Gray Wolves (Canis lupus) consume free-ranging horses (Equus ferus caballus) on the Chilcotin plateau, British Columbia

We analyzed 122 Gray Wolf (Canis lupus) scats, collected at all seasons during 2013–2017, to determine what wolves were eating in two adjacent study areas of the Chilcotin region, British Columbia: Brittany Triangle and Nemiah Valley. Free-ranging horses (Equus ferus caballus), Mule Deer (Odocoileus hemionus), Moose (Alces americanus), and small mammals contributed to wolf diet throughout the year. In both study areas, horse appeared more frequently than other species in occurrence-per-faeces (OF) and occurrence-per-item (OI) analyses. Horse occurred in 58 of 97 wolf scats from Brittany (OF 59.8%, OI 52.7%), deer in 26 (OF 26.8%, OI 23.6%), small mammals in 17 (OF 17.5%, OI 17.3%), Moose in four (OF 4.1%, OI 3.6%), and bird and fish minimally (both OF <2.5%, OI <2.5%). The sample size in the more human-developed Nemiah Valley was too small to estimate reliable patterns, but results suggest a similar ranking of dietary items. Domestic Cattle (Bos taurus), available in both study areas, appeared infrequently (combined area OF <3.5%, OI <3.0%). Based on our scat findings, free-ranging horses were a regular dietary item for wolves in the area. Studies elsewhere have found that, where wolves and free-ranging horses are sympatric, a predator–prey relationship exists

The Effect of Fire on Spatial Separation Between Wolves and Caribou

Fire management is an important conservation tool in Canada’s national parks. Fires can benefit some species, while others may be negatively impacted. We used GPS and VHF collar data for 47 wolves from 12 separate packs and 153 caribou from 5 separate herds, and resource selection analysis to model the effects of fire on these species’ habitat and potential interactions. Resource selection modeling showed that wolves select for burned areas and areas close to burns, presumably due to the presence of primary prey (i.e., elk and moose), while caribou avoid burns. Fire reduced the amount of high quality caribou habitat (a direct effect), but also increased the probability of wolf-caribou overlap (an indirect effect). We delineated a spatial index of caribou “safe zones” (areas of low overlap with wolves), and found a positive relationship between the proportion of a herd’s home range represented by “safe zone” in winter and population size (P = 0.10, n=4). While currently-planned prescribed fires in Banff and Jasper reduced the amount of quality caribou habitat by up to 4%, they reduced the area of “safe zones” by up to 7%, varying by herd, location, and season. We suggest that conservation managers should account for the indirect, predator-mediated impacts of fire on caribou in addition to direct effects of habitat loss

Transcending Scale Dependence in Identifying Habitat with Resource Selection Functions

Multi-scale resource selection modeling is used to identify factors that limit species distributions across scales of space and time. This multi-scale nature of habitat suitability complicates the translation of inferences to single, spatial depictions of habitat required for conservation of species. We estimated resource selection functions (RSFs) across three scales for a threatened ungulate, woodland caribou (Rangifer tarandus caribou), with two objectives: (1) to infer the relative effects of two forms of anthropogenic disturbance (forestry and linear features) on woodland caribou distributions at multiple scales and (2) to estimate scale-integrated resource selection functions (SRSFs) that synthesize results across scales for management-oriented habitat suitability mapping. We found a previously undocumented scale-specific switch in woodland caribou response to two forms of anthropogenic disturbance. Caribou avoided forestry cut-blocks at broad scales according to first-and second-order RSFs and avoided linear features at fine scales according to third-order RSFs, corroborating predictions developed according to predator-mediated effects of each disturbance type. Additionally, a single SRSF validated as well as each of three single-scale RSFs when estimating habitat suitability across three different spatial scales of prediction. We demonstrate that a single SRSF can be applied to predict relative habitat suitability at both local and landscape scales in support of critical habitat identification and species recovery

A Primary Productivity Hypothesis for Disturbance-Mediated Apparent Competition for Boreal Caribou in Canada

The most widely reported threat to populations of boreal and mountain woodland caribou (Rangifer tarandus caribou) involves what has come to be known as disturbance-mediated apparent competition (DMAC). Here, anthropogenic and natural disturbances that increase the abundance of deciduous-browsing cervids (e.g., moose [Alces alces] and white-tailed deer [Odocoileus virginianus]) are thought to promote predator (especially wolf [Canis lupus]) numbers, in turn heightening predation risk to caribou. We know most about the hypothesis of DMAC as it relates to caribou where the species is under threat by industry; i.e., from relatively productive southern boreal and mountain systems where landscapes are highly managed and multiple species of predators and ungulate prey interact with caribou. Yet almost 2/3 of extant boreal caribou range occurs in poorly productive, wildfire-dominated areas where caribou compete with only one ungulate species (moose) in the context of DMAC. In Ch. 2, using data specific to the Saskatchewan Boreal Shield, I tested for evidence of DMAC with data specific to an area of previously known low primary productivity. I found that the successional dynamics after fire of the low-productivity boreal shield did not allow for flushes in deciduous browse, meaning moose density could not increase and resulting in no evidence for DMAC in this system. To test predictions consistent with DMAC, in Ch. 3, I examined the relationship between net primary productivity (NPP) with calf recruitment and adult female survival at a national scale. I accounted for variables influencing DMAC, including metrics of large mammal richness, alternative prey biomass, and predator biomass. While geographic site played an important role, NPP was the most important variable in beta regressions, visually influenced PCA dimensionality in the dataset, and was a primary causal factor for reduced caribou survival and recruitment in Structural Equation Models (SEM). The results indicate that NPP and anthropogenic disturbance act as an impetus for DMAC, where the phenomenon is unlikely to occur in low-productivity areas. Overall, I postulate that the DMAC phenomenon is dependent on NPP, or energy in the system, where burned areas of low NPP may not create the conditions necessary for DMAC to occur. Understanding what factors influence where DMAC occurs and at what scale will be critical for determining effective conservation strategies for local caribou range-planning and Canada’s federal Recovery Strategy for boreal caribou

Resource selection and abundance estimation of moose: Implications for caribou recovery in a human altered landscape

Woodland caribou (Rangifer tarandus caribou) are threatened across Canada due to human disturbance altering predator-prey dynamics. The niche specialization of caribou enables them to survive in nutrient-poor habitats spatially separated from other ungulates and their shared predators. The conversion of old-growth forests to young seral stands is hypothesized to increase the abundance of moose (Alces alces), the dominant prey for wolves (Canis lupus), resulting in apparent competition. We first examined habitat selection of moose in 2 regions with differing intensities of human disturbance in west-central Alberta and east-central British Columbia to assess how human disturbance affects the spatial separation of moose and caribou. We built resource selection functions with data from global positioning system (GPS) collars deployed on 17 moose (8 in a region with high and 9 in a region with low human disturbance) at 2 spatial scales. Our results indicated that moose in our study area make forage-risk tradeoffs in a hierarchical fashion similar to caribou, potentially eroding spatial separation in human disturbed landscapes. We also evaluated the spatial partitioning of resources by comparing resource use with GPS locations from 17 moose and 17 paired caribou using logistic regression. As expected, human disturbance decreased the resource partitioning between moose and caribou. Thus, systematic moose management and monitoring will be essential for caribou conservation. Currently, a Stratified Random Block (SRB) survey design is widely used to estimate moose populations, but these surveys are expensive and often result in imprecise population estimates when not corrected for sightability bias. We evaluated the application of distance sampling as an alternative to SRB surveys, especially for use in caribou ranges. To correct for moose missed on the transect line, where a detection rate of 100% is critical, we developed a sightability model using 21 radio-collared moose. After correcting for sightability, distance sampling was more precise and efficient than SRB surveys. In this way, more efficient distance sampling methodology can be an important tool for caribou conservation. Combined, our results showed the importance of moose management in caribou ranges due to decreased spatial separation between both ungulate species in disturbed landscapes

Land management strategies for the long-term persistence of boreal woodland caribou in central Saskatchewan

We investigated landscape changes and their potential effects on woodland caribou-boreal ecotype (Rangifer tarandus caribou) within a portion of the Smoothstone-Wapaweka Woodland Caribou Management Unit (SW-WCMU). The SW-WCMU is one of eight areas delineated by the Province of Saskatchewan for potential recovery planning efforts for boreal caribou, and is one of four management units located on the Boreal Plain Ecozone. The Prince Albert Greater Ecosystem (PAGE) study area was selected within the SW-WCMU for intensive study from 2004 - 2008. Studies focused on quantifying a suite of landscape and population parameters. This paper presents a summary of study results to date and recommends land management strategies intended to contribute to the long-term viability of boreal caribou in the central boreal plain ecoregion of Saskatchewan. The PAGE study area has undergone structural changes from an area that historically presented a lesser amount but well connected mature coniferous forest, to a currently larger amount of mature coniferous stands fragmented by a highly developed network of roads and trails. Movement data pointed to highly clustered use of the landscape by small groups of caribou and smaller home ranges when compared to 15 years ago. Calving sites were located within each individual home range in treed peatland and distant from hardwood/mixedwood forest stands, roads and trails access. Adult annual survival rates were low, averaging 73% over the course of the study. In order to ensure a self-sustaining population level, study results clearly point to the need for landscape restoration to reduce the level of anthropogenic disturbances in some key parts of the study area. Key strategies include retention of mature softwood forest interior proximate to local areas of caribou activity, protection of calving habitat, improving structural connectivity, planning disturbances (forest harvesting, fire salvage, resource exploration, access development) in ways to minimize the anthropogenic footprint, and recovery action planning integrated with other land-use planning initiatives

UNGULATES SEARCH FOR THE IDEAL HOME: HOW PREDATION AND FORAGE DIFFERENTIALLY AFFECT MALES AND FEMALES IN A PARTIALLY MIGRATORY POPULATION

Migration is a strategy used across taxa to access resources in temporally heterogenous landscapes. Migratory species can attain higher abundances because access to higher quality resources, and/or reduction in predation risk. However, most migratory species occur in partially migratory populations, a mix of migratory and non-migratory, resident individuals. I first investigate the potential mechanisms maintaining partial migration in a partially migratory elk (Cervus canadensis) population. I test whether the theory of Ideal Free Distribution (IFD) can explain the coexistence of different migratory tactics in a partially migratory population. IFD predicts that individuals exhibit density-dependent vital rates and should select different migratory tactics to maximize individual fitness, resulting in equal fitness () between tactics. We found density dependent pregnancy and adult female survival for residents, providing a fitness incentive to switch tactics. Despite differences in vital rates between tactics, mean λ (fitness) was equal, as predicted by IFD, because individual females switched tactics toward those of higher fitness. Next, I tested the Reproductive Strategy Hypothesis (RSH) for sexual segregation in the context of partial migration. I compared males and females for differences in their use and selection for forage and predation risk across spatiotemporal scales. I found support for the RSH as males adopted the migratory tactic with the highest forage quality and used higher quality forage than females. In summer, females avoided the primary predator of neonate calves further supporting the RSH, but potentially at the expense of increased exposure to wolf predation risk. Antler growth and development was driven by age and forage quality, and because migration increased forage quality, migration likely benefits male reproductive success, also supporting the RSH. Finally, I investigated the effect of age, forage, predation and harvest on male elk survival. Male elk survival was largely a function of age, as human harvest was the primary cause of mortality and antler-point-restrictions resulted in low survival for male elk over 4 years of age (S=0.42). My work demonstrates ecological drivers of population dynamics of partially migratory ungulates that has global relevance given recent declines in migratory large ungulate populations and migratory routes

ESTIMATING WOLF PREDATION METRICS, PATTERNS, AND DYNAMICS ACROSS TIME AND SPACE IN THE MULTI-PREY SYSTEM OF YELLOWSTONE NATIONAL PARK

Predation is a fundamental driver in ecology, structuring ecosystems across the globe. However, understanding the effects of large carnivore predation is limited by both the observation process and the shorter duration of many studies. I used data from 23 years in Yellowstone National Park to disentangle both the importance of wolf predation on prey, and the imperfect observation process of studying predation. I first used field observations to test whether a sexually-selected trait, antlers in male elk, deterred wolf predation. I found that antlers reduced predation risk, emphasizing the selective nature of predation. Next, I used GPS data and ground-based observations to develop wolf sightability models to understand the nature of wolf sightings. I found forest cover, distance from road, topography, and wolf group size affected the probability of observing wolves. Next, I leveraged my sightability model to develop a Bayesian markrecapture abundance model that estimated the number of ungulates fed on by wolf packs during study sessions. I built a model for carcass detection by ground-based observation, aerial-based observation, and GPS cluster searches. Overlooking all details, field methods found only 47% of the estimated occasions when wolf packs fed on ungulates. Using these detection-corrected estimates to evaluate how six wolf predation metrics differed through time as elk declined and stabilized and bison increased, I found that wolf predation on elk generally declined concurrent with the elk decline. I also found that wolf diet (niche) breadth expanded over time primarily by scavenging bison. Though generalizing was challenging, using the simple metric of predation rate, I found predation rate was inversely density dependent in winter on just the wintering elk population within northern Yellowstone National Park. However, wolf predation was conversely a stabilizing force when considering annual predation rate on the entire northern Yellowstone elk population. These observations are consistent with wolves acting as a stabilizing, regulating force on the northern Yellowstone elk population. Finally, I built theoretical models guided by my observations of the wolf-elk-bison system in northern Yellowstone to evaluate how scavenging affects predator-prey dynamics. I found that including scavenging fundamentally changes dynamics, generally increasing prey and predator populations

Wolf Predation: Where and How Wolves Kill Beavers, and Confronting the Biases in Scat-Based Diet Studies

Beavers can be a significant prey item for wolves in boreal systems but how wolves hunt beavers is largely unknown. I inferred how wolves hunt beavers by identifying 22 kill sites using clusters of locations from GPS-collared wolves in Voyageurs National Park, Minnesota. Where wolves killed beavers varied seasonally with the majority (58%) of kills in the spring occurring below dams and on shorelines while the majority (80%) of kills in the fall were near feeding trails and canals. I deduced that the typical hunting strategy has 3 components: 1) waiting near areas of high beaver use until a beaver comes near or on shore, 2) using concealment, and 3) immediately attacking the beaver, or ambushing the beaver by cutting off access to water. Wolf diet is commonly estimated via scat analysis, and several studies have concluded that scat collection method can bias diet estimates. I tested whether different scat collection methods yield different diet estimates after accounting for other biases. I collected scats (2,406 scats) monthly from 4 packs via 3 scat collection methods in the Voyageurs National Park, Minnesota area, during April 2015–October 2015. Scat collection method did not yield different diet estimates but I did document temporal, inter-pack, and age class variability in diet estimates. To better estimate wolf population diets, researchers should collect ≥10–20 adult scats/pack/month from homesites and/or opportunistically from packs that are representative of the population of interest

Environmental and anthropogenic drivers of connectivity patterns: A basis for prioritizing conservation efforts for threatened populations

Ecosystem fragmentation and habitat loss have been the focus of landscape management due to restrictions on contemporary connectivity and dispersal of populations. Here, we used an individual approach to determine the drivers of genetic differentiation in caribou of the Canadian Rockies. We modelled the effects of isolation by distance, landscape resistance and predation risk and evaluated the consequences of individual migratory behaviour (seasonally migratory vs. sedentary) on gene flow in this threatened species. We applied distance‐based and reciprocal causal modelling approaches, testing alternative hypotheses on the effects of geographic, topographic, environmental and local population‐specific variables on genetic differentiation and relatedness among individuals. Overall, gene flow was restricted to neighbouring local populations, with spatial coordinates, local population size, groups and elevation explaining connectivity among individuals. Landscape resistance, geographic distances and predation risk were correlated with genetic distances, with correlations threefold higher for sedentary than for migratory caribou. As local caribou populations are increasingly isolated, our results indicate the need to address genetic connectivity, especially for populations with individuals displaying different migratory behaviours, whilst maintaining quality habitat both within and across the ranges of threatened populations