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At least 1,729 records · Page 96Linked to original sources
USGS2016

Proximate influences on female dispersal in white-tailed deer

Ultimate causes of animal dispersal have been hypothesized to benefit the dispersing individual because dispersal reduces competition for local resources, potential for inbreeding, and competition for breeding partners. However, proximate cues influence important features of dispersal behavior, including when dispersal occurs, how long it lasts, and direction, straightness, and distance of the dispersal path. Therefore, proximate cues that affect dispersal influence ecological processes (e.g., population dynamics, disease transmission, gene flow). We captured and radio-marked 277 juvenile female white-tailed deer ( Odocoileus virginianus ), of which 27 dispersed, to evaluate dispersal behavior and to determine proximate cues that may influence dispersal behavior. Female dispersal largely occurred at 1 year of age and coincided with the fawning season. Dispersal paths varied but generally were non-linear and prolonged. Physical landscape features (i.e., roadways, rivers, residential areas) influenced dispersal path direction and where dispersal terminated. Additionally, forays outside of the natal range that did not result in dispersal occurred among 52% of global positioning system (GPS)-collared deer ( n = 25) during the dispersal period. Our results suggest intra-specific social interactions and physical landscape features influence dispersal behavior in female deer. Female dispersal behavior, particularly the lack of directionality, the semi-permeable nature of physical barriers, and the frequency of forays outside of the natal range, should be considered in regard to population management and controlling the spread of disease.

Pennsylvania↗
USGS2011

Using multilevel models to quantify heterogeneity in resource selection

Models of resource selection are being used increasingly to predict or model the effects of management actions rather than simply quantifying habitat selection. Multilevel, or hierarchical, models are an increasingly popular method to analyze animal resource selection because they impose a relatively weak stochastic constraint to model heterogeneity in habitat use and also account for unequal sample sizes among individuals. However, few studies have used multilevel models to model coefficients as a function of predictors that may influence habitat use at different scales or quantify differences in resource selection among groups. We used an example with white-tailed deer ( Odocoileus virginianus ) to illustrate how to model resource use as a function of distance to road that varies among deer by road density at the home range scale. We found that deer avoidance of roads decreased as road density increased. Also, we used multilevel models with sika deer ( Cervus nippon ) and white-tailed deer to examine whether resource selection differed between species. We failed to detect differences in resource use between these two species and showed how information-theoretic and graphical measures can be used to assess how resource use may have differed. Multilevel models can improve our understanding of how resource selection varies among individuals and provides an objective, quantifiable approach to assess differences or changes in resource selection.

Journal of Wildlife Management↗
USGS2016

Oil and gas development influences big-game hunting in Wyoming

Development from extracting oil and gas resources can have unintended effects on multiple ecosystem functions, with cascading effects on wildlife, ecosystem services, and local economies. Big-game hunting opportunities may be closely related to these effects, but empirical analyses of impacts of energy development on hunting are limited. We examined the influence of oil and gas development density on harvest efficiency, or harvest per unit of hunter effort, within all hunt areas in Wyoming, USA, from 2008 to 2014 for 3 big-game species: elk ( Cervus canadensis ), mule deer ( Odocoileus hemionus ), and pronghorn ( Antilocapra americana ). Using harvest/hunter day as the response variable, we compared linear mixed-effects models for each species that included total well density (i.e., all wells constructed up to the year of record), active well density (i.e., only those wells currently producing oil or gas in that year), or neither as a predictor variable. We used well densities as indicators of development in the absence of data specifying the locations of other oil and gas infrastructure (e.g., roads, well pads). Models also accounted for the fixed effects of road density, hunter density, proportion of the area that is public land with unrestricted hunter access, proportion of the area that is forested, year of observation, and random effects of variation among hunt areas nested within associated game herd units. Presence of oil and gas wells had a positive influence on harvest efficiency for elk and mule deer. Although there was no overall effect to pronghorn, there was a negative influence of wells on juvenile pronghorn harvest efficiency. Changes in harvest efficiency due to expanding oil and gas development could alter the time spent hunting by hunters and their chances of harvesting an animal. This could have subsequent impacts on hunter satisfaction, game populations, and economic revenue generated from recreational hunters.

Wyoming↗
USGS2018

Response of moose to a high‐density road network

Road networks and the disturbance associated with vehicle traffic alter animal behavior, movements, and habitat selection. The response of moose ( Alces americanus ) to roads has been documented in relatively rural areas, but less is known about moose response to roads in more highly roaded landscapes. We examined road‐crossing frequencies and habitat use of global positioning system (GPS)‐collared moose in Massachusetts, USA, where moose home ranges have road densities approximately twice that of previous studies. We compared seasonal road‐crossing frequencies of moose with a null movement model. We estimated moose travel speeds during road‐crossing events and compared them with speeds during other home range movements. To estimate the extent of the road effect zone and determine how roads influenced moose habitat use, we fit a third‐order resource selection function. With the exception of the lowest use road class (<10 vehicles/day), we found moose crossed roads less than expected based on the null movement model and frequency decreased with increasing road size and traffic. Moose crossed roads faster than they traveled during other times. This effect increased with increasing road use intensity. Overall, roads were a major factor determining what portions of Massachusetts moose used and how they moved among habitat patches. Our results suggest that moose in Massachusetts can adapt to a high‐density road network, but the road effect is still strongly negative and, in some cases, is more pronounced than in study areas with lower road densities. Future road construction and the expansion of road networks may have a large effect on moose and other wildlife.

Journal of Wildlife Management↗
USGS2018

Modeling golden eagle‐vehicle collisions to design mitigation strategies

The incidental take of golden eagles ( Aquila chrysaetos ) as a result of wind energy development requires some form of compensatory mitigation. Although several options have been proposed, only one has been formerly accepted and implemented, and the lack of options can limit the permit process for wind facilities. We developed a model to estimate numbers of golden eagles that die when struck by vehicles when eagles scavenge road kill to evaluate removal of road‐killed carcasses as an additional mitigation option. Our model estimates vehicle collision rates as a function of eagle densities, road traffic volume, and animal carcass abundance at the scale of a Wyoming, USA, county during fall‐winter, and quantifies the effects of different mitigation strategies, including estimates of uncertainty. We evaluated the plausibility of our model estimates by predicting mortality rates for each county in Wyoming and comparing overall state mortality to current estimates of mortality using derived estimates from expert judgment. We also developed a context‐dependent analysis of potential mitigation credits controlling for carcass number, traffic volume, and background carcass removals. We found that mitigation credit should be highest in areas with greatest number of carcasses. Collision mitigation is a potentially useful addition to the mitigation toolbox for wind energy development or other activities that need to offset predicted golden eagle mortality and satisfy incidental take permit requirements.

Wyoming↗
USGS2018

Effects of prescribed fire on San Francisco gartersnake survival and movement

The application of fire is prescribed for management of habitats for many plant and animal communities, but its effects on herpetofauna are diverse and remain poorly understood. To date no studies have examined the effects of prescribed fire on endangered San Francisco gartersnake ( Thamnophis sirtalis tetrataenia ) populations, despite a call for prescribed fire in the recovery plan for the species. We used multi‐state capture‐mark‐recapture models to assess whether effects of prescribed fire were ephemeral, occurring only during the year of the fire, or persisted for 3 years following the fire, and to estimate the effects of prescribed fire on demographic parameters of San Francisco gartersnakes inhabiting California coastal prairie. Ephemeral fire effects were better supported for transitions (movement) between burned and unburned areas, but persistent fire effects were better supported for apparent survival and recapture probabilities. Movement between burned and unburned areas decreased during the year of the fire, but transition rates from burned to unburned areas decreased less than transition rates from unburned to burned areas in the year of the fire. Apparent survival probabilities increased in the unburned areas following the fire but were largely unchanged, though more uncertain, in burned areas following the fire. Recapture probabilities decreased site‐wide following the fire, though the decrease was greater in burned areas than in unburned areas. Although imprecise, our estimates of the effects of prescribed fire suggest that under the conditions of this fire (low‐intensity fall burn applied to a small area within a robust population and followed by wet weather), prescribed fire is a viable management tool for maintaining open habitats where San Francisco gartersnakes occur.

California↗
USGS2019

Trends and carrying capacity of sea otters in Southeast Alaska

Sea otter populations in Southeast Alaska (SEAK) have increased dramatically from fewer than 500 translocated animals in the late 1960s. The recovery of sea otters to ecosystems from which they had been absent has affected coastal food webs, including commercially important fisheries, and thus information on expected growth and equilibrium abundances can help inform resource management. We compile available survey data for SEAK and fit a Bayesian state-space model to estimate past trends and current abundance. Our model improves upon previous analyses by partitioning and quantifying sources of estimation error, accounting for over-dispersion of aerial count data, and providing realistic measurements of uncertainty around point estimates of abundance at multiple spatial scales. We also provide the first estimates of carrying capacity (K) for SEAK, at both regional and sub-regional scales, and analyze growth rates, current population status and expected future trends. At the regional scale, the population increased from 13,221 otters in 2003 (95% credible interval 9,990 – 16,828) to 25,584 otters in 2011 (CI95 18,739 – 33,163). The average annual growth rate in southern SEAK (7.8%) was higher than northern SEAK (2.7%); however, growth varied at the sub-regional scale and there was a negative relationship between growth rates and the number of years sea otters were present in an area. Local populations vary in terms of current densities and expected future growth: the mean estimated density at K was 4.2 (1.58) sea otters per km2 of habitat (defined as the sub-tidal benthos between 0-40m depth) and current densities correspond on average to 50% of projected equilibrium values (range = 1% to 97%) with the earliest-colonized sub-regions tending to be closer to K. Assuming a similar range of equilibrium densities for currently un-occupied habitats in SEAK, the projected value of K for all of SEAK is 74,650 sea otters (CI95 =36,778–136,506). Future analyses can improve upon the precision of K estimates by employing more frequent surveys at index sites and incorporating environmental covariates into the process model to generate habitat-specific estimates of equilibrium density.

Alaska↗
USGS2019

Survival and movements of head‐started Mojave desert tortoises

Head‐starting is a conservation strategy in which young animals are protected in captivity temporarily before their release into the wild at a larger size, when their survival is presumably increased. The Mojave desert tortoise ( Gopherus agassizii ) is in decline, and head‐starting has been identified as one of several conservation measures to assist in recovery. To evaluate the efficacy of indoor head‐starting, we released and radio‐tracked 68 juvenile tortoises from a 2015 cohort in the Mojave National Preserve, California, USA. We released 20 tortoises at hatching (control) in September 2015, and reared 28 indoors and 20 outdoors in predator‐proof enclosures for 7 months before releasing them in April 2016. We monitored tortoises at least weekly after release until 27 October 2016, and documented survivorship, movement, and surface activity. We estimated survivorship by treatment and evaluated effects of treatment, proximity to a raven ( Corvus corax ) nest (predator) coincidentally established after release, distance moved between monitoring events, surface activity, and release size on individual fate in a generalized linear model. Although indoor head‐start tortoises reached the size of 5–6‐year‐old wild tortoises by release at 7 months of age, survival did not differ significantly among the 3 treatment groups. Combined annual survival was 0.44 (95% CI = 0.34–0.58). Tortoises that were closer to an active raven nest were significantly more likely to die, as were those seen more often outside their burrows and active aboveground. Predicted estimates for short‐term probability of survival approached 1.0 as distance from a raven nest exceeded approximately 1.6 km. Rearing treatment, movement distance, and body size were not significant predictors of fate over the 1‐year monitoring period. Head‐started tortoises released ≥1.6 km from areas of raven activity will likely have higher short‐term survival. Population recovery through head‐starting alone is unlikely to be successful if systemic ecosystem‐level issues, such as habitat degradation and conditions that promote human‐subsidized predators, are not ameliorated. © 2019 The Wildlife Society.

California↗
USGS2019

Caribou use of habitat near energy development in Arctic Alaska

Increasing demands for energy have generated interest in expanding oil and gas production on the North Slope of Alaska, raising questions about the resilience of barren-ground caribou populations to new development. Although the amount of habitat lost directly to energy development in the Arctic will likely be relatively small, there are significant concerns about habitat that may be indirectly impacted due to caribou avoidance behaviors. Behavioral responses to energy development for wildlife have been well-documented, but such responses are often assumed to dissipate over time, despite scant information on the ability of animals to habituate. To understand the long-term effects of energy development on barren-ground caribou we investigated the behavior of the Central Arctic Herd in northern Alaska, which has been exposed to oil development on its summer range for approximately 40 years. Using recent (2015-2017) location data from GPS collared females, we conducted a zone of influence analysis to assess whether caribou reduced their use of habitat near energy development, and if so, the distance the effects attenuated. We conducted this analysis for the calving, post-calving and mosquito harassment periods when caribou exhibit distinct resource selection patterns, and contrasted our results to past research that investigated the responses of the Central Arctic Caribou Herd immediately following the construction of the oil fields. Despite the long-term presence of energy development within the Central Arctic Herd summer range, we found that female caribou exhibited avoidance responses to infrastructure during all time periods, although the effects waned across the summer. Caribou reduced their use of habitat within 5 km of development during the calving period, within 2 km during the post-calving period, and within 1 km during the mosquito harassment period, areas which were predicted to overlap 12%, 15% and 17% of important calving, post-calving, and mosquito habitat areas, respectively. During the calving period, the indirect effects we observed were similar to those observed in past research, whereas during the post-calving and mosquito periods, we detected avoidance responses which had not been previously reported. These findings corroborate a growing body of evidence suggesting that habituation to industrial development in Arctic caribou is likely to be weak or absent, and emphasizes the value of minimizing the footprint of infrastructure within important seasonal habitat areas to reduce behavioral impacts to barren-ground caribou.

Alaska↗
USGS2020

Transmitter effects on growth and survival of Forster’s tern chicks

Radio‐telemetry is a commonly used scientific technique that allows researchers to collect detailed movement, habitat use, and survival data of animals; however, evidence indicates that using telemetry can affect behavior and survival. Using multiple breeding colonies and years, we investigated the effects of attached radio‐transmitters on growth and survival of Forster's tern ( Sterna forsteri ) chicks in San Francisco Bay, California, USA, 2010–2011. We tested these potential effects at isolated islands that allowed for high re‐capture rates (typically >85%) in radio‐marked and banded‐only chicks. Modeled Gompertz growth curves suggested that transmitters had a small negative effect on some of the asymptotic growth parameters of tern chicks; tarsus (−1.5 ± 0.7% [SE]), culmen (−1.7 ± 1.2%), and wing (−4.9 ± 2.0%) lengths were shorter for radio‐marked chicks compared to banded‐only chicks. In contrast, there was no difference in asymptotic mass between radio‐marked chicks and banded‐only chicks. Survival from hatching to fledging was lower for radio‐marked chicks than banded‐only chicks during 2010 (banded‐only = 0.313 ± 0.162 vs. radio‐marked = 0.250 ± 0.165) and 2011 (0.193 ± 0.030 vs. 0.123 ± 0.027). Most of the transmitter effect occurred within the first week after hatching, rather than in older chicks. Notably, the effect of transmitters on chick survival was primarily additive, indicating that the effect of transmitters on radio‐marked chicks was not influenced by other ecological covariates. Given the effect radio‐transmitters had on survival did not change across temporal or ecological gradients, transmitters can still be used to evaluate ecological factors affecting survival and timing of mortality and radio‐marked birds can be used to make inferences to the general population.

California↗
USGS2020

Black bear movement and food conditioning in an exurban landscape

Conflicts between humans and wildlife have become increasingly important challenges for resource managers along the urban‐wildland interface. Food conditioning (i.e., reliance by an animal on anthropogenic foods) of American black bears (Ursus americanus ) is related to conflict behavior (i.e., being bold or aggressive toward humans, consuming human food or garbage, causing property damage) and often occurs in communities adjacent to Great Smoky Mountains National Park (GRSM or Park), USA. The goal of our study was to evaluate black bear space use in GRSM and in exurban areas on surrounding private lands and to identify factors associated with food conditioning and conflict behavior. We radio‐collared 53 bears (29 males, 24 females) from 2015 to 2017 to compare space use characteristics and used carbon isotopic signatures (δ13C) from bear hair to assess food conditioning. We then performed an integrated step selection function (iSSF) analysis to characterize and compare movement and resource use as related to food conditioning. Based on the stable isotope analyses, 24 bears were classified as food conditioned (FC; 16 males and 8 females) and 37 were not food conditioned (NFC; 14 males and 23 females). Annual 95% kernel density estimate (KDE) home ranges and 50% KDE core area estimates of female and male bears did not differ by level of food conditioning (i.e., mean δ13C), but 95% and 50% home ranges of FC females were smaller than NFC females when data from 2015, a year of food scarcity and abnormally large home ranges, were excluded. The mean proportion of exurban development (e.g., roads, buildings, openings) within 95% KDE and 50% KDE home ranges of females increased with mean δ13C (i.e., greater food conditioning). The iSSF models indicated that FC bears were more likely to use forest openings associated with higher levels of development than NFC bears. We used those models to demonstrate how landscape modifications can reduce bear use of exurban areas, particularly for NFC bears. Our stable isotope, movement, and resource use data indicate that conflict behaviors displayed by many bears within GRSM were learned in areas outside Park boundaries. © 2020 The Wildlife Society.

Tennessee, North Carolina↗
USGS2020

Use of upland and riparian areas by wintering bald eagles and implications for wind energy

Weather can shape movements of animals and alter their exposure to anthropogenic threats. Bald eagles ( Haliaeetus leucocephalus ) are increasingly at risk from collision with turbines used in onshore wind energy generation. In the midwestern United States, development of this energy source typically occurs in upland areas that bald eagles use only intermittently. Our objective was to determine the factors that cause wintering bald eagles to occupy riparian areas and riskier, upland areas. We tracked 20 bald eagles using telemetry in the Upper Midwest (MN, IA, MO, WI, IL, USA) during winter 2014–2015 and 2015–2016 and evaluated habitat use by eagles in response to variation in weather and time of year. Eagles used riparian areas more when wind speed and atmospheric pressure were low. Exclusive use of uplands was more frequent during weather systems with low pressure and high humidity and after long periods of cold weather. There was a non‐linear response to time of year (measured by days before migration) in the frequency of exclusive use of uplands or riparian areas. Probability of exclusive use of either landscape was generally constant within 95 days prior to migration. The probability of use of riparian areas, however, was markedly less during dates >100 days before migration. Our results suggest that eagles are most likely to be exposed to wind energy developments located in upland areas during low pressure systems, after long periods of cold weather, and several months before the onset of spring migration. This information helps to better understand the factors influencing bald eagle habitat use in winter and will be useful to managers and developers wishing to establish effective strategies to avoid, minimize, and mitigate take, and to survey for mortalities at wind energy developments.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗
USGS2021

Feral horse space use and genetic characteristics from fecal DNA

Feral horses ( Equus ferus caballus ) in the western United States are managed by the Bureau of Land Management (BLM) and United States Forest Service in designated areas on public lands with a goal of maintaining populations in balance with multiple uses of the landscape. Small, isolated populations can be at risk of extirpation from stochastic events and deleterious genetic effects resulting from inbreeding and reduced heterozygosity. The genetic diversity of feral horse herds is periodically monitored using blood or hair samples collected during management gathers (i.e., occasions when the herd is rounded up). We conducted a study to examine genetic characteristics of the feral horse population at the BLM Little Book Cliffs Herd Management Area (HMA) in Colorado, USA, using non-invasively collected fecal samples. Additionally, we explored whether genotypes could be used to document space use and potential sub-population development. We used a random sampling scheme, walking transects in sampling areas covering most of the HMA to find and collect fecal samples of all ages, except those that were deteriorating. We collected >1,800 fecal samples from across the study area in May, August, and October 2014. We then identified unique individuals using a suite of microsatellite loci. Our estimates of genetic diversity from fecal samples were higher than those reported from blood and hair samples taken during recent horse gathers, likely because our sample size and spatial distribution was larger. Genotypes revealed that some individuals were found only in certain parts of the study area and at a higher proportion than random; thus, they could be considered residents in those sampling areas. Using discriminant function analyses, we detected 5 genetic groups in the sample population, but these did not correspond to individuals in specific parts of the study area. Our results support the use of fecal DNA to augment direct observations of horse presence and could be used to detect habitat use and areas of high density. Non-invasive techniques such as fecal DNA sampling can help managers decide whether new individuals need to be translocated to a closed population to maintain genetic diversity without the human safety and animal welfare concerns associated with gathers and invasive techniques.

Colorado↗
USGS2020

Sex-specific behaviors of hunted mule deer during rifle season

Animal populations face increased threats to mobility and access to critical habitat from a variety of human disturbances including roads, residential development, agriculture, and energy development. Disturbance from human hunting is known to alter habitat use in ungulates, but recent work suggests that hunting may also trigger the onset of migration. Whether this holds true across ungulate species and hunting systems warrants further empirical testing. We used global positioning system location data from mule deer ( Odocoileus hemionus ) in south-central Wyoming, USA, to evaluate the sex-specific effects of hunting on habitat selection and migratory behavior from 2016 to 2018. We modeled habitat selection before and during hunting season using a step selection function, and we used time-to-event models to evaluate if hunting triggered migration. We found habitat selection and migration timing to be sex specific. Males responded to hunting season by selecting security habitat away from motorized routes, whereas females used habitat through hunting season that retained higher forage quality. Weather, as indexed by temperature and precipitation (i.e., snowfall), influenced migration timing for males and females. Migration timing in males was influenced by migration distance, where individuals traveling >50 km tended to migrate earlier than individuals moving <50 km. For deer that survived to rifle season, hunting was less influential on migration timing than environmental factors. Rifle season increased the likelihood of migration by 2% in females and <0.01% in males compared to outside rifle season. Our findings suggest that roadless areas on mule deer summer ranges and within migration corridors reduce the effects of hunting disturbance. Consequently, managers may consider limiting the use of motorized vehicles as a method for reducing effects on migration from hunting disturbance.

Colorado, Wyoming↗
USGS2021

Waif gopher tortoise survival and site fidelity following translocation

Gopher tortoises ( Gopherus polyphemus ) are among the most commonly translocated reptiles. Waif tortoises are animals frequently of unknown origin that have been displaced from the wild and often held in human possession for various reasons and durations. Although there are risks associated with any translocation, waif tortoises are generally excluded from translocation projects because of heightened concerns of introducing pathogens and uncertainty about the post-release survival of these individuals. If these risks could be managed, waif tortoises could have conservation value because they can provide the needed numbers to stabilize populations. In the early 1990s, the discovery of an isolated population of gopher tortoises (≤15 individuals) near Aiken, South Carolina, USA, prioritized establishment of the Aiken Gopher Tortoise Heritage Preserve (AGTHP). Because of the population's need for augmentation and the site's isolation from other tortoise populations, the AGTHP provided the opportunity to evaluate the post-release survival of translocated waif tortoises without compromising a viable population. Since 2006, >260 waif tortoises have been introduced to the preserve. Using a Cormack-Jolly-Seber modeling framework to analyze release records and capture histories from trapping efforts in 2017 and 2018, we estimated the long-term apparent survival and site fidelity of this population composed largely of waif tortoises. We estimated annual apparent survival probabilities to be high (≥0.90) for subadult, adult male, and adult female tortoises, and these rates were similar to those reported for wild-to-wild translocated gopher tortoises and those from unmanipulated populations. Of the tortoises recaptured within the boundaries of the preserve, 75% were located within 400 m of their release location. These results suggest that waif tortoises could be an important resource in reducing the extirpation risk of isolated populations. © 2021 The Wildlife Society.

South Carolina↗
USGS2021

Estimating abundance and simulating fertility control in feral burros

Overabundant populations of feral equids are negatively impacting rangelands in the western United States. To effectively manage these populations, robust estimates of abundance and demography are necessary, as well as cost-effective methods of reducing abundance. We used a double-observer-sightability aerial survey method to estimate the number of feral burros (Equus asinus) occupying the Fort Irwin National Training Center (NTC), California, USA. We examined the efficacy of using porcine zona pellucida (PZP) immunocontraception as a control agent and used matrix population models to simulate how changes in demographic rates would influence abundance. We estimated there were 690 (CI: 618–752) feral burros within the surveyed area, but these are part of a much larger population that is not geographically isolated from those in the survey area. Sighting probabilities ranged from 0.19–0.98 and were most strongly influenced by distance from observer and group size. We estimated age-specific demographic rates at the NTC and compiled mean rates across burro populations in arid environments from the literature. Mean fecundity varied from 0.17 to 0.58 foals per adult female with younger females having lower fecundity. Mean survival was 0.90 for foals, 0.98 for yearlings, and 0.96 for adults. PZP vaccine treatment strategies that suppressed fertility for up to 10 years, predicted that burro abundance would be reduced by 67–88% after 15 years (compared with no treatment), but none of these strategies resulted in population extirpation. Our fieldwork also highlights the difficulty of administering PZP vaccination to large, free-ranging animals. Burro growth rates shifted from increasing to decreasing at adult survival rates below 0.84 and the population was predicted to become extirpated when adult survival declined below 0.60. In the absence of other methods to reduce burro numbers, our findings indicate that current formulations of PZP immunocontraception, which require multiple doses, would be inadequate for controlling population growth rates at the NTC and perhaps elsewhere. Development of longer-term fertility reduction agents and/or more efficient vaccine delivery techniques would likely improve the efficacy of fertility control for overabundant ungulate populations. Lack of geographic closure (physical barriers to migration) further complicates management efforts to reduce burro numbers.

California↗
USGS2021

Sage-grouse population dynamics are adversely impacted by overabundant feral horses

In recent decades, feral horse ( Equus caballus ; horse) populations increased in sagebrush ( Artimesia spp.) ecosystems, especially within the Great Basin, to the point of exceeding maximum appropriate management levels (AML max ), which were set by land administrators to balance resource use by feral horses, livestock, and wildlife. Concomitantly, greater sage-grouse ( Centrocercus urophasianus ; sage-grouse) are sagebrush obligates that have experienced population declines within these same arid environments as a result of steady and continued loss of seasonal habitats. Although a strong body of research indicates that overabundant populations of horses degrade sagebrush ecosystems, empirical evidence linking horse abundance to sage-grouse population dynamics is missing. Within a Bayesian framework, we employed state-space models to estimate population rate of change ( λ ) using 15 years (2005–2019) of count surveys of male sage-grouse at traditional breeding grounds (i.e., leks) as a function of horse abundance relative to AML max and other environmental covariates (e.g., wildfire, precipitation, % sagebrush cover). Additionally, we employed a post hoc impact-control design to validate existing AML max values as related to sage-grouse population responses, and to help control for environmental stochasticity and broad-scale oscillations in sage-grouse abundance. On average, for every 50% increase in horse abundance over AML max , our model predicted an annual decline in sage-grouse abundance by 2.6%. Horse abundance at or below AML max coincided with sage-grouse λ estimates that were consistent with trends at non-horse areas elsewhere in the study region. Thus, AML max , as a whole, appeared to be set adequately in preventing adverse effects to sage-grouse populations. Results indicated 76%, 97%, and >99% probability of sage-grouse population decline relative to controls when horse numbers are 2, 2.5, and ≥3 times over AML max , respectively. As of 2019, horse herds exceeded AML max in Nevada, USA, by >4 times on average across all horse management areas. If feral horse populations continue to grow at current rates unabated, model projections indicate sage-grouse populations will be reduced within horse-occupied areas by >70.0% by 2034 (15-year projection), on average compared to 21.2% estimated for control sites. A monitoring framework that improves on estimating horse abundance and identifying responses of sage-grouse and other key indicator species (plant and animal) would be beneficial to guide management decisions that promote co-occurrence of horses with sensitive wildlife and livestock within landscapes subjected to multiple uses. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.

Nevada↗
USGS2022

Highly pathogenic avian influenza is an emerging disease threat to wild birds in North America

Prior to the emergence of the A/goose/Guangdong/1/1996 (Gs/GD) H5N1 influenza A virus, the long-held and well-supported paradigm was that highly pathogenic avian influenza (HPAI) outbreaks were restricted to poultry, the result of cross-species transmission of precursor viruses from wild aquatic birds that subsequently gained pathogenicity in domestic birds. Therefore, management agencies typically adopted a prevention, control, and eradication strategy that included strict biosecurity for domestic bird production, isolation of infected and exposed flocks, and prompt depopulation. In most cases, this strategy has proved sufficient for eradicating HPAI. Since 2002, this paradigm has been challenged with many detections of viral descendants of the Gs/GD lineage among wild birds, most of which have been associated with sporadic mortality events. Since the emergence and evolution of the genetically distinct clade 2.3.4.4 Gs/GD lineage HPAI viruses in approximately 2010, there have been further increases in the occurrence of HPAI in wild birds and geographic spread through migratory bird movement. A prominent example is the introduction of clade 2.3.4.4 Gs/GD HPAI viruses from East Asia to North America via migratory birds in autumn 2014 that ultimately led to the largest outbreak of HPAI in the history of the United States. Given the apparent maintenance of Gs/GD lineage HPAI viruses in a global avian reservoir; bidirectional virus exchange between wild and domestic birds facilitating the continued adaptation of Gs/GD HPAI viruses in wild bird hosts; the current frequency of HPAI outbreaks in wild birds globally, and particularly in Eurasia where Gs/GD HPAI viruses may now be enzootic; and ongoing dispersal of AI viruses from East Asia to North America via migratory birds, HPAI now represents an emerging disease threat to North American wildlife. This recent paradigm shift implies that management of HPAI in domestic birds alone may no longer be sufficient to eradicate HPAI viruses from a given country or region. Rather, agencies managing wild birds and their habitats may consider the development or adoption of mitigation strategies to minimize introductions to poultry, to reduce negative impacts on wild bird populations, and to diminish adverse effects to stakeholders using wildlife resources. The main objective of this review is, therefore, to provide information that will assist wildlife managers in developing mitigation strategies or approaches for dealing with outbreaks of Gs/GD HPAI in wild birds in the form of preparedness, surveillance, research, communications, and targeted management actions. Resultant outbreak response plans and actions may represent meaningful steps of wildlife managers toward the use of collaborative and multi-jurisdictional One Health approaches when it comes to the detection, investigation, and mitigation of emerging viruses at the human-domestic animal-wildlife interface.

Journal of Wildlife Management↗