Anthropogenic Disturbance and Population Viability of Woodland Caribou in Ontario

One of the most challenging tasks in wildlife conservation and management is to clarify how spatial variation in land cover due to anthropogenic disturbance influences wildlife demography and long-term viability. To evaluate this, we compared rates of survival and population growth by woodland caribou (Rangifer tarandus caribou) from 2 study sites in northern Ontario, Canada that differed in the degree of anthropogenic disturbance because of commercial logging and road development, resulting in differences in predation risk due to gray wolves (Canis lupus). We used an individual-based model for population viability analysis (PVA) that incorporated adaptive patterns of caribou movement in relation to predation risk and food availability to predict stochastic variation in rates of caribou survival. Field estimates of annual survival rates for adult female caribou in the unlogged ( 0.90) and logged ( 0.76) study sites recorded during 2010–2014 did not differ significantly (P > 0.05) from values predicted by the individual-based PVA model (unlogged: = 0.87; logged: 0.79). Outcomes from the individual-based PVA model and a simpler stage-structured matrix model suggest that substantial differences in adult survival largely due to wolf predation are likely to lead to long-term decline of woodland caribou in the commercially logged landscape, whereas the unlogged landscape should be considerably more capable of sustaining caribou. Estimates of population growth rates (λ) for the 2010–2014 period differed little between the matrix model and the individual-based PVA model for the unlogged (matrix model = 1.01; individual-based model = 0.98) and logged landscape (matrix model = 0.88; individual-based model = 0.89). We applied the spatially explicit PVA model to assess the viability of woodland caribou across 14 woodland caribou ranges in Ontario. Outcomes of these simulations suggest that woodland caribou ranges that have experienced significant levels of commercial forestry activities in the past had annual growth rates <0.89, whereas caribou ranges that had not experienced commercial forestry operations had population growth rates >0.96. These differences were strongly related to regional variation in wolf densities. Our results suggest that increased wolf predation risk due to anthropogenic disturbance is of sufficient magnitude to cause appreciable risk of population decline in woodland caribou in Ontario. © 2020 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Disturbance-Mediated Apparent Competition Decouples in a Northern Boreal Caribou Range

The most widely reported threat to boreal and mountain populations of woodland caribou (Rangifer tarandus caribou; caribou) involves habitat- or disturbance-mediated apparent competition (DMAC). With DMAC, natural and anthropogenic disturbances that increase the abundance of deciduous-browsing cervids (e.g., moose [Alces alces], deer [Odocoileus spp.]) are thought to promote predator (especially wolf [Canis lupus]) numbers, which heightens predation risk to caribou. We know most about the effects of DMAC on caribou where the species is under threat by anthropogenic activities in relatively productive southern boreal and mountain systems. Yet, >60% of extant boreal caribou range in North America consists of northern shield and taiga ecoregions of low productivity where caribou may compete with only 1 ungulate species (moose) in the context of DMAC. In this environment, we know very little of how DMAC acts as a limiting factor to caribou. In Saskatchewan, Canada, from 2014–2018, using a combination of vegetation sampling, aerial surveys, and telemetry data (n = 38 wolves), we searched for evidence of DMAC (trends in data consistent with the hypothesis) in an 87,193-km² section of the Western Boreal Shield, a poorly productive but pristine region (0.18% of land cover classed as an anthropogenic feature) with a historically high fire-return interval (47% of stands aged <40 years). Despite the high levels of disturbance, moose density was relatively low (47 moose/1,000 km²), likely because of the scarcity of deciduous or mixed-wood stands and low abundance of deciduous browse in the young conifer stands that dominated the landscape. In contrast, boreal caribou density was relatively high for the species (37 caribou/1,000 km²). Wolf density (3.1 wolves/1,000 km²) and pack sizes ( = 4.0 wolves/pack) were low and resident (established) territories were large ( = 4,360 km²; 100% minimum convex polygon). The low density of wolves mirrored the low (standardized) ungulate biomass index (UBI; moose + boreal caribou) of the study area (0.36 UBI/km²). We conclude that wolf and hence caribou populations were not responding in accordance with the outcomes generally predicted by DMAC in our study area because the requisite strong, positive response to fire of deciduous-browse and alternate-prey abundance was lacking. As a limiting factor to caribou, DMAC is likely modulated at a macroecological scale by factors such as net primary productivity, a corollary to the general hypothesis that we advance here (i.e., primary productivity hypothesis of DMAC). We caution against managing for caribou based on the presumption of DMAC where the mechanism does not apply, which may include much of boreal caribou range in the north. © 2020 The Wildlife Society.     

Evidence for Depressed Reproduction of Golden Eagles in Washington

Beginning in 1977 the Washington Department of Fish and Wildlife conducted annual surveys to determine statewide golden eagle (Aquila chrysaetos) occupancy and productivity. Current interest in the regional and national status of the species prompted our investigation to determine utility of historical data in assessing trends in reproduction, and to test efficacy of a sampling protocol that surveyed randomly selected territories and also accounted for detection probability. We found evidence indicating poor reproduction from 38 annual surveys conducted at 301 known territories statewide between 1977 and 2014. At 256 territories in eastern Washington, USA, apparent occupancy was low ( = 50.9%) and nesting success declined by 22%. All reproductive parameters were higher than at 45 territories in western Washington. We tested efficacy of a sampling protocol in 2013 and 2014 by surveying 108 randomly selected eastern territories. Probability of detecting eagles for these years from ground (= 89%) was greater than from air (= 66%). Our estimate of territory occupancy, corrected by probability of detection, was lower in 2013 (= 56.7%, 95% CI = 46.3–66.7%) than in 2014 (= 73.7%, 95% CI = 64.8–81.7%), as was the estimated number of breeding pairs (2013: = 158, 95% CI = 151–164; 2014: = 187, 95% CI = 182–192). Higher productivity (young/occupied territory) in 2013 (= 0.59, 95% CI = 0.40–0.82) than in 2014 (= 0.41, 95% CI = 0.27–0.59) and lower proportions of ≥1 immature eagle among nesting pairs in 2013 (16%) than in 2014 (31%), suggested higher immature pairing among sampled pairs contributed to inter-year differences in these reproductive parameters. Current and historical evidence for depressed golden eagle nesting in Washington is consistent with documented effects from habitat conversion, prey declines, lead contamination, and wind power development. We recommend future surveys in eastern Washington adhere to the random sampling protocol and conduct surveys at regular intervals to allow for trend analysis of reproductive parameters to better monitor golden eagle status. Surveys in western Washington, conducted exclusively from ground at all nests, will improve detection and cost efficiency. © 2020 The Wildlife Society.     

Optimal Strategies for Managing Wildlife Harvest Under System Change

Wildlife populations are experiencing shifting dynamics due to climate and landscape change. Management policies that fail to account for non-stationary dynamics may fail to achieve management objectives. We establish a framework for understanding optimal strategies for managing a theoretical harvested population under non-stationarity. Building from harvest theory, we develop scenarios representing changes in population growth rate () or carrying capacity () and derive time-dependent optimal harvest policies using stochastic dynamic programming. We then evaluate the cost of falsely assuming stationarity by comparing the outcomes of forward projections in which either the optimal policy or a stationary policy is applied. When declines over time, the stationary policy leads to an underharvest of the population, resulting in less harvest over the short term but leaving the population in a higher-value state. When declines over time, the stationary policy leads to overharvest, resulting in greater harvest returns in the short term but leaving the population in a lower and potentially more vulnerable state. This work demonstrates the basic properties of time-dependent harvest management and provides a framework for evaluating the many outstanding questions about optimal management strategies under climate change. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.     

Genetic Characteristics of Restored Elk Populations in Kentucky

Translocations are a common management practice to restore or augment populations. Understanding the genetic consequences of translocation efforts is important for the long-term health of restored populations. The restoration of elk (Cervus canadensis) to Kentucky, USA, included source stocks from 6 western states, which were released at 8 sites in southeastern Kentucky during 1997–2002. We assessed genetic diversity in restored herds and compared genetic similarity to source stocks based on 15 microsatellite DNA loci. Genetic variation in the restored populations was comparable to source stocks ( allelic richness = 3.52 and 3.50; expected heterozygosity = 0.665 and 0.661 for restored and source, respectively). Genetic differentiation among all source and restored populations ranged from 0.000 to 0.065 for pairwise F_ST and 0.034 to 0.161 for pairwise Nei's D_A. Pairwise genetic differentiation and Bayesian clustering revealed that stocks from Utah and North Dakota, USA, contributed most to restored populations. Other western stocks appeared less successful and were not detected with our data, though our sampling was not exhaustive. We also inferred natural movements of elk among release sites by the presence of multiple genetic stocks. The success of the elk restoration effort in Kentucky may be due, in part, to the large number of elk (n = 1,548), repeated releases, and use of diverse source stocks. Future restoration efforts for elk in the eastern United States should consider the use of multiple stock sources and a large number of individuals. In addition, preservation of genetic samples of founder stock will enable detailed monitoring in the future. © 2020 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Prey Specialization by Cougars on Feral Horses in a Desert Environment

Natural controls on the distribution, abundance, or growth rates of exotic species are a desirable mode of intervention because of lower costs compared to anthropogenic controls and greater social acceptance. In the Great Basin, cougars (Puma concolor) are the most widely distributed carnivore capable of killing large ungulate prey. Populations of feral horses (Equus ferus) are widely distributed throughout the Great Basin and can grow at rates up to 20%/year. Although cougars exhibit distributional overlap with horses, it has been assumed that predation is minimal because of differences in habitat use and body-size limitations. To evaluate this hypothesis, we monitored the diets of 21 global positioning system (GPS)-collared cougars in the western Great Basin (5 males, 8 females) and eastern Sierra Nevada (2 males, 6 females) from 2009–2012. We investigated 1,310 potential kill sites and located prey remains of 820 predation events. We compared prey composition and kill rates of cougars inhabiting the Sierra Nevada and Great Basin, and among male and female cougars across seasons. We used generalized linear mixed models (GLMMs) to examine the effects of prey availability and habitat characteristics on the probability of predation on horses by cougars. Mule deer (Odocoileus hemionus) comprised 91% of prey items killed on the Sierra Nevada reference site but only comprised 29% of prey items in the Great Basin study area. Average annual kill rates for deer differed between the Sierra Nevada ( = 0.85 deer/week, range = 0.44–1.3) and Great Basin ( = 0.21 deer/week, range = 0.00–0.43). Diets of cougars in the Great Basin were composed predominantly of horses (59.6%, n = 460 prey items; 13 individuals). Ten cougars regularly consumed horses, and horses were the most abundant prey in the diet of 8 additional individuals in the Great Basin. Cougars on average killed 0.38 horses/week in the Great Basin (range=0.00–0.94 horses/week). Differences in predation on horses between the sexes of cougars were striking; Great Basin females incorporated more horses across all age classes year-round, whereas male cougars tended to exploit neonatal young during spring and summer before switching to deer during winter. Within GLMM models, the probability of predation on horses compared to other prey species increased with elevation, horse density, and decreasing density of mule deer on the landscape, and was more likely to occur in sagebrush (Artemesia spp.) than in pinyon (Pinus monophylla)–juniper (Juniperus osteosperma) forests. Behavior of individual cougars accounted for more than a third of the variation explained by our top models predicting predation on horses in the Great Basin. At landscape scales, cougar predation is unlikely to limit the growth of feral horse populations. In the Great Basin ecosystem, however, cougars of both sexes successfully preyed on horses of all age classes. Moreover, some reproductive, female cougars were almost entirely dependent on feral horses year-round. Taken together, our data suggest that cougars may be an effective predator of feral horses, and that some of our previous assumptions about this relationship should be reevaluated and integrated into management and planning. © 2021 The Wildlife Society.     

Bobcat Hair Cortisol Correlates with Land Use and Climate

Bobcats (Lynx rufus) have been increasing in abundance in the northeast United States despite a corresponding trend of increased anthropogenic land uses. Inhabiting areas of high human land use can affect stress levels, and hence cortisol titers, for wildlife species by increasing frequency of human interaction and altering habitats. In turn, increased cortisol levels can have negative effects at the individual and population level including decreased immune function, slowed growth and tissue repair, reduced reproductive capacity, and nutritional deficiencies. We quantified cortisol in bobcats across New Hampshire and Vermont, USA, using hair samples, then explored associations between hair cortisol and various organismal, land use, land cover, and climatic variables at 2 different spatial scales. Hair cortisol differed by season and bobcat mass. On average, cortisol levels were higher in fall than in spring, and larger bobcats had lower cortisol levels. Anthropogenic land uses—especially residential and agricultural uses—were the most important predictors of hair cortisol at the town scale ( area = 93 km²). At a larger scale (Wildlife Management Units; area = 1,256 km²), temperature and precipitation were better predictors of hair cortisol, suggesting that extreme weather may have significant effects on bobcat population dynamics. Our results highlight the importance of landscape composition and local conditions in the sustainable management of furbearer populations. © 2021 The Wildlife Society.     

Assessing Population Viability of Black Bears using Spatial Capture-Recapture Models

The Central Georgia Bear Population (CGP) is the least abundant and most isolated of Georgia's 3 American black bear (Ursus americanus) populations. Beginning in 2011, changes to regulations governing harvest of the CGP resulted in an increase in female bear harvest, creating concern that future harvest could be an important influence on population viability. Hence, our objective was to assess viability of the CGP under various levels of female mortality. During 2012–2016, we used barbed-wire hair snares to collect bear hair samples from within the range of the CGP in Georgia, USA. We used microsatellite genotyping to identify individual bears and created robust-design, spatial detection histories for all female bears detected. We fit open population spatial capture-recapture (SCR) models to the detection histories in a Bayesian framework. We used the Widely Applicable Information Criterion (WAIC) to rank models that varied with respect to sources of variation in detection probability, survival, and per capita recruitment, and used the model with the lowest WAIC to forecast dynamics of the CGP 50 years into the future under various levels of female mortality. We assessed the 50-year extinction probability under a continuation of mortality levels documented during 2012–2016, and under incremental increases in female mortality above this baseline. The top model included density-dependent per capita recruitment, annual variation in detection probability, and a trap-level behavioral response. Abundance increased from 106 (95% CI = 86–132) females in 2012 to 136 (95% CI = 113–161) females in 2013 and remained relatively stable thereafter. Annual female survival was 0.75 (95% CI = 0.69–0.82) and did not vary among years. The per capita recruitment rate decreased over time as density increased, and was 0.49 (95% CI = 0.33–0.66) during the first time interval and 0.29 (95% CI = 0.20–0.38) during the final time interval. Annual growth rate () was 1.28 (95% CI = 1.07–1.52) between 2012 and 2013 but decreased throughout the study, ending at 1.04 (95% CI = 0.93–1.17). Forecasts indicated continuation of the female mortality levels experienced from 2012–2016 were sustainable over 50 years, with the estimated extinction risk being <0.001%. Increasing annual harvest by 5 females introduced a negligible increase in the 50-year probability of extinction, but harvesting an additional 10 females/year caused extinction risk to rise to 1.15%. We recommend that harvest regulations are structured such that mortality rates remain at current levels or do not increase by more than an annual average of 5 females above levels observed during our study. Furthermore, we recommend that managers continue to monitor the population so that harvest regulations and population models can be refined over time. © 2020 The Wildlife Society.     

Evaluating risks associated with capture and handling of mule deer for individual-based,long-term research

Capture and handling techniques for individual-based, long-term research that tracks the life history of animals by recapturing the same individuals for several years has vastly improved study inferences and our understanding of animal ecology. Yet there are corresponding risks to study animals associated with physical trauma or capture myopathy that can occur during or following capture events. Rarely has empirical evidence existed to guide decisions associated with understanding the magnitude of capture-related risks, how to reduce these risks when possible, and implications for mortality censoring and survival estimates. We used data collected from 2,399 capture events of mule deer (Odocoileus hemionus) via helicopter net-gunning to compare daily survival probabilities within a 10-week period centered on a capture event and evaluated how animal age, nutritional condition (body fat), and various handling methods influenced survival before, during, and following a capture event. Direct mortality resulting from capture efforts was 1.59%. Mean daily survival was 0.9993 ± 0.0001 (SE) during the 5-week pre-capture window, was depressed the day of capture at 0.9841 ± 0.0004, and rebounded to 0.9990 ± 0.0008 during the 5-week post-capture window. Neither capture nor handling had a detectable effect on post-capture survival, including handling time ($\overline{x}$ = 13.30 ± 1.87 min), capture time of year (i.e., Dec or Mar), tooth extraction, and the number of times an animal had been recaptured (2–17 times). Although mortality rate was slightly elevated during capture (resulting from physical trauma associated with capture), age and nutritional condition did not influence the probability of mortality during a capture event. Following a capture event, nutritional condition influenced survival; however, that relationship was consistent with expected effects of nutritional condition on winter survival and independent of capture and handling. Overall survival rates 5 weeks before capture and 5 weeks after capture were not different. A specified window of time with depressed survival following capture and handling was not evident, which contradicts the implementation of a predetermined window often used by researchers and managers for censoring mortalities that occur after capture. Previous notions that censorship of all mortality data in the 2 weeks following capture is unwarranted and risks removal of meaningful data. With previous evidence guiding our protocols for capture (e.g., reduced chase time) and handling (e.g., temperature mitigation), low direct mortality and almost undetectable indirect mortality post capture reinforces the efficacy of helicopter net-gunning for capture and recapture of mule deer in long-term, individual-based studies.     

Eagle visitation rates to carrion in a winter scavenging guild

Understanding the behavioral ecology of species of conservation concern can help to inform better management. During winters 2011 through 2017, we placed camera traps at stations baited with carrion to investigate characteristics of winter scavenging by golden eagles (Aquila chrysaetos) and bald eagles (Haliaeetus leucocephalus) in eastern Washington and Oregon, USA. Our objectives were to better understand exposure risk of individual eagles to lead contaminants and evaluate factors that affect eagle visitation to carrion to inform measures that reduce lead exposure. We studied photo sequences from 108 traps ( = 2,725 ± 306 [SE] images/trap) and used plumage and physical characteristics to track visitation of 183 individual golden eagles and 90 bald eagles at deer (Odocoileus spp.) carrion until it was totally consumed. At least 1 eagle visited 76% of traps ( = 2.5 ± 0.3 unique eagles/trap). On average, an eagle visited a trap 3.4 ± 0.2 times (range = 1–19 visits) over 1.9 ± 0.1 days (range = 1–9 days). We used general linear mixed models to identify influences on number of eagle visits and pooled visit duration. Individual golden eagles visited carrion about 25% more often and 50% longer than bald eagles, and individual juvenile eagles visited carrion more often and longer than immature and adult eagles. On average, an eagle made an additional visit to carrion for every golden eagle that came to the same trap. Eagles spent less time at offal ( = 26.2 ± 6.4 min) than at a whole carcass ( = 92.9 ± 7.5 min), and understory vegetation immediately surrounding carrion was associated with a 30% reduction in visitation time. In the Pacific Northwest during winter, adult and juvenile golden eagles, by virtue of their abundance and visitation to carrion compared to the immature age class and bald eagles of all ages, have the highest potential for exposure to anthropogenic effects from carrion visitation. Concealment of offal piles in vegetation may reduce, but not eliminate, eagle use because of competing scavengers that expose carrion locations. We found no evidence that carrion proximity to nearest known nests, topography, or snow cover affect visitation by eagles. Thus, short of using alternative ammunition to lead, we recommend burial or removal of offal from hunter-killed ungulates. © 2019 The Wildlife Society.     

Nest survival and productivity of translocated and resident burrowing owls in Arizona

Development activities associated with urbanization can directly displace animals, causing high mortality and dispersal rates. Wildlife managers have attempted to mitigate the impacts of development on burrowing owls (Athene cunicularia), a species susceptible to ground-disturbing activities, by translocating them away from areas slated for development. In this study, we evaluated the effects of translocation on burrowing owl reproduction by comparing nest survival and productivity of owls involved in an ongoing translocation program in Arizona, USA, with that of resident owls. We used nest survival models to evaluate differences in nest survival and generalized linear models with Poisson error to assess differences in productivity. In 2017, cumulative nest survival (CNS) was lower among current-year translocated owls (i.e., owls translocated within the last year; CNS = 0.34, 95% CI = 0.18, 0.51) compared to non-translocated resident owls (0.83, 95% CI = 0.71, 0.94), but CNS was similar between previously translocated owls (i.e., those translocated >1 yr ago, CNS = 0.81, 95% CI = 0.64, 0.98) and residents. Likewise, in 2018, CNS was lower for current-year translocated owls (CNS = 0.12, 95% CI = 0.00, 0.24) compared to residents (CNS = 0.68, 95% CI = 0.50, 0.87) and previously translocated owls (CNS = 0.65, 95% CI = 0.40, 0.90). Productivity was significantly lower for current-year translocated owls ($\bar{x}$ = 0.5 fledglings/nest) compared to residents ($\bar{x}$ = 2.4 fledglings/nest) and previously translocated owls ($\bar{x}$ = 1.5 fledglings/nest) across sites and years. With the current methods of translocation, owls had poor reproductive success in the first year after release, but if they survived 2 years after release, they had similar nest survival and productivity compared to residents. Our results demonstrate that the current practice of releasing translocated burrowing owls in the Phoenix, Arizona area during the breeding season depresses reproduction and should be substantially changed. Nest survival was low and this was mainly attributed to nest establishment of translocated owls within release tents (acclimation structures used in translocations that involve soft release) where 85% of nests failed following tent removal. Translocation approaches that reflect a closer fit to the timing and behavior of the species should be tested to determine whether they result in better success. In particular, future studies should examine the translocation results of releasing owls as male-female pairs or single birds during the nonbreeding period.     

Long-Term Spatiotemporal Dynamics and Factors Associated with Trends in Bare-Nosed Wombats

Geographically widespread species present challenges for conservation assessment. We used long-term spotlight surveys to assess spatiotemporal dynamics of bare-nosed wombats (Vombatus ursinus), encompassing 34 years of surveys for the Tasmanian mainland sub-species (V. u. tasmaniensis, 1985–2018) and 25 years for the Flinders Island sub-species (V. u. ursinus, 1994–2018). Wombat populations increased on the Tasmanian mainland by 2.59 times and on Flinders Island by 3.51 times ( = 1.05 and 1.1 times increase/yr, respectively). At smaller spatial scales on mainland Tasmania, increases in wombat counts generally occurred within meteorological regions and regional zones, except for the Central North (West Tamar) region where a decrease in wombats is linked to a sarcoptic mange disease epizootic. We used generalized additive models to assess relationships between variables and wombat counts. The most supported variables at the mainland Tasmania scale were (in order of importance) year, positive associations with time-lagged minimum temperature, Tasmanian devil (Sarcophilus harrisii) counts, and moonlight, and a negative association with time-lagged rainfall. Among meteorological regions, variables associated with wombat counts exhibited some heterogeneity, with temperature and rainfall the most frequently associated variables. Our long-term, large-scale, and ecologically diverse analysis of bare-nosed wombats supports spotlight monitoring as a valuable, relatively simple, and affordable survey method in Tasmania and beyond. © 2021 The Wildlife Society.     

Effects of Midazolam on Corticosterone and Blood Gases in Spectacled Eiders Prior to Transmitter Implantation

Stress and physical exertion may affect the physiology and behavior of wildlife during and after capture, and consequently, survival following release. Such effects may reduce the quality and quantity of the data obtained from captured wildlife. We captured spectacled eiders (Somateria fischeri), a species listed as threatened under the United States Endangered Species Act, in western Alaska, USA, during spring 2018 for surgical implantation of satellite transmitters. We evaluated the efficacy of midazolam, a benzodiazepine sedative given at capture, to reduce stress and physical exertion. We dosed spectacled eiders with either midazolam (5 mg/ml, = 2.2 mg/kg intramuscular; n = 20) or saline (0.7 ml intramuscular; n = 20) at the point of capture. We assessed sedation level and collected blood samples upon arrival to the field surgery site and at anesthetic induction. We found that midazolam reduced mean corticosterone concentration by 29% and median lactate concentration by 30.3% at the mean arrival time (42 min post-dosing) relative to the control group. These effects had abated by the mean induction time (99 min post-dosing). Unexpectedly, blood pH was reduced in the midazolam treatment relative to controls at both arrival and induction, which likely resulted from sedative-induced respiratory depression that was easily treated with intubation and mechanical ventilation, and administration of the reversal drug, flumazenil. Low blood pH was not associated with negative post-surgical outcomes, as had been found in spectacled eiders with acidosis caused by anaerobic metabolism typical of physical exertion. Intramuscular injection of midazolam in the field effectively reduced stress and physical exertion in spectacled eiders prior to surgical implantation of transmitters. © 2021 The Wildlife Society.     

Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

Predation is a major limiting factor for most small sedentary caribou (Rangifer tarandus) populations, particularly those that are threatened or endangered across the southern extent of the species’ range. Thus, reducing predation impacts is often a management goal for improving the status of small caribou populations, and lethal predator removal is the primary approach that has been applied. Given that predator control programs are often contentious, other management options that can garner broader public acceptance need to be considered. Substantial calf losses to predation in the few weeks following birth are common for these small caribou populations. Therefore, we employed a novel experimental approach of maternal penning with the goal of reducing early calf mortality in the Chisana Caribou Herd, a declining population in southwest Yukon and adjacent Alaska thought to number around 300 individuals. Maternal penning entailed temporarily holding pregnant females on their native range in a large pen secure from predators from late March through the initial weeks of calf rearing to mid-June. During 2003–2006, we conducted 4 annual penning trials with 17–50 pregnant females each year (n = 146 total), assessed survival of calves born in the pens, and evaluated survival and nutritional effects of penning for females that were held. We also investigated the herd's population dynamics during 2003–2008 to determine effects of maternal penning on calf recruitment and population growth. In addition to information gained during maternal penning, we determined natality and survival patterns via radiotelemetry, conducted autumn age-sex composition surveys each year, and censused the population in mid-October 2003, 2005, and 2007. Based on our penning trials and demographic investigations, we used simulation models to evaluate the effects of maternal penning relative to a population's inherent growth rate (finite rate of increase [λ] without maternal penning) and penning effort (proportion of calves born in penning) to provide perspective on utility of this approach for improving the status of small imperiled caribou populations. Pregnant females held in maternal penning tolerated captivity well in that they exhibited positive nutritional responses to ad libitum feed we provided and higher survival than free-ranging females (0.993 and 0.951 for penned and free-ranging females, respectively). Survival of pen calves from birth to mid-June was substantially higher than that of free-ranging calves ( = 0.950 and 0.376, respectively). This initial period accounted for 76% of the annual calf mortality in the free-ranging population. Pen-born calves maintained their survival advantage over wild-born calves to the end of their first year ( = 0.575 and 0.192, respectively) during years penning occurred. Females in the Chisana Herd were highly productive with 57% producing their first offspring at 2 years of age, and annual natality rates averaging 0.842 calves/female ≥2 years old. Age-specific natality rates exceeded 0.900 for 4–9-year-olds, then exhibited senescent decline to 0.467 by 19 years old. Annual survival of free-ranging adult females and calves averaged 0.892 and 0.184, respectively, over all study years; both were reduced during 2004 because of poor winter survival. We noted reduced nutritional condition of caribou late that winter in that females we captured were lighter than in other years and produced lighter calves. We suspect that the reduced survival during winter 2004 and the observed nutritional characteristics resulted from adverse snow conditions in combination with effects of the extreme drought experienced the previous summer. Age-specific survival of adult females was ≥0.900 through 10 years of age, then declined with age. The Chisana Herd numbered 720 caribou in mid-October 2003, or more than twice that estimated prior to initiating maternal penning, and increased to 766 caribou by mid-October 2007. We calculated that penning added 54.2 yearling recruits, or 40% of calves released from penning. Based on the maternal penning results and the population's vital rates, we determined that the herd would have been stable during 2003–2007 at about 713 caribou without maternal penning; thus, the increase in herd size we observed resulted from maternal penning and was equivalent to the estimate of additional yearling recruits. The improvement in the population trend invoked by maternal penning was limited by the larger than expected population size and resulting low penning effort ( = 11% of calves born in pen). Our simulations corroborated that maternal penning increased population size by the number of additional recruits provided, even at low penning effort, for inherently stable populations. As the inherent rate of increase dropped below λ = 1.000, more of the additional recruits from penning were needed to offset the downward population inertia, thus requiring increased penning effort to reach stability. For populations declining at λ < 0.890, stability could not be achieved with 100% penning effort given the vital rates in our models. Maternal penning in its limited application to date has proven to be broadly popular as a nonlethal management action aimed at reducing initial calf mortality from predation in small caribou populations. However, based on the Chisana program and 3 subsequent efforts elsewhere, improvement in population trends have been modest at best and come at a high financial cost. Given the necessity of maximizing penning effort, maternal penning may have a role in addressing conservation challenges for some small caribou populations that are stable or slowly declining, but its application should be primarily driven by objective assessment of the likelihood of improving population trends rather than popularity relative to other management options.     

Influence of Landscape Characteristics on Hunter Space Use and Success

Sport hunting of ungulates is a predominant recreational pursuit and the primary tool for managing their populations in North America and beyond, given its influence on ungulate distributions, social organization, and population performance. Similarly, land management, such as motorized vehicle access, influences ungulate distributions during and outside hunting seasons. Although research on ungulate responses to hunting and land use is widespread, knowledge gaps persist about space use of hunters and what landscape features discriminate among hunt types and between successful and unsuccessful hunters. We used telemetry location data from hunters (n = 341) to estimate space use from 2008–2013 during 3 types of controlled, 5-day hunts for antlered mule deer (Odocoileus hemionus) and elk (Cervus canadensis) in northeastern Oregon, USA: archery elk, rifle deer, and rifle elk. To evaluate space use, we developed utilization distributions for each hunter, created core areas (50% contours) for groups of hunters, and derived several metrics of space-use overlap between successful and unsuccessful hunters. We also modeled predictors of space use using resource utilization functions with beta regression and stepwise model building. Hunter space use was compressed, with even the largest core area (unsuccessful rifle elk hunters) encompassing <16% (1,178 ha) of the area. We found strong similarities in space use of rifle hunters compared to archers, and core areas of successful hunters were markedly smaller than those of unsuccessful hunters (e.g., = 104 ha vs. 681 ha, respectively, for archers). Percentage cover and distance from open roads were the most consistent covariates in the 6 final models (successful vs. unsuccessful for each of 3 hunts) but with different signs. For example, predicted use of archery and rifle elk hunters increased with cover but decreased for rifle deer hunters. Although the same covariates were in the final models for unsuccessful and successful rifle elk hunters, their negligible spatial overlap suggested they sought those features in different locales, a pattern also documented for rifle deer hunters. Our models performed well (Spearman's rank correlation coefficients = 0.99 for 5 of 6 models), reflecting their utility for managing hunters and landscapes. Our results suggest that strategic management of open roads and forest cover can benefit managers seeking to balance hunter opportunity and satisfaction with harvest objectives, especially for species of special concern such as mule deer, and that differences in space use among hunter groups should be accounted for in hunting season designs. © 2021 The Wildlife Society. This article has been contributed to by US Government employees and their work is in the public domain in the USA.     

Survival and fidelity of translocated and resident burrowing owls in Arizona

Given the rapid pace of urbanization, mitigation translocations are increasingly being used to reduce human-wildlife conflicts, especially to move animals out of the path of land development. Burrowing owls (Athene cunicularia) are commonly subjected to translocations because of their association with flat, open lands that are attractive to development. But outcomes of burrowing owl translocations and the effects they have on their demographic parameters are seldom documented. From 2017–2019, we tracked the fates of 42 resident (non-translocated) burrowing owls and 43 translocated owls using very high frequency radio-telemetry across 4 release sites in southcentral Arizona, USA. Translocations were conducted by Wild At Heart (WAH), a non-profit raptor rehabilitation program, and owls were moved from areas with planned development activities to release sites that contained artificial burrows. Each year, WAH held translocated owls in groups of 6–10 owls with varying male to female ratios in aviaries prior to taking the owls to release sites where the owls stayed in soft-release tents for an acclimation period of 30 days before release. Resident owls were located at or near the 4 release sites. We used the joint live encounter and dead recovery model to evaluate differences in survival and fidelity probabilities between resident (non-translocated) and translocated burrowing owls and to assess factors that influenced these probabilities including sex, year, site, captivity duration, and the number of males in release cohorts for translocated owls. Annual survival was consistently lower for translocated owls (0.35, 95% CI = 0.10, 0.61 and 0.01, 95% CI = 0.00, 0.03 for 2017 and 2018, respectively) compared to resident owls (0.68, 95% CI = 0.45, 0.92 and 0.69, 95% CI = 0.47, 0.90 for 2017 and 2018, respectively). Annual fidelity was lower for translocated owls (0.05, 95% CI = 0.00, 0.15) compared to resident owls (0.79, 95% CI = 0.57, 1.00) in 2018, but fidelity did not differ significantly between translocated (0.54, 95% CI = 0.19, 0.89) and resident owls (0.62, 95% CI = 0.37, 0.87) in 2017. For translocated owls, the number of males in release cohorts negatively affected survival ($\hat{\mathrm{\beta }}$ = −0.74, 95% CI = −1.07, −0.40) and fidelity ($\hat{\mathrm{\beta }}$ = −0.73, 95% CI = −1.17, −0.29). Our results indicate the need for substantial changes to the current translocation methodology for burrowing owls in Arizona. Breeding season releases that included owl groups and multiple males within cohorts resulted in agonistic interactions, high mortality, and low fidelity. Translocations of this territorial species should be restricted to male-female pairs or single individuals. Earlier releases may allow owls time to become established on release sites prior to the breeding season, which could promote fidelity. We recommend these changes be implemented and evaluated along with an examination of other release methods.     

Landscape Genetics of American Beaver in Coastal Oregon

American beaver (Castor canadensis) have been translocated for population restoration, reduction of human-wildlife conflict, and enhancement of ecosystem function. Yet few studies have assessed dispersal of beaver, making it difficult to determine at what scale translocations are appropriate. Genetic studies can provide inferences about gene flow, and thus dispersal. We used a landscape genetic approach to evaluate whether landscape features influenced gene flow among beaver in the Coast Range of western Oregon, USA, using samples collected April–September 2014. We collected genetic samples from live-captured (n = 232), road-killed (n = 2) and trapper-provided (n = 58) tissue samples and genotyped them at 10 microsatellite loci. We mapped records of beaver translocations into or within the study area during the twentieth century to consider the effect of those movements on genetic structure. We used population assignment tests to delimit genetic clusters, evaluated correspondence of those clusters with watershed boundaries and translocation history, and then estimated differentiation between clusters and between watersheds using model-based and model-free approaches. We evaluated how individual genetic differences varied with geographic distance, and investigated related pairs within clusters. We developed landscape resistance models incorporating slope, distance to water, and watershed boundaries at 2 scales, and estimated effective distances between sample locations with least cost path and circuit theoretic analyses. We evaluated the correlation of individual genetic distances with effective distances using a pseudo-bootstrapping approach. Landscape genetic models did not explain spatial variation in genetic structure better than geographic distance, but hierarchical genetic structure corresponded with watershed boundaries and suggested influences from historical translocations. Pairwise individual genetic distances were positively correlated with geographic distances to 61 km; highly-related pairs mostly were detected <1 km apart (median = 1.0 km, = 14.6 ± 2.3 [SE] km, n = 77). We concluded that slope and distance to water did not strongly limit dispersal and gene flow by beaver in this system, but concordance of genetic structure with watershed boundaries suggests that dispersal is more common within than between watersheds. Genetic differentiation of beaver within this topographically complex system was much greater than reported in a study at similar spatial scales in relatively flat topography. We recommend that translocation efforts of American beaver in topographically complex landscapes occur within watersheds when possible but conclude that dispersal can occur across watersheds. © 2021 The Wildlife Society. This article is a U.S. Government work and is in the public domain in the USA.     

Woodland caribou habitat selection patterns in relation to predation risk and forage abundance depend on reproductive state

The ideal free distribution assumes that animals select habitats that are beneficial to their fitness. When the needs of dependent offspring differ from those of the parent, ideal habitat selection patterns could vary with the presence or absence of offspring. We test whether habitat selection depends on reproductive state due to top‐down or bottom‐up influences on the fitness of woodland caribou (Rangifer tarandus caribou), a threatened, wide‐ranging herbivore. We combined established methods of fitting resource and step selection functions derived from locations of collared animals in Ontario with newer techniques, including identifying calf status from video collar footage and seasonal habitat selection analysis through latent selection difference functions. We found that females with calves avoided predation risk and proximity to roads more strongly than females without calves within their seasonal ranges. At the local scale, females with calves avoided predation more strongly than females without calves. Females with calves increased predation avoidance but not selection for food availability upon calving, whereas females without calves increased selection for food availability across the same season. These behavioral responses suggest that habitat selection by woodland caribou is influenced by reproductive state, such that females with calves at heel use habitat selection to offset the increased vulnerability of their offspring to predation risk.     

Influence of Juniper on Montezuma Quail Habitat Use in Texas

Montezuma quail (Cyrtonyx montezumae) inhabit oak (Quercus spp.)-juniper (Juniperus spp.) woodlands throughout Mexico and the southwestern United States. In Texas, USA, Montezuma quail occur in the Edwards Plateau and Trans-Pecos Mountains and Basins (Trans-Pecos), 2 ecoregions with contrasting juniper patterns. Ashe juniper (Juniperus ashei) dominates in the Edwards Plateau and has been increasing over decades, whereas alligator juniper (Juniperus deppeana) is a co-dominant in the Trans-Pecos and appears to have stable Montezuma quail populations. Our objectives were to compare between ecoregions the relative abundance and habitat use of Montezuma quail in relation to juniper and quantify the influence of juniper on key features of Montezuma quail habitat (grass height, grass cover, forb cover, and forb species richness). We conducted a study from March–August 2018‒2020 in the Edwards Plateau (Kinney and Edwards counties) and Trans-Pecos ecoregions (Jeff Davis County) to evaluate these objectives. We conducted call-back surveys to estimate relative abundance (number of detections/hr) of Montezuma quail and identify used locations. We collected vegetation data at a micro-scale (16-m) at used (n = 32–30 points) and random locations (n = 70–60 points) in each ecoregion. Relative abundance of Montezuma quail was considerably lower in the Edwards Plateau (0.06 ± 0.01 detections/survey hr; ± SE) than in the Trans-Pecos (1.10 ± 0.30 detections/survey hr). In addition, Montezuma quail selected areas of low Ashe juniper cover (<23% cover), density (<7 trees/80 m²), and height (<2 m) in the Edwards Plateau but selected areas of high alligator juniper cover (>18% cover), density (>4 trees/80 m²), and height (2–8 m) in the Trans-Pecos. Moreover, Ashe juniper cover had a significant, negative influence on herbaceous features, whereas alligator juniper exerted little to no influence. Our results suggest that these 2 juniper species have contrasting effects on Montezuma quail space use and their habitat, possibly as a result of the contrasting influence of these junipers on herbaceous understory. Creating habitat for Montezuma quail in the Edwards Plateau generally will involve the reduction of Ashe juniper and creating patches that possess juniper trees of small stature (<2 m) with low amounts of cover (<23%) and density (<7 trees/80 m²), whereas management in the Trans-Pecos will require site-specific assessments based on current alligator juniper influence. © 2021 The Wildlife Society.