Recolonizing wolves and mesopredator suppression of coyotes:impacts on pronghorn population dynamics

Food web theory predicts that the loss of large carnivores may contribute toelevated predation rates and, hence, declining prey populations, through the process ofmesopredator release. However, opportunities to test predictions of the mesopredator releasehypothesis are rare, and the extent to which changes in predation rates influence preypopulation dynamics may not be clear due to a lack of demographic information on the preypopulation of interest. We utilized spatial and seasonal heterogeneity in wolf distribution andabundance to evaluate whether mesopredator release of coyotes (Canis latrans), resulting fromthe extirpation of wolves (Canis lupus) throughout much of the United States, contributes tohigh rates of neonatal mortality in ungulates. To test this hypothesis, we contrasted causes ofmortality and survival rates of pronghorn (Antilocapra americana) neonates captured at wolf-free and wolf-abundant sites in western Wyoming, USA, between 2002 and 2004. We thenused these data to parameterize stochastic population models to heuristically assess the impactof wolves on pronghorn population dynamics due to changes in neonatal survival. Coyotepredation was the primary cause of mortality at all sites, but mortality due to coyotes was 34%lower in areas utilized by wolves (P , 0.001). Based on simulation modeling, the realizedpopulation growth rate was 0.92 based on fawn survival in the absence of wolves, and 1.06 atsites utilized by wolves. Thus, wolf restoration is predicted to shift the trajectory of thepronghorn population from a declining to an increasing trend. Our results suggest thatreintroductions of large carnivores may influence biodiversity through effects on preypopulations mediated by mesopredator suppression. In addition, our approach, whichcombines empirical data on the population of interest with information from other datasources, demonstrates the utility of using simulation modeling to more fully evaluateecological theories by moving beyond estimating changes in vital rates to analyses ofpopulation-level impacts

Use of Subsistence-Harvested Whale Carcasses by Polar Bears in the Southern Beaufort Sea

The availability of a food subsidy has the potential to influence the condition, behavior, fitness, and population dynamics of a species. Since the early 2000s, monitoring efforts along the coast of northern Alaska have indicated a higher proportion of polar bears (Ursus maritimus) of the southern Beaufort Sea (SB) subpopulation coming onshore to feed on subsistence-harvested bowhead whale (Balaena mysticetus) carcasses during the fall and early winter seasons. Concurrently, Indigenous communities annually hunt bowhead whale and deposit the unused remains at localized “bone piles,” creating the potential for human-bear interactions. Our objective was to determine the annual number of polar bears feeding at the bone pile near Kaktovik, Alaska. Using a hair snag surrounding the bone pile, we collected hair samples to identify individual bears via microsatellite genotypes during 2011 – 14. We used capture-mark-recapture data in the POPAN open-population model to estimate the number of bears visiting the bone pile. We estimated that as many as 72 (SE = 9) and 76 (SE = 10) male and female polar bears, respectively, used the bone pile located at Kaktovik, Alaska, in 2012, which represents approximately 16% of the SB polar bear subpopulation. It will be important to monitor the number of bears using the bone pile and subsequent human-bear interactions and conflicts along the northern coast of Alaska, if sea ice continues to recede.L’existence de subventions alimentaires a la possibilité d’influencer l’état, le comportement, la condition physique et la dynamique de la population d’une espèce. Depuis le début des années 2000, les efforts de surveillance déployés sur la côte nord de l’Alaska ont laissé entrevoir une plus grande proportion d’ours polaires (Ursus maritimus) de la sous-population du sud de la mer de Beaufort venant sur le littoral pour manger les carcasses des baleines boréales (Balaena mysticetus) pêchées à des fins de subsistance pendant les saisons de l’automne et du début de l’hiver. En même temps, les collectivités autochtones chassent les baleines boréales tous les ans et déposent leurs restes dans des « tas d’ossements », ce qui crée la possibilité d’interactions entre les humains et les ours. Notre objectif consistait à déterminer le nombre annuel d’ours polaires qui s’alimentent au tas d’ossements situé près de Kaktovik, en Alaska. De 2011 à 2014, à l’aide d’un piège à poils placé près du tas d’ossements, nous avons recueilli des échantillons de poils afin d’identifier les ours individuels au moyen de génotypes microsatellites. Nous avons employé les données de capture-marquage-recapture du modèle de population ouverte POPAN pour estimer le nombre d’ours se rendant au tas d’ossements. Nous avons estimé que jusqu’à 72 (ET = 9) et 76 (ET = 10) ours polaires mâles et femelles, respectivement, ont utilisé le tas d’ossements de Kaktovik, en Alaska, en 2012, ce qui représente environ 16 % de la sous-population d’ours polaires du sud de la mer de Beaufort. Il sera important de surveiller le nombre d’ours qui utilisent le tas d’ossements de même que les interactions et les conflits entre les humains et les ours qui s’ensuivront sur la côte nord de l’Alaska si la glace de mer continue de reculer

A meta-BACI approach forevaluating management intervention on chronic wasting disease in mule deer

Advances in acquiring and analyzing the spatial attributes of data have greatlyenhanced the potential utility of wildlife disease surveillance data for addressing problems ofecological or economic importance. We present an approach for using wildlife diseasesurveillance data to identify areas for (or of ) intervention, to spatially delineate pairedtreatment and control areas, and then to analyze these nonrandomly selected sites in a meta-analysis framework via before–after–control–impact (BACI) estimates of effect size. We applythese methods to evaluate the effectiveness of attempts to reduce chronic wasting disease(CWD) prevalence through intensive localized culling of mule deer (Odocoileus hemionus)innorth-central Colorado, USA. Areas where surveillance data revealed high prevalence or caseclusters were targeted by state wildlife management agency personnel for focal scale (onaverage ,17 km2) culling, primarily via agency sharpshooters. Each area of sustained cullingthat we could also identify as unique by cluster analysis was considered a potential treatmentarea. Treatment areas, along with spatially paired control areas that we constructed post hocin a case-control design (collectively called ‘‘management evaluation sites’’), were thendelineated using home range estimators. Using meta-BACI analysis of CWD prevalence datafor all management evaluation sites, the mean effect size (change of prevalence on treatmentareas minus change in prevalence on their paired control areas) was 0.03 (SE ¼ 0.03); meaneffect size on treatment areas was not greater than on paired control areas. Excluding cullsamples from prevalence estimates or allowing for an equal or greater two-year lag in systemresponses to management did not change this outcome. We concluded that managementbenefits were not evident, although whether this represented true ineffectiveness or was a resultof lack of data or insufficient duration of treatment could not be discerned. Based on ourobservations, we offer recommendations for designing a management experiment with 80%power to detect a 0.10 drop in prevalence over a 6–12-year period

Survival of the Fattest: How Body Fat and Migration Influence Survival in Highly Seasonal Environments

1. Energy stores and migration are important adaptations for animals in seasonal environments, but their roles may vary relative to an animal\u27s endogenous and exogenous environment. In partially migratory populations, migrants and residents experience different seasonal environments; thus, the influence of energy stores on survival may differ relative to migratory tactic, with potential consequences to survival and fitness. 2. Using data from Sierra Nevada bighorn sheep (Ovis canadensis sierrae; hereafter, Sierra bighorn), we tested the hypothesis that body fat (energy stores) buffers animals against their environment, but that buffering capacity differs across environments experienced by high-elevation residents (using a single range year round), traditional migrants (making 1 round-trip movement between high- and low-elevation ranges during winter) and vacillating migrants (making ≥2 round trips between high- and low-elevation ranges during winter). We predicted that: for animals with high levels of body fat, survival would be high regardless of migratory tactic; residents would require larger stores of body fat to survive than migrants; energy stores would be least influential to survival for vacillating migrants. 3. High levels of body fat in autumn (≥14% for females and ≥19% for males) largely buffered animals against harsh environments (survival \u3e0.90) regardless of migratory tactic. At lower levels of body fat, traditional migrants had higher survival than residents. Vacillating migrants exhibited nearly 100% survival with no detectable effect of body fat on survival. 4. Collectively, these results support the hypothesis that body fat buffers animals against harsh environments but that the buffering capacity differed relative to the environment and highly flexible behaviours (i.e. vacillating migration) can allow animals to decouple survival from body fat. 5. Our work reveals that synergies between physiological and behavioural adaptations of animals in highly seasonal environments carry potential fitness consequences for individuals and demographic consequences for populations

Targeting alphas can make coyote control more effective and socially acceptable

Research at the UC Hopland Research and Extension Center (HREC) has improved our understanding of how to reduce sheep depredation while minimizing the impact on coyotes. Analysis of a 14-year data set of HREC coyote-control efforts found that sheep depredation losses were not correlated with the number of coyotes removed in any of three time scales analyzed (yearly, seasonally and monthly) during corresponding intervals for the next 2 years. Field research using radiotelemetry to track coyotes supported and explained this finding. For example, in 1995, dominant “alphas” from four territories were associated with 89% of 74 coyote-killed lambs; “betas” and transients were not associated with any of these kills. Relatively few coyotes were killing sheep, and these animals were difficult to capture by conventional methods at the time of year when depredation was highest. However, selective removal of only the problem alpha coyotes effectively reduced losses at HREC

Targeting alphas can make coyote control more effective and socially acceptable

Research at the UC Hopland Research and Extension Center (HREC) has improved our understanding of how to reduce sheep depredation while minimizing the impact on coyotes. Analysis of a 14-year data set of HREC coyote-control efforts found that sheep depredation losses were not correlated with the number of coyotes removed in any of three time scales analyzed (yearly, seasonally and monthly) during corresponding intervals for the next 2 years. Field research using radiotelemetry to track coyotes supported and explained this finding. For example, in 1995, dominant “alphas” from four territories were associated with 89% of 74 coyote-killed lambs; “betas” and transients were not associated with any of these kills. Relatively few coyotes were killing sheep, and these animals were difficult to capture by conventional methods at the time of year when depredation was highest. However, selective removal of only the problem alpha coyotes effectively reduced losses at HREC

Best management practices in counting urban black bears

DNA-based capture-mark-recapture (CMR) techniques are commonly used to obtain population parameters of black bears (Ursus americanus) in rural and wildland landscapes; however, these techniques have not been implemented in urban clusters (i.e., 2,500 to 50,000 residents). Black bears can readily habituate to urban clusters, and wildlife managers need to monitor and manage these urban bear populations. We modified DNAbased CMR for black bear using hair-snares to take into account the small home ranges of urban bears, urban bear behavior, and human safety within Mammoth Lakes, California, USA. We conducted this study for 3 fi eld seasons in 2010, 2011, and 2012 from June to July. Each fi eld season, we implemented a CMR with 6 encounter occasions, each 7 days in length. We used the traditional corral hair-snare design modified for human safety and chose multiple non-consumable and minimally consumable lure types to prevent food conditioning and a trap-happy response. In 2012, we also tested 3 additional hair-snare designs more appropriate for urban areas: natural rub, haphazard-wire snare, and tennis ball snare. In 2010, we collected an insufficient number of hair samples for CMR by putting hair-snares in the periphery of the urban cluster, which we call the urban–wildland interface. However, in 2011 and 2012, when we put hair-snares in the city center as well as the surrounding urban–wildlife interface and increased hair-snare density, we obtained a sufficient number of hair samples to estimate population density using closed capture CMR models. These adjustments to hairsnaring study design in urban areas helped increase capture and recapture rates to be similar to our wildland area. To achieve high capture rates using hair-snares in the urban area, we put out hair-snares at a density approximately 4 times greater than in our wildland study area and distributed them throughout the entire urban area, and not just on the urban–wildlife interface. In addition, setting hair-snares near anthropogenic features used by bears in urban areas (e.g., culverts, utility poles, dumpsters) and adding spent cooking oil to lures also increased our capture rate. Finally, the corral hair-snare had the highest capture rates of our 4 hair-snare designs. After adapting a study design for hair-snaring wildland bears, our methods were efficient for urban areas, having high capture and recapture rates (\u3e0.30) and good precision for abundance estimates (coefficient of variatio