1986, and their repatriation depends on captive breeding and reintroduction. Postrelease survival of animals can be affected by behavioral changes induced by captivity. We released neutered Siberian polecats (M. eversmanii), close relatives of ferrets, in 1989—1990...

In 2001, the sudden collapse of the Columbia Basin population of pygmy rabbits prompted the initiation of a captive breeding program to facilitate reintroduction, but reproductive success in captivity has not met expectations. Therefore, the objective of this study was to characterize the reproductive and adrenal endocrinology of this endangered ra...

We assert that researchers should use statistics derived from the linear distances between actual and estimated locations of test transmitters to estimate location error in radiotelemetry data. We call this approach the location error method. We used the distribution of such linear distances from a test data set from a study on black bears (Ursus a...

Capture-recapture, radiotelemetry (on a monthly and a yearly basis), and age-distribution methods were used to estimate annual survival rates for black bears (Ursus americanus) in the southern Appalachians from 1981 to 1996. Using capture-recapture data, the Jolly-Seber estimator calculated the annual survival rate for all bears over all years to b...

Global positioning system (GPS) telemetry technology allows us to monitor and to map the details of animal movement, securing vast quantities of such data even for highly cryptic organisms. We envision an exciting synergy between animal ecology and GPS-based radiotelemetry, as for other examples of new technologies stimulating rapid conceptual adva...

Recent advances in animal tracking and telemetry technology have allowed the collection of location data at an ever-increasing rate and accuracy, and these advances have been accompanied by the development of new methods of data analysis for portraying space use, home ranges and utilization distributions. New statistical approaches include data-int...

The field of habitat ecology has been muddled by imprecise terminology regarding what constitutes habitat, and how importance is measured through use, selection, avoidance and other bio-statistical terminology. Added to the confusion is the idea that habitat is scale-specific. Despite these conceptual difficulties, ecologists have made advances in...

While the mechanistic links between animal movement and population dynamics are ecologically obvious, it is much less clear when knowledge of animal movement is a prerequisite for understanding and predicting population dynamics. GPS and other technologies enable detailed tracking of animal location concurrently with acquisition of landscape data a...

This is a review of mustelid spacing patterns. The Mustelinae appear to have intrasexual territories where ♂♂ are territorial against ♂♂, ♀♀ against ♀♀, but there is extensive territory overlap between sexes. Mustelids of other subfamilies appear to have variations on this theme; usually female territories are replaced by territories of family grou...

Weasels are the most common and the least known of the world's carnivores. In predatory power they rival any of the big cats; indeed, gram for gram they are much stronger than any lion. But they are small and hard to see in the wild, and they can live their secret lives alongside people who never guess that they are there. In their native environme...

Analyses of large, long-lived animals suggest that adult survival generally has the potential to contribute more than reproduction to population growth rate (λ), but because survival varies little, high variability in reproduction can have a greater influence. This pattern has been documented for several species of large mammals, but few studies ha...

We evaluated selection of den sites by American black bears (Ursus americanus) in the Pisgah Bear Sanctuary, western North Carolina, by comparing characteristics of dens at 53 den sites with availability of habitat characteristics in annual home ranges of bears and in the study area. We also tested whether den-site selection differed by sex, age, a...

Home ranges of animals are generally structured by the selective use of resource-bearing patches that comprise habitat. Based on this concept, home ranges of animals estimated from location data are commonly used to infer habitat relationships. Because home ranges estimated from animal locations are largely continuous in space, the resource-bearing...

The need to capture wild animals for conservation, research, and management is well justified, but long-term effects of capture and handling remain unclear. We analyzed standard types of data collected from 127 grizzly bears (Ursus arctos) captured 239 times in western Alberta, Canada, 1999-2005, and 213 American black bears (U. americanus) capture...

1. Understanding contributions of cohort effects to variation in population growth of fluctuating populations is of great interest in evolutionary biology and may be critical in contributing towards wildlife and conservation management. Cohort-specific contributions to population growth can be evaluated using age-specific matrix models and associat...

Research has shown that territories of animals are economical. Home ranges should be similarly efficient with respect to spatially distributed resources and this should structure their distribution on a landscape, although neither has been demonstrated empirically. To test these hypotheses, we used home range models that optimize resource use accor...

Soft mast is an important resource for many wild populations in the Southern Appalachians, yet the way clear-cutting affects availability of soft mast though time is not fully understood. We tested a theoretical model of temporal availability of soft mast in clearcuts using empirical data on percent cover and berry production of Gaylussacia, Vaccin...

Much research on wild mammals requires trapping, especially livetrapping, yet few methods used to capture wild mammals have been tested against an accepted standard for animal welfare and few data exist regarding physiological responses to capture. My coworkers and I livetrapped 208 American black bears (Ursus americanus) 356 times between May 1981...

Martens (members of the genus Martes) maintain home ranges because the long-term benefits (food, access to mates, rest sites, information, etc.) from doing so exceed the long-term costs (travel, risk of predation, competitors, etc.). Martens appear to have cognitive maps of their home ranges, which one might envision as an integration of contour ma...

Home ranges of animals are associated with the spatial distribution of limiting resources on a landscape, yet no mechanistic models representing this relationship exist. We present models of how animals might choose patches for their home ranges in ways that are optimal with respect to spatially distributed resources. The models assume that animals...

Models are described for the joint analysis of live-trapping and radio telemetry data from a study on black bears (Ursus americanus) in which all animals received ear tags and a subset also received radio tags. Concerns about bias in survival estimates led to investigation of identifiability and estimator precision for a series of models that allow...

We evaluated responses of black bears (Ursus americanus) to changes in habitat in the Pisgah National Forest in North Carolina, USA. Changes in habitat were due to forest management, which affected bear habitat in complex ways. Harvested stands provided plentiful food resources that decreased with regeneration of the canopy. However, their value wa...

We used radiotelemetry and microsatellite DNA analysis to investigate the influence of body size on male mating tactics and short-term reproductive success in the black bear. We investigated male ranging behaviour and documented male encounters with breeding females to determine whether males employed conditional mating tactics according to their b...

We propose that researchers integrate ethics, performance criteria, techniques, and common sense when developing research trapping programs and in which members of institutional animal care and use committees address these topics when evaluating research protocols. To ask questions about ethics is in the best tradition of science, and researchers m...

We present a habitat suitability index (HSI) model for black bears (Ursus americanus) living in the southern Appalachians that was developed a priori from the literature, then tested using location and home range data collected in the Pisgah Bear Sanctuary, North Carolina, over a 12-year period. The HSI was developed and initially tested using habi...

A review of the commonly measured habitat factors that affect American martens and fishers is presented. Preferences for cover types and for specific habitat features by the North American Martes are compared, and biological principles are identified that may explain habitat selection by these species.

The topography of an area affects the animals that live in at. Using digitized topographic maps of our mountainous study area in North Carolina. USA, and using radio telemetry data for locations of black bears Ursus americanus, we tested the hypotheses that topography influences home ranges of black bears and that topography affects access to resou...

Capture-recapture, radiotelemetry ton a monthly and a yearly basis), and age-distribution methods were used to estimate annual survival rates for black bears (Ursus americanus) in the southern Appalachians from 1981 to 1996. Using capture-recapture data, the Jolly-Seber estimator calculated the annual survival rate for all bears over all years to b...

Kernel methods are state of the art for estimating animal home-range area and utilization distribution (UD). The KERNELHR program was developed to provide researchers and managers a tool to implement this extremely flexible set of methods with many variants. KERNELHR runs interactively or from the command line on any personal computer (PC) running...

Most hypotheses attempting to explain the evolution of pronounced sexual dimorphism in body size in the three species of weasels (Mustela erminea, M. frenata, M. nivalis) assume that sexual dimorphism is a long-term adaptation, associated with the different reproductive strategies of the two sexes. We here examine an auxiliary hypothesis which pred...

Most hypotheses attempting to explain the evolution of pronounced sexual dimorphism in body size in the three species of weasels (Mustela erminea,M. frenata,M. nivalis) assume that sexual dimorphism is a long-term adaptation, associated with the different reproductive strategies of the two sexes. We here examine an auxiliary hypothesis which predic...

Kernel density estimators are becoming more widely used, particularly as home range estimators. Despite extensive interest in their theoretical properties, little empirical research has been done to investigate their performance as home range estimators. We used computer simulations to compare the area and shape of kernel density estimates to the t...

Studying one of two bear species not experiencing widespread population decline, provides insight into the population responses of the six bear species that are in decline and into responses of other long-lived species for which data are difficult to collect. Black bear (Ursus americanus) sanctuaries were established in North Carolina (U.S.) in 197...

Several researchers reported that fishers (Martes pennanti) select lowland-conifer habitats, where snowshoe hares (Lepus americanus) are abundant, for foraging and resting and therefore, avoid open, upland-hardwood habitats. In the Ottawa National Forest, Upper Peninsula, Michigan, in the 1970s, porcupines (Erethizon dorsatum) occurred in open, upl...

We quantified the behavior of juvenile pine voles (Microtus pinetorum) in families maintained in outdoor enclosures protected from rain and predators and determined the effects of number of juveniles present (0-3) on their younger siblings and their parents. juveniles exhibited behaviors characteristic of helpers in cooperative breeding species: br...