Timothy R. Van Deelen

Temporal habitat partitioning and spatial use of coyotes and red foxes in East-Central Illinois

Coyote (Canis latrans) populations have increased across eastern North America over the past few decades. In Illinois, red fox (Vulpes vulpes) populations have synchronously declined, suggesting that coyotes may be displacing red foxes. We examined winter (Jan-Feb) and summer (Jul-Aug) habitat use of sympatric coyotes and red foxes in east-central Illinois, including a distinct urban fox population relatively free of interactions with coyotes. We radiomarked 28 coyotes, 16 rural foxes, and 19 urban foxes and systematically collected over 10,500 locations to infer habitat use. Compositional analysis at 3 levels (home range, location, resting) corresponded to 2 spatial scales of habitat use (study area and within home-range use). We used covariate analysis of regression models to examine interspecific differences in habitat use. Using Akaikes Information Criterion (AIC), optimal models included season, sex, and species of the covariate as sources of variation. Habitat partitioning was apparent at all levels of analysis during both seasons, diverging greatly during winter. Coyotes selected and rural foxes avoided cover-rich habitats (grassland, waterways, no-till corn). Rural foxes selected human-associated habitats (active and abandoned farmsteads and rural residential areas), which coyotes generally avoided. Habitat use and home-range selection by urban foxes were more seasonally stable than by rural foxes, but urban foxes selected residential areas more during winter than during summer. Home ranges of both coyotes and rural foxes increased substantially during winter. Rural fox home ranges were nearly 4 times larger than those of urban foxes during winter. Our study demonstrates that coyotes and sympatric red foxes partition habitat seasonally in response to a highly disturbed agricultural landscape. Farmland red foxes may avoid habitats used by sympatric coyotes, relying on human-associated habitats (farmsteads and urban areas) as refugia.

Survival and Movements of White-Tailed Deer in Suburban Chicago, Illinois

Management of high-density suburban deer populations requires knowledge of survival and movement to predict population trends. However, natural and human-induced influences on survival and movement of suburban deer are poorly understood. Therefore, we marked 208 (60 bucks, 148 does) white-tailed deer (Odocoileus virginianus) from forest preserves in Chicago, Illinois, USA (1994-1998). Seasonal and annual survivorship was >0.80 for 114 does and 13 bucks. Deer-auto collisions produced the highest mortality rates, 0.10 (95% CI 0.06 to 0.14) and 0.17 (95% CI 0.0 to 0.37). Spring dispersal for does was 7% (3 of 41) for fawns and 6% (5 of 83) for yearlings and adults; and for bucks it was 50% (8 of 16) for fawns and 7% (2 of 30) for yearlings and adults. All dispersals were <9 km, except for I parous doe that moved 33.9 km. Doe home ranges averaged 51 (95% CI 40.5 to 61.5), 26 (95% CI 22.0 to 30.0), and 32 (95% CI 19.6 to 44.4) ha for winter-spring, summer, and fall, respectively. A priori, we developed a set of 10 logistic regression models for suburban doe survival relative to home range size and traffic exposure indices. Using Akaikes Information Criterion (AIC), the best models included covariates reflecting home range size and traffic exposure. Inference across a ≥90% confidence set of survival models indicated substantial spatial heterogeneity in mortality risk for suburban does. High survival and philopatry by suburban deer apparently contribute to their overabundance in metropolitan areas.

Chronic Wasting Disease in Free-Ranging Wisconsin White-Tailed Deer

Three White-tailed Deer shot within 5 km during the 2001 hunting season in Wisconsin tested positive for chronic wasting disease, a prion disease of cervids. Subsequent sampling within 18 km showed a 3% prevalence (n=476). This discovery represents an important range extension for chronic wasting disease into the eastern United States.

Survival and Cause-Specific Mortality of Red Foxes in Agricultural and Urban Areas of Illinois

Abstract Range expansion and population increase by coyotes (Canis latrans), reduced hunting and trapping, and intensified agricultural practices in the Midwest have altered red fox (Vulpes vulpes) mortality, although relative impacts of these factors are unknown. We examined mortality causes and survival of red foxes in urban and rural agricultural areas of Illinois, using radio telemetry data from 335 foxes (Nov 1996 to May 2002). We used Akaikes Information Criterion to evaluate six survival models for foxes reflecting 1) environmental effects, 2) intrinsic effects, 3) temporal effects, 4) behavioral effects, 5) social effects, and 6) a global model. Environmental and intrinsic models of survival were optimal for adult foxes. Adult foxes with low (0–20%) and high (80–100%) percentages of row crops in their home ranges had higher survival than adults with moderate percentages (40–70%). Heavier adults at capture also survived better. A global model (all covariates) was optimal for juvenile foxes. Higher juvenile survival associated with larger litters, lower body fat, and reduced dispersal time. Yearly survival ranged from 0.18 for rural male juveniles to 0.44 for rural female adults. Adult survival rates (0.35) were 11% higher than juvenile survival rates (0.24). Yearly survival varied for urban foxes due to cyclic outbreaks of sarcoptic mange (Sarcoptes scabei). Thus, summer survival (May–Sep) of urban juveniles ranged from 0.10 (mange present) to 0.83 (no mange recorded). Mange was the most common (45% of all fatalities) source of mortality for urban foxes, followed by road kill (31%). We recorded only 4 mange fatalities (2%) for rural foxes. Rural foxes experienced low hunting mortality (7%) and equivalent road kill and coyote predation fatalities (40% each). Sources of mortality for midwestern foxes have dramatically changed since the 1970s when hunting was the major cause of mortality. Coyote predation has effectively replaced hunting mortality, and cyclic patterns of mange outbreaks in urban fox populations might indicate a dynamic source or sink relationship to surrounding rural fox populations. Absent mange, urban areas might provide refugia for red foxes where coyote populations persist at high densities in rural areas. Managers of sympatric urban and rural wildlife populations must understand survival dynamics influencing the population at the landscape level.

Effort and the Functional Response of Deer Hunters

Managers of overabundant deer have failed to incorporate relevant predator-prey theory into management research. In particular, understanding the functional response of deer hunters (deer encountered/time) to declining deer density is important because functional responses determine relative effort (time/deer encountered) required to harvest a deer and may, in turn, influence hunter perceptions of deer density and costs associated with deer removal. We used information-theoretic techniques and nonlinear regression to reanalyze data from controlled hunts in Illinois, Michigan, Wisconsin, and Ontario. Alternate models include killing rates or sighting rates as Type 1 (linear), Type 2 (hyperbolic), or Type 3 (sigmoidal) functions of deer density. Akaikes information criteria suggested that optimal models for most data sets were Type 1, although this may have been a artifact of small sample sizes. Nonetheless, effort curves derived from fitted functional responses indicated that relative effort accelerates as deer density declines. Accelerating effort requirements on the part of deer hunters likely hinders agency efforts to reduce overabundant deer populations and may be a source of hunter perceptions of unrealistically reduced deer herds. If general, this relation-ship (1) may determine what levels of harvest/removal are realistic, (2) is a potential source of bias in population estimation, and (3) may contribute to hunter distrust of agency efforts to reduce population size.

History, Population Growth, and Management of Wolves in Wisconsin

While we were growing up in Wisconsin during the 1950s and 1960s, gray wolves (we always called them timber wolves, Canis lupus) were making their last stand in northern Wisconsin. Wolves were considered a wilderness-dependant relic of Wisconsin’s frontier past that no longer belonged in our state. We did not expect wolves to ever again return to the state, at least not in any sizeable numbers. Among us, Dick Thiel was the most tenacious about trying to find evidence of wolves in Wisconsin, even as a student in the 1960s and 1970s. When wolves began returning during the mid-1970s, we dared not hope for any more than a token population of wolves to reestablish. The recovery of wolves in Wisconsin has succeeded beyond our wildest dreams. We have had the pleasure to document and track the amazing return of this powerful predator to our state.

Sex Affects Age Determination and Wear of Molariform Teeth in White-Tailed Deer

Field estimation of the ages of adult white-tailed deer (Odocoileus virginianus) and other ungulates often requires assessment of the degree to which molariform teeth wear over time. This widely used technlque is applied without regard to the sex of the animal being aged, but sex-based differences in ungulate life history traits such as diet, habitat use, and foraging behavior may affect tooth wear patterns differently for males and females. We examined sex-specific differences in tooth wear and morphology for adult (>1.5 yrs old) deer collected in northeastern Illinois (1993-97). We randomly sampled 100 mandibles from adult deer (50 M:50 F), stratified by cementum annuli year classes 2-7, to obtain 29 measurements of width, height, length, and visible dentine on premolars 2 and 4, and molars 1 and 3. Principle components (PC) analysis indicated that 61% of the overall sample variation was explained by PCs 1-3. Analysis using MANOVAs suggested effects (P < 0.05) due to sex and age when component scores from PCs 1-3 were used as dependent variables. Teeth from male deer were wider and tended to show more visible dentine (wear) on occlusal surfaces. Age class estimates of 10 experienced observers indicated substantial observer variation in the wear-replacement aging technique A repeated measures ANOVA indicated that sex effects in the wear-replacement aging technique become significant when the effects of observer variation are controlled. Stage-based projection models based on sex-specific age ratios of white-tailed deer had different growth rates and adult sex ratios when corrected for a sex bias in wear-replacement aging, indicating that common population analysis methods are sensitive to a sex-based bias. Managers should use caution when comparing adult age ratios derived from tooth wear because of potential sex biases in tooth wear patterns.

White-tailed deer management options model (DeerMOM): design, quantification, and application

Abstract The deer management options model (DeerMOM) is a computer simulation model designed to assess the effects of management options on population size, sex and age structure of white-tailed deer (Odocoileus virginianus). In this model, we grouped deer into three age classes: fawn, yearling, and adult. Reproductive rates and fetal sex ratios were age-specific, while natural and harvest mortality rates were both age- and sex-specific. DeerMOM was parameterized to represent the deer population in the Upper Peninsula of Michigan, USA. Effects of winter severity were incorporated into the model. Population estimates derived from annual pellet group surveys were used to validate the model. Different management options were evaluated using two criteria: a quantity goal (number of deer) and a quality goal (percentage of antlered bucks in the deer population). Simulation results indicated that current management practices (with a high rate of buck harvest) resulted in high deer numbers with a low percentage of antlered bucks. Under the condition of high buck harvest rate, increasing doe harvest did not achieve both the quantity and the quality goals simultaneously. Moderate harvest of both sexes would control population growth and increase the percentage of antlered bucks. The simulations also showed that winter weather conditions and doe harvest shaped deer population trends but buck harvest determined the percentage of antlered bucks. Our findings indicated that quality deer management objectives can be reached only by lowering buck harvest rates while simultaneously increasing the doe harvest. The best option for achieving both the quantity and the quality goals was moderate harvest of bucks and does without sex bias.

Alternative Feeding Strategies and Potential Disease Transmission in Wisconsin White-Tailed Deer

Abstract We conducted experimental feeding using 3 feeding methods (pile, spread, trough) and 2 quantities (rationed, ad libitum) of shelled corn to compare deer activity and behavior with control sites and evaluate potential direct and indirect transmission of infectious disease in white-tailed deer (Odocoileus virginianus) in central Wisconsin, USA. Deer use was higher at 2 of the feeding sites than at natural feeding areas (P ≤ 0.02). Deer spent a higher proportion of time (P < 0.01) feeding at pile (49%) and spread (61%) treatments than at natural feeding areas (36%). We found higher deer use for rationed than ad libitum feeding quantities and feeding intensity was greatest at rationed piles and lowest at ad libitum spreads. We also observed closer pairwise distances (≤0.3 m) among deer when corn was provided in a trough relative to spread (P = 0.03). Supplemental feeding poses risks for both direct and indirect disease transmission due to higher deer concentration and more intensive use relative to control areas. Concentrated feeding and contact among deer at feeding sites can also increase risk for disease transmission. Our results indicated that restrictions on feeding quantity would not mitigate the potential for disease transmission. None of the feeding strategies we evaluated substantially reduced the potential risk for disease transmission and banning supplemental feeding to reduce transmission is warranted.

Deer density and disease prevalence influence transmission of chronic wasting disease in white‐tailed deer

Host-parasite dynamics and strategies for managing infectious diseases of wildlife depend on the functional relationship between disease transmission rates and host density. However, the disease transmission function is rarely known for free-living wildlife, leading to uncertainty regarding the impacts of diseases on host populations and effective control actions. We evaluated the influence of deer density, landscape features, and soil clay content on transmission of chronic wasting disease (CWD) in young (<2-year-old) white-tailed deer (Odocoileus virginianus) in south-central Wisconsin, USA. We evaluated how frequency-dependent, density-dependent, and intermediate transmission models predicted CWD incidence rates in harvested yearling deer. An intermediate transmission model, incorporating both disease prevalence and density of infected deer, performed better than simple density- and frequency-dependent models. Our results indicate a combination of social structure, non-linear relationships between infectious contact and deer density, and distribution of disease among groups are important factors driving CWD infection in young deer. The landscape covariates % deciduous forest cover and forest edge density also were positively associated with infection rates, but soil clay content had no measurable influences on CWD transmission. Lack of strong density-dependent transmission rates indicates that controlling CWD by reducing deer density will be difficult. The consequences of non-linear disease transmission and aggregation of disease on cervid populations deserves further consideration.