Brent R. Patterson

Woodland Caribou Extirpation and Anthropogenic Landscape Disturbance in Ontario

Abstract The decline of woodland caribou (Rangifer tarandus caribou) has been attributed to anthropogenic landscape disturbances, but critical distance thresholds and time lags between disturbance and extirpation are unknown. Using a database of caribou presence and extirpation for northern Ontario, Canada, geo-coded to 10 × 10-km cells, we constructed logistic regression models to predict caribou extirpation based on distance to the nearest of each of 9 disturbance types: forest cutovers, fires, roads, utility corridors, mines, pits and quarries, lakes, trails, and rail lines. We used Akaikes Information Criterion to select parsimonious models and Receiver-Operating Characteristic curves to derive optimal thresholds. To deal with the effects of spatial autocorrelation on estimates of model significance, we used subsampling and restricted randomizations. Forest cutovers were the best predictor of caribou occupancy, with a tolerance threshold of 13 km to nearest cutover and a time lag of 2 decades between disturbance by cutting and caribou extirpation. Management of woodland caribou should incorporate buffers around habitat and requires long-term monitoring of range occupancy.

A review of methods to estimate cause-specific mortality in presence of competing risks

Abstract Estimating cause-specific mortality is often of central importance for understanding the dynamics of wildlife populations. Despite such importance, methodology for estimating and analyzing cause-specific mortality has received little attention in wildlife ecology during the past 20 years. The issue of analyzing cause-specific, mutually exclusive events in time is not unique to wildlife. In fact, this general problem has received substantial attention in human biomedical applications within the context of biostatistical survival analysis. Here, we consider cause-specific mortality from a modern biostatistical perspective. This requires carefully defining what we mean by cause-specific mortality and then providing an appropriate hazard-based representation as a competing risks problem. This leads to the general solution of cause-specific mortality as the cumulative incidence function (CIF). We describe the appropriate generalization of the fully nonparametric staggered-entry Kaplan–Meier survival estimator to cause-specific mortality via the nonparametric CIF estimator (NPCIFE), which in many situations offers an attractive alternative to the Heisey–Fuller estimator. An advantage of the NPCIFE is that it lends itself readily to risk factors analysis with standard software for Cox proportional hazards model. The competing risks–based approach also clarifies issues regarding another intuitive but erroneous “cause-specific mortality” estimator based on the Kaplan–Meier survival estimator and commonly seen in the life sciences literature.

Genetic nature of eastern wolves: Past, present and future

Eastern North American wolves have long been recognized as morphologically distinct from both coyotes and gray wolves. This has led to questions regarding their origins and taxonomic status. Eastern wolves are mainly viewed as: (1) a smaller subspecies of gray wolf (Canis lupus lycaon), potentially the result of historical hybridization between gray wolves (C. lupus) and red wolves (C. rufus), (2) a hybrid, the result of gray wolf (C. lupus) and coyote (C. latrans) interbreeding, or (3) a distinct species, C. lycaon, closely related to the red wolf (C. rufus). Although debate persists, recent molecular studies suggest that the eastern wolf is not a gray wolf subspecies, nor the result of gray wolf/coyote hybridization. Eastern wolves were more likely a distinct species, C. lycaon, prior to the eastward spread of coyotes in the late 1800s. However, contemporary interbreeding exits between C. lycaon to both C. lupus and C. latrans over much of its present range complicating its present taxonomic characterization. While hybridization may be reducing the taxonomic distinctiveness of C. lycaon, it should not necessarily be viewed as negative influence. Hybridization may be enhancing the adaptive potential of eastern wolves, allowing them to more effectively exploit available resources in rapidly changing environments.

Genetic differentiation of eastern wolves in Algonquin Park despite bridging gene flow between coyotes and grey wolves.

Distinguishing genetically differentiated populations within hybrid zones and determining the mechanisms by which introgression occurs are crucial for setting effective conservation policy. Extensive hybridization among grey wolves (Canis lupus), eastern wolves (C. lycaon) and coyotes (C. latrans) in eastern North America has blurred species distinctions, creating a Canis hybrid swarm. Using complementary genetic markers, we tested the hypotheses that eastern wolves have acted as a conduit of sex-biased gene flow between grey wolves and coyotes, and that eastern wolves in Algonquin Provincial Park (APP) have differentiated following a history of introgression. Mitochondrial, Y chromosome and autosomal microsatellite genetic data provided genotypes for 217 canids from three geographic regions in Ontario, Canada: northeastern Ontario, APP and southern Ontario. Coyote mitochondrial DNA (mtDNA) haplotypes were common across regions but coyote-specific Y chromosome haplotypes were absent; grey wolf mtDNA was absent from southern regions, whereas grey wolf Y chromosome haplotypes were present in all three regions. Genetic structuring analyses revealed three distinct clusters within a genetic cline, suggesting some gene flow among species. In APP, however, 78.4% of all breeders and 11 of 15 known breeding pairs had assignment probability of Q⩾0.8 to the Algonquin cluster, and the proportion of eastern wolf Y chromosome haplotypes in APP breeding males was higher than expected from random mating within the park (P<0.02). The data indicate that Algonquin wolves remain genetically distinct despite providing a sex-biased genetic bridge between coyotes and grey wolves. We speculate that ongoing hybridization within the park is limited by pre-mating reproductive barriers.

SOCIAL ORGANIZATION AND SPACE USE OF COYOTES IN EASTERN CANADA RELATIVE TO PREY DISTRIBUTION AND ABUNDANCE

Abstract We studied the influence of prey size and abundance on social organization and space use by eastern coyotes (Canis latrans) in 2 areas of Nova Scotia, Canada. Breeding pairs formed the nucleus of coyote social groups, and these often traveled with 1–3 other coyotes during winter. Increased use of white-tailed deer (Odocoileus virginianus) was insufficient to explain group size and cohesiveness by eastern coyotes. Winter-traveling group size was similar for family groups using deer (X̄ = 2.6) or snowshoe hares (X̄ = 2.7) as a primary prey in winter. Estimated densities of coyotes in winter was 4.3–13.9 coyotes/100 km2. Coyotes used the same general areas during winter and summer and from year to year. However, territory sizes decreased with increasing densities of deer (partial r2 = 0.21, P = 0.043) and hares (partial r2 = 0.40, P = 0.007). During winter, coyotes used areas of high deer density in proportion to their availability, but in some instances, they used areas that contained few or no deer proportionately more than expected, probably because deep snow and few trails increased vulnerability of deer in these areas. Territoriality seemed to prevent coyotes from concentrating in deer wintering areas and kept the coyote : deer ratio relatively low (<1:25).

Effects of Variable Sampling Frequencies on GPS Transmitter Efficiency and Estimated Wolf Home Range Size and Movement Distance

Abstract Global positioning system (GPS) technology has greatly improved the ability to investigate animal ecology at fine spatial and temporal scales but many GPS telemetry-based investigations may be underutilizing the technical capabilities of modern transmitters. We estimated eastern timber wolf (Canis lycaon) movement distance and territory size using variable GPS transmitter sampling frequencies to evaluate the effect of programming details on estimated movement patterns, territory size, and transmitter performance. Estimated movement distance decreased exponentially as sampling frequency was reduced from 1 location every 5 minutes to 1 location every 24 hours, implying that intense sampling frequencies were required for accurate measurement of fine-scale wolf movements. Wolf territory size estimates using 95% minimum convex polygons declined with decreasing sampling frequency, whereas estimates using adaptive kernel methods were comparable across a range of sampling intensities. Estimated transmitter battery longevity increased as the interval between fixes was lengthened but transmitter efficiency, defined as the number of successful fixes obtained during battery lifespan of the transmitter, was highest with fix intervals of intermediate length. Although GPS transmitters are effective for documenting fine-scale movements of animals, we argue their performance is strongly dependent upon transmitter programming and scale of analysis. Effective use of GPS transmitters will require study-specific assessment of the trade-offs between sampling needs versus transmitter efficiency and longevity.

Factors influencing killing rates of white-tailed deer by coyotes in eastern Canada

Predation affects the dynamics of many ungulate species. Until recently, little attention has been given to understanding the underlying processes and relationships in predator-prey systems. We examined factors affecting killing rates of white-tailed deer (Odocoileus virginianus) by coyotes (Canis latrans) in Nova Scotia, Canada. Snowshoe hare (Lepus americanus) and deer abundance, distribution and relative vulnerability of deer, and coyote group size all significantly influenced killing rates of deer by coyotes in winter. Groups of coyotes initiated proportionately more chases than single coyotes but chase success differed little among groups of 1-4 coyotes. Snow depth had a positive influence on success of pursuits. More kills were observed in areas of low deer density relative to areas with high deer densities. The mean distance of deer kills to recent clearcuts was significantly shorter than expected in an area where deer yarded during winter, but not in an area where deer did not aggregate during winter. Predator-prey ratios may not be a reliable indicator of predation rates of deer by coyotes because factors such as relative abundance and vulnerability of alternate prey, winter severity, and coyote social behavior also influence killing rates.

Spatial genetic and morphologic structure of wolves and coyotes in relation to environmental heterogeneity in a Canis hybrid zone

Eastern wolves have hybridized extensively with coyotes and gray wolves and are listed as a ‘species of special concern’ in Canada. However, a distinct population of eastern wolves has been identified in Algonquin Provincial Park (APP) in Ontario. Previous studies of the diverse Canis hybrid zone adjacent to APP have not linked genetic analysis with field data to investigate genotype‐specific morphology or determine how resident animals of different ancestry are distributed across the landscape in relation to heterogeneous environmental conditions. Accordingly, we studied resident wolves and coyotes in and adjacent to APP to identify distinct Canis types, clarify the extent of the APP eastern wolf population beyond the park boundaries and investigate fine‐scale spatial genetic structure and landscape–genotype associations in the hybrid zone. We documented three genetically distinct Canis types within the APP region that also differed morphologically, corresponding to putative gray wolves, eastern wolves and coyotes. We also documented a substantial number of hybrid individuals (36%) that were admixed between 2 or 3 of the Canis types. Breeding eastern wolves were less common outside of APP, but occurred in some unprotected areas where they were sympatric with a diverse combination of coyotes, gray wolves and hybrids. We found significant spatial genetic structure and identified a steep cline extending west from APP where the dominant genotype shifted abruptly from eastern wolves to coyotes and hybrids. The genotypic pattern to the south and northwest was a more complex mosaic of alternating genotypes. We modelled genetic ancestry in response to prey availability and human disturbance and found that individuals with greater wolf ancestry occupied areas of higher moose density and fewer roads. Our results clarify the structure of the Canis hybrid zone adjacent to APP and provide unique insight into environmental conditions influencing hybridization dynamics between wolves and coyotes.

Space‐use behaviour of woodland caribou based on a cognitive movement model

Movement patterns offer a rich source of information on animal behaviour and the ecological significance of landscape attributes. This is especially useful for species occupying remote landscapes where direct behavioural observations are limited. In this study, we fit a mechanistic model of animal cognition and movement to GPS positional data of woodland caribou (Rangifer tarandus caribou; Gmelin 1788) collected over a wide range of ecological conditions. The model explicitly tracks individual animal informational state over space and time, with resulting parameter estimates that have direct cognitive and ecological meaning. Three biotic landscape attributes were hypothesized to motivate caribou movement: forage abundance (dietary digestible biomass), wolf (Canis lupus; Linnaeus, 1758) density and moose (Alces alces; Linnaeus, 1758) habitat. Wolves are the main predator of caribou in this system and moose are their primary prey. Resulting parameter estimates clearly indicated that forage abundance is an important driver of caribou movement patterns, with predator and moose avoidance often having a strong effect, but not for all individuals. From the cognitive perspective, our results support the notion that caribou rely on limited sensory inputs from their surroundings, as well as on long-term spatial memory, to make informed movement decisions. Our study demonstrates how sensory, memory and motion capacities may interact with ecological fitness covariates to influence movement decisions by free-ranging animals.

Estimating wolf densities in forested areas using network sampling of tracks in snow

Abstract Few reliable methods exist for estimating population size of large terrestrial carnivores. This is particularly true in forested areas where sightability is low and when radiocollared individuals are unavailable in the target population. We used stratified network sampling to sample wolf (Canis lycaon) tracks in the snow to estimate density in western Algonquin Park, Ontario in February 2002. We partitioned our 3,425-km2 study area into 137 5 × 5-km sample units (SU) and stratified SUs as having a high (n = 61) or low (n = 76) probability of containing detectable wolf tracks based on the relative amount of watercourses and conifer cover within each block. We used a Bell 206B helicopter to survey 28 high (46%) and 17 low (22%) SUs. When fresh tracks were found in a block, we followed the tracks forward to the wolves themselves and then backward until the tracks were no longer considered “fresh.“ We observed 17 “fresh“ track networks within 45 SUs. The average pack size in the area we surveyed was 4.2 ± 0.4 (SE). These observations resulted in an estimate of 87 ± 11.4 (90% CI) wolves in the study area, for a density of 2.5 ± 0.3 wolves/100 km2. We detected no violations of the assumptions of this survey design and obtained a similar density estimate (2.3 wolves/100 km2) in 2003 using location data from 24 radiocollared wolves in 10 packs from an area that overlapped our 2002 survey area. The sampling unit probability estimator (SUPE) provides an objective, accurate, and repeatable means of estimating wolf density with an associated measure of precision. However, tracking wolves in forested cover was time-consuming, so costs will be considerably higher per unit area in forested areas relative to the more open cover types where this technique was originally developed.