Paul D. Curtis

Estimating black bear density using DNA data from hair snares.

Abstract DNA-based mark–recapture has become a methodological cornerstone of research focused on bear species. The objective of such studies is often to estimate population size; however, doing so is frequently complicated by movement of individual bears. Movement affects the probability of detection and the assumption of closure of the population required in most models. To mitigate the bias caused by movement of individuals, population size and density estimates are often adjusted using ad hoc methods, including buffering the minimum polygon of the trapping array. We used a hierarchical, spatial capture–recapture model that contains explicit components for the spatial-point process that governs the distribution of individuals and their exposure to (via movement), and detection by, traps. We modeled detection probability as a function of each individuals distance to the trap and an indicator variable for previous capture to account for possible behavioral responses. We applied our model to a 2006 hair-snare study of a black bear (Ursus americanus) population in northern New York, USA. Based on the microsatellite marker analysis of collected hair samples, 47 individuals were identified. We estimated mean density at 0.20 bears/km2. A positive estimate of the indicator variable suggests that bears are attracted to baited sites; therefore, including a trap-dependence covariate is important when using bait to attract individuals. Bayesian analysis of the model was implemented in WinBUGS, and we provide the model specification. The model can be applied to any spatially organized trapping array (hair snares, camera traps, mist nests, etc.) to estimate density and can also account for heterogeneity and covariate information at the trap or individual level.

Methods to Reduce Traffic Crashes Involving Deer: What Works and What Does Not

More than 1.5 million traffic crashes involving deer, producing at least

Education programs for reducing American black bear–human conflict: indicators of success?

1.1 billion in vehicle damage and about 150 fatalities, are estimated to occur annually in the United States. Deer-related crashes are increasing as both deer populations and vehicular travel increase. Many methods have been used in attempts to reduce deer crashes, often with little scientific foundation and limited evaluation. This article summarizes the methods and reviews the evidence of their effectiveness and the situations in which each may be useful. The only widely accepted method with solid evidence of effectiveness is well-designed and maintained fencing, combined with underpasses or overpasses as appropriate. Herd reduction is controversial but can be effective. Deer whistles appear useless. Roadside reflectors appear to have little long-term effect, although additional well-designed evaluations are needed before firm conclusions can be drawn. Both temporary passive signs and active signs appear promising in specific situations, but considerable research is required to evaluate long-term driver response and to improve and test deer detection technology for active signs. Other methods using advanced technology require substantial additional research and evaluation.

Farmer Perceptions of Crop Damage by Wildlife in Jigme Singye Wangchuck National Park, Bhutan

Abstract Education programs designed to reduce conflicts between American black bears (Ursus americanus) and humans are often implemented by diverse groups of wildlife practitioners who may devote significant resources to these programs, yet little has been done to characterize the content, structure, and effectiveness of these programs. We review 6 education programs in North America. We build on a common performance indicator used in 5 of 6 programs—a reduction in the number of bear–related complaints to wildlife authorities—and suggest that practitioners incorporate other explanatory variables such as human dimensions, weather, natural food, or number of bears harvested. Some of these explanatory variables draw on potentially existing databases; others require new databases. If education programs are to remain an integral part of bear conservation and management, evaluation is essential to understand the ability of such programs to reduce conflict and encourage coexistence between people and bears.

Time to reduction: Factors influencing management efficacy in sterilizing overabundant white-tailed deer

Abstract In the protected areas of Bhutan, crop damage by wildlife impacts the livelihoods of local agropastoralists. We interviewed a stratified-random sample of 274 farmers living in the Jigme Singye Wangchuck National Park in an attempt to better understand and manage growing concerns. Most of the farmers interviewed suffered major financial losses annually due to crop damage by wild pigs (Sus scrofa), barking deer (Muntiacus muntjak), macaques (Macaca mulatta), and sambars (Cervus unicolor). All respondents reported crop losses to wild animals, and wild pig was the most common cause (97%). Farmers responded by implementing nonlethal methods such as guarding, fencing, and performing religious rituals to protect their crops. Growers blamed the parks conservation policies for the high level of reported losses. Crop damage, especially by macaques, increased after establishment of the park in 1993 and implementation of the Forest and Nature Conservation Act of 1995. Management actions should focus on increasing tolerance among farmers and reducing severe losses caused by wild pigs and macaques.

Managing an Overabundant Deer Population by Sterilization: Effects of Immigration, Stochasticity and the Capture Process

In managing overabundant white-tailed deer (Odocoileus virginianus), fertility control frequently is regarded as a viable alternative to lethal strategies. However, little information is available concerning expected duration of fertility control. Our objectives were to create a flexible model for application in a diverse array of environmental conditions, determine the extent to which various parameters contributed to population growth, and assess the time necessary to reduce a population to a given level. The modeled population was assumed geographically closed without density dependence. Using prospective perturbation analysis on a linear time-invariant Lefkovitch matrix model, survival rates contributed to overall population growth nearly twice that of birth rates. Using numerical analysis, a general relationship between annual sterilization rate, desired population reduction, and time to that reduction was determined. This relationship was nonlinear and showed decreased efficiency per unit effort. Depending on local parameter values, we determined that a population could be reduced by 30% to 60% in 4-10 years if a manager could sterilize 25-50% of available fertile females annually. Thus, sterilization may be a viable option for communities with the financial resources and political will to sterilize.

The Role of Ethical Judgments Related to Wildlife Fertility Control

Abstract Fertility control is an alternative to lethal removal for managing overabundant populations. This approach invokes several simplifying assumptions; in particular, that specific individuals can be targeted for sterilization. We evaluated the influence of relaxing this assumption on the likelihood of achieving population control by considering potential sources of variation in the capture and sterilization process in an overabundant white-tailed deer (Odocoileus virginianus) population in Cayuga Heights, New York, USA. Using numerical analysis of an individually based seasonal projection model, including demographic stochasticity, we found that heterogeneity in both sampling, and response to trapping, increased the effort required to achieve population reduction within some acceptable degree of certainty. The inability to precisely control the demographic structure of captured deer required increased capture effort to achieve a given reduction. Trap-aversive behavior following capture improved the efficacy of sterilization while trap affinity reduced it. The efficacy of sterilization as a management tool was reduced dramatically by the presence of net immigration and emigration from the population. We found that sterilization could reduce growth rates of overabundant populations under some conditions, but it is unlikely to be a viable means for reducing populations in general, where there is significant net movement of individuals into the population, and where there is imprecise control over the capture process.

HABITAT FEATURES AFFECTING BEAVER OCCUPANCY ALONG ROADSIDES IN NEW YORK STATE

Certain species of wildlife cause considerable damage and therefore receive management attention. Traditional management methods rely on lethal control, but fertility control is increasingly being advocated as a more humane alternative. Because wildlife management decisions are influenced by citizen input, it is important to understand what makes people support or oppose lethal control and fertility control. We studied six U.S. communities trying to manage large populations of white-tailed deer or feral cats and categorized the ethical arguments citizens used to support their positions on lethal and fertility control methods. We identified two broad categories of ethical arguments. Arguments in the “obligations to people” category focused on (1) decision-making procedures, (2) public policy decisions, and (3) management outcomes. Arguments in the “obligations to animals and the environment” category focused on (1) life, suffering, and death, (2) altered characteristics of animals, (3) individuals and communities, and (4) invasive species impacts.

Developing a plant-based vole repellent: screening of ten candidate species

Abstract Characterizing habitat features that influence beaver (Castor canadensis) occupancy along roadsides may have important implications for managing damage to roads caused by beaver activity. We initiated this study to develop proactive and long-term approaches to deal with nuisance beaver along roadsides. From June to October 1997 and 1998, we sampled 316 roadside sites in New York state, USA—216 sites where beaver occupied the roadside area and 100 unoccupied sites. We used stepwise logistic regression to identify habitat variables associated with beaver occupancy along roadsides. We evaluated regression models through measures of sensitivity and specificity. The logistic function retained the percentage of roadside area devoid of woody vegetation, stream gradient, the interaction between these 2 variables, and stream width in the final model. Precluding beaver occupancy along highways would necessarily involve large-scale removal of woody vegetation that would be impractical in all but the most intensive management scenarios. However, beaver habitat assessment adjacent to roads may be a useful tool for designing new highways, prioritizing culvert replacements, and developing proactive plans for beaver damage management.

Biochemical Variables in Free-ranging White-tailed Deer (Odocoileus virginianus) after Chemical Immobilization in Clover Traps or Via Ground-darting

Voles are a major pest in orchards and coniferous plantations. Currently, vole control relies primarily on the use of rodenticides and herbicides. Our goal was to identify a plant species that could be used to develop a non-lethal and effective repellent. No-choice feeding trials with prairie voles (Microtus ochrogaster, Wagner) were used to assess the relative ability of 10 plant species to deter voles from consuming a preferred food, applesauce. Two highly preferred forage plants were included in the trials for comparative purposes. Finely ground leaves of each of the 12 species were mixed with applesauce at three concentrations of plant material (14%, 25% and 50%), giving 36 mixes. Each mix was offered once to each of 20 male/female pairs of adult voles. Plant species that resulted in the lowest mean consumption were assumed to be the most repellent. Pachysandra (Pachysandra terminalis Sieb. and Zucc.), boxwood (Buxus sempervirens L.), daffodil (Narcissus pseudonarcissus L.), and crownvetch (Coronilla varia L.) were the best feeding deterrents at the lowest plant: applesauce concentration, and were among the most effective at the higher concentrations. At the lowest concentration (14%), mean intake of the plant/applesauce mix was 85% less with pachysandra than with the most preferred species, dandelion (Taraxicum officinalis Weber ex Wiggers).