ABSTRACT Despite litter size and kitten survival in mountain lions (Puma concolor) being well‐documented, there is a critical gap in the literature regarding the time that elapses between litter mortality and subsequent rebreeding in females. Here, we present observations from seven female mountain lions from two distinct study locations—the Black Hills of South Dakota and the Jemez Mountains of north‐central New Mexico—where female mountain lions lost litters and rebred shortly afterward. Our findings contribute novel data to the understanding of reproduction in mountain lions, including the shortest documented interval between litter loss and rebreeding (range: ≤ 4–94 days; mean: 46 days). These observations underscore the evolutionary pressures shaping sexual selection in mountain lions and highlight the significant physiological toll females endure as a consequence of infanticide and intraguild competition, with implications for population dynamics and fitness.

Abstract Conservation of migratory ungulate populations requires collaborative, large‐scale planning efforts that identify critical spatial components, habitat conditions, and resources necessary to support migratory populations. Yet our understanding of large herbivore migration ecology is limited for the southwestern United States, particularly in New Mexico. We assessed habitat characteristics within population‐level spring migration routes, stopover sites, and available reference locations for adult female elk ( Cervus canadensis ), mule deer ( Odocoileus hemionus ), and pronghorn ( Antilocapra americana ) from migratory herds in the southern San Juan Mountains in 2021–2022. Spring stopover sites for elk were characterized by taller browse and tree canopy heights compared to their migratory routes. Additionally, elk migration route habitats had minimal coarse woody debris and open understory compared to available reference locations. Although elk migration routes experienced a 48.5% higher overall extent of vegetation green‐up during spring migration periods (i.e., cumulative sum of the instantaneous rate of green‐up values) relative to available reference locations, the overall low values across site types suggest green‐up was low to moderate. Mule deer spring stopover sites were characterized by relatively flat terrain compared to their migration routes, which were located on ridgelines with sparse grass cover and were closer to agricultural areas compared to available reference locations. Relative to spring migration routes, stopover sites of pronghorn were defined by lower tree canopy heights and tree canopy cover, reduced cover and height of browse, lower understory cover, and more heterogeneous understory vegetation. In contrast to available reference locations, pronghorn migration routes had 70% lower instantaneous rate of green‐up values during the spring migration period and were located farther from mixed conifer forests. Additionally, aspen ( Populus tremuloides ) forests were found within pronghorn migration routes and stopover locations, although distances to aspen did not differ among site types. Our results can aid in directing habitat enhancement efforts toward migratory routes and stopover sites, facilitating the prioritization of management actions in areas with limited financial resources and competing land uses.

The Mexican gray wolf (hereafter Mexican wolf; Canis lupus baileyi) is a federally listed endangered subspecies whose population is recovering in Arizona and New Mexico, USA, and parts of northern Mexico. Predatory behavior of Mexican wolves has become increasingly studied in recent years following their initial reintroduction to the wild beginning in 1998, with wolves in the United States preying predominantly on elk (Cervus canadensis). Using global positioning system (GPS) collar data, we monitored 36 Mexican wolves from 24 packs to investigate GPS cluster locations formed by wolves to locate prey remains and identify prey composition from 2019 to 2023. During our 4-year study, we documented 2 cases of Mexican wolves killing and consuming free-roaming horses (Equus caballus) in New Mexico and Arizona. Although wolf predation on feral and native wild horses has been reported for many parts of Europe, Asia, and Canada, predation of feral horses by wolves has not been reported in the United States. As wolf populations continue to grow throughout North America, this behavior may become increasingly common in areas where the distributions of wolves and feral horses overlap. Feral horses may provide a novel food source for wolves, particularly in regions where native prey populations are more limited. We hope that these findings can help highlight the gap in knowledge that exists when considering wolf ecology, restructured food webs, and the potential role feral horses could play as wolf populations increase in the American West.

Population monitoring is essential to document recovery efforts for threatened and endangered species. Mexican wolves ( Canis lupus baileyi ) are an endangered subspecies of gray wolves that historically occupied large portions of the American Southwest and Mexico. Recently, the Mexican wolf population in the United States has been growing rapidly and traditional approaches for population monitoring (e.g., capture and radio collaring) are becoming difficult and expensive as wolves expand into new areas. We developed predictive models of pup‐rearing habitat (i.e., den and rendezvous sites) that could help guide future population monitoring efforts. We located 255 den sites and 129 rendezvous sites in Arizona and New Mexico, USA (1998–2023) using tracking collars and site visits. We sampled habitat conditions in wolf‐occupied regions of Arizona and New Mexico and fit logistic regressions to these data following a use–available study design to estimate resource selection functions (RSF) for den and rendezvous sites. We hypothesized wolves would select areas that offered greater physical protection, lower human‐disturbance, and access to reliable water sources for pup‐rearing but that the relative importance of these features would differ between the denning and rendezvous site seasons. Mexican wolves selected den sites at higher elevations in steeper and rougher terrain that were closer to permanent waterbodies but farther from rural roads. Selection of rendezvous sites was also associated with higher elevations and proximity to waterbodies but varied with availability of green leaf biomass on the landscape. While still highly predictive, our rendezvous site model was less predictive than our den model (Spearman's correlation averaged 0.81 [SE = 0.05] vs. 0.90 [SE = 0.03], respectively), possibly because water and green leaf biomass are more spatially diffuse and variable because of monsoonal rains during the rendezvous site season. Our results suggest that terrain features associated with physical protection and access to reliable water were most important in characterizing suitable pup‐rearing habitat for Mexican wolves. By predicting suitable den and rendezvous site habitat across portions of the Mexican Wolf Experimental Population Area, our models can help guide future population monitoring by reducing the total search area when surveying for wolves and increase the probability of detecting all members of a pack.

Accurate abundance estimates are critical for informed management of wildlife populations. In New Mexico, USA, minimum counts from aerial surveys are the primary basis for management decisions regarding desert bighorn sheep ( Ovis canadensis mexicana ); therefore, there is a need to assess methods that account for imperfect detection. Common survey methods for large mammals (i.e., sightability, double‐observer, and double‐observer sightability models) are known to result in biased estimates, but the presence of radio‐collared individuals within a population allows for estimation of residual heterogeneity. Consequently, we explored the use of hybrid double‐observer sightability approaches that account for residual heterogeneity when estimating abundance of desert bighorn sheep in the Fra Cristobal Mountains of New Mexico. We collected double‐observer sightability data for 167 desert bighorn groups across 3 surveys between December 2016 and November 2017 and compared abundance estimates under 5 modeling methods: a standard sightability model (M S ), a standard double‐observer sightability model (M DS ), a hybrid double‐observer sightability model incorporating a recapture‐type heterogeneity parameter (M R ), a hybrid double‐observer sightability model incorporating a mark‐type heterogeneity parameter (M H ), and a Lincoln‐Petersen estimator. Across all model types, group behavior (moving vs. stationary) and group size influenced detection the most, followed by vegetation class, terrain type, and proportion of obscuring vegetation cover. Standard sightability models produced higher and less precise abundance estimates than all double‐observer sightability models. Of the double‐observer sightability models, M R was better supported and estimated greater abundance than M H and accounted for more bias than M DS . Both M R and M H yielded greater precision than M S . The M R models produced an average detection probability of p = 0.72 (SE = 0.02) and abundance estimates of = 302 (95% CI = 262−385), = 290 (95% CI = 261−340), and = 352 (95% CI = 264−548) for the December 2016, May 2017, and November 2017 surveys, respectively. Lincoln‐Petersen estimates of abundance were greater than all double‐observer sightability models and similarly precise, but their usefulness is reduced given the requirement to permanently maintain a subset of animals with radio‐collars combined with the inability to incorporate information from factors influencing detection probability. Further, because residual heterogeneity models better estimate visibility bias, are flexible in their accommodation of radio‐collar data, and can be adapted to unique survey occasions, they present a viable and robust option for estimating desert bighorn sheep abundance.

Foraging time is a major component of ungulate activity budgets but can be limited by anti-predator behaviors (e.g., vigilance). Multitasking can reduce the nutritional costs of vigilance under heightened predation risk, but this may depend on the response of prey to risk from multiple predators across a complex spatiotemporal landscape. Mexican gray wolves (Canis lupus baileyi) and mountain lions (Puma concolor) are primary predators for elk (Cervus canadensis) in the Mexican wolf experimental population area in east-central Arizona and west-central New Mexico. We observed elk foraging across varying levels of wolf risk throughout all seasons and diel periods to quantify proportions of foraging, intense vigilance, and multitasking at the individual and herd levels. We quantified encounter and kill risk from Mexican wolves and mountain lions using habitat selection functions and utilization distributions. We modeled elk behaviors as functions of predicted risk for both predators in addition to temporal and environmental covariates and accounted for human presence. Our results indicate that individual elk reduced foraging in areas with higher predicted risk from Mexican wolves or mountain lions and increased intense vigilance and multitasking in areas with higher wolf risk. A reduction in the proportion of bedded elk in the herd during all diel periods under increased wolf risk supports previous findings. These results also suggest that elk compensate for higher intense vigilance and reduced foraging during foraging bouts by increasing cumulative foraging bouts per day at the cost of resting. Additionally, the probability of multitasking for individuals depended on an interaction between short- and long-term wolf risk, and the likelihood of intense vigilance was highest under the greatest combined spatial and temporal risk from wolves. This research provides insight into the fine-scale and complex behavioral responses of elk to their primary predators and implies a need for researchers to consider these non-consumptive effects in future studies of predator-prey dynamics.

Predation establishes risk, which can indirectly influence prey behavior and ecology. We evaluated the influence of Mexican gray wolves (Canis lupus baileyi) on habitat selection and spatiotemporal predator avoidance strategies of elk (Cervus canadensis). We fit 866 adult female elk with GPS collars across areas of varying wolf densities within the Mexican wolf experimental population area of eastern Arizona and western New Mexico between 2019−2021. Using step-selection functions we examined relative intensity of elk use in relation to landscape attributes, estimated predator/prey diel activity, and measures of risk. Risk metrics included predicted wolf presence, habitat openness, and predicted risky places modeled from attributes of locations where wolves killed elk. Wolf activity varied across seasons and increased midday and night in fall and monsoon seasons. Relative use by elk was best explained by incorporating an interaction between diel period and predicted risky places across all seasons. Elk utilized risky places more in times of nutritional deficit associated with high energetic demands of the third trimester pregnancy and lactation and when forage quality was best, during spring and monsoon season. Particularly, use of risky places increased at less risky times in areas with more established wolf presence, suggesting use of risky places varied relative to exposure to Mexican wolves. These behaviors highlight the importance of temporal avoidance when predators and prey are highly mobile and largely overlap in space. Our research suggests temporally responding to predictable and relatively static environmental characteristics associated with encounter and kill rates may better balance energetic trade-offs than anticipating changes in wolf activity or spatially avoiding areas with higher wolf presence. Thus, elk appear to be more willing to take chances and mitigate cursorial predation risk with a more immediate, reactive approach and make proactive trade-offs during the seasons they can best increase fitness.

Wildlife diseases have implications for ecology, conservation, human health, and health of domestic animals. They may impact wildlife health and population dynamics. Exposure rates of coyotes (Canis latrans) to pathogens such as Yersinia pestis, the cause of plague, may reflect prevalence rates in both rodent prey and human populations. We captured coyotes in north-central New Mexico during 2005-2008 and collected blood samples for serologic surveys. We tested for antibodies against canine distemper virus (CDV, Canine morbillivirus), canine parvovirus (CPV, Carnivore protoparvovirus), plague, tularemia (Francisella tularensis), and for canine heartworm (Dirofilaria immitis) antigen. Serum biochemistry variables that fell outside reference ranges were probably related to capture stress. We detected antibodies to parvovirus in 32/32 samples (100%), and to Y. pestis in 26/31 (84%). More than half 19/32 (59%) had antibodies against CDV, and 5/31 (39%) had antibodies against F. tularensis. We did not detect any heartworm antigens (n = 9). Pathogen prevalence was similar between sexes and among the three coyote packs in the study area. Parvovirus exposure appeared to happen early in life, and prevalence of antibodies against CDV increased with increasing age class. Exposure to Y. pestis and F. tularensis occurred across all age classes. The high coyote seroprevalence rates observed for CPV, Y. pestis, and CDV may indicate high prevalence in sympatric vertebrate populations, with implications for regional wildlife conservation as well as risk to humans via zoonotic transmission.

Ungulates commonly select habitat with higher forage biomass and or nutritional quality to improve body condition and fitness. However, predation risk can alter ungulate habitat selection and foraging behavior and may affect their nutritional condition. Ungulates often choose areas with lower predation risk, sometimes sacrificing higher quality forage. This forage–predation risk trade-off can be important for life history strategies and influences individual nutritional condition and population vital rates. We used GPS collar data from adult female mule deer (Odocoileus hemionus) and mountain lions (Puma concolor) to model mule deer habitat selection in relation to forage conditions, stalking cover and predation risk from mountain lions to determine if a forage-predation risk trade-off existed for mule deer in central New Mexico. We also examined mountain lion kill sites and mule deer foraging locations to assess trade-offs at a finer scale. Forage biomass and protein content were inversely correlated with horizontal visibility, hence associated with higher stalking cover for mountain lions, suggesting a forage-predation risk trade-off for mule deer. Mule deer habitat selection was influenced by forage biomass and protein content at the landscape and within home range spatial scales, with forage protein being related to habitat selection during spring and summer and forage biomass during winter. However, mule deer selection for areas with better foraging conditions was constrained by landscape-scale encounter risk for mountain lions, such that increasing encounter risk was associated with diminished selection for areas with better foraging conditions. Mule deer also selected for areas with higher visibility when mountain lion predation risk was higher. Mountain lion kill sites were best explained by decreasing horizontal visibility and available forage protein, suggesting that deer may be selecting for forage quality at the cost of predation risk. A site was 1.5 times more likely to be a kill site with each 1-meter decrease in visibility (i.e., increased stalking cover). Mule deer selection of foraging sites was related to increased forage biomass, further supporting the potential for a trade-off scenario. Mule deer utilized spatio-temporal strategies and risk-conditional behavior to reduce predation risk, and at times selected suboptimal foraging areas with lower predation risk.

With the intensity and frequency of wildfires increasing rapidly, the need to study the ecological effects of these wildfires is also growing. An understudied aspect of fire ecology is the effect fires have on parasite-host interactions, including ectoparasites that might be pathogen vectors. Although some studies have examined the impacts of fire on ticks, studies on other ectoparasites, including pathogen vectors, are rare. To help address this knowledge gap, we examined the abiotic and biotic factors that predict the likelihood and extent of parasitism of deer mice (Peromyscus maniculatus) by fleas within a landscape of unburned and recovering burned (>9 yr postfire) mixed conifer forests. We sampled 227 individual deer mice across 27 sites within the Jemez Mountains of northern New Mexico in 2022 and quantified measures of parasitism by fleas (primarily Aetheca wagneri). These sites were distributed in both unburned areas (n = 15) and recovering burned areas (n = 12), with the latter derived from 2 large fires, the Las Conchas fire (2011) and the Thompson Ridge fire (2013). Using these data, we tested for differences in prevalence, mean abundance, and mean intensity of fleas on deer mice, focusing on the predictive importance of host sex and fire history. We also created generalized linear mixed-effects models to investigate the best host and environmental predictors of parasitism by fleas. Approximately a decade postfire, we found minimal evidence to suggest that fire history influenced either the presence or intensity of fleas on deer mice. Rather, at the current forest-regeneration stage, the extent of parasitism by fleas was best predicted by measures of host sex, body condition, and the trapline's ability to accumulate water, as measured through topography. As host body condition increased, the probability of males being parasitized increased, whereas the opposite pattern was seen for females. Male mice also had significantly greater flea loads. Among potential abiotic predictors, the topographic wetness index or compound topographic index (a proxy for soil moisture) was positively related to flea intensity, suggesting larger flea populations in burrows with higher relative humidity. In summary, although fire may potentially have short-term impacts on the likelihood and extent of host parasitism by fleas, in this recovering study system, host characteristics and topographic wetness index are the primary predictors of parasitism by fleas.

AbstractPredator non‐consumptive effects (NCE) can alter prey foraging time and habitat use, potentially reducing fitness. Prey can mitigate NCEs by increasing vigilance, chewing‐vigilance synchronization, and spatiotemporal avoidance of predators. We quantified the relationship between Mexican wolf (Canis lupus baileyi) predation risk and elk (Cervus canadensis) behavior. We conducted behavioral observations on adult female elk and developed predation risk indices using GPS collar data from Mexican wolves, locations of elk killed by wolves, and landscape covariates. We compared a priori models to determine the best predictors of adult female behavior and multitasking. Metrics that quantified both spatial and temporal predation risk were the most predictive. Vigilance was positively associated with increased predation risk. The effect of predation risk on foraging and resting differed across diurnal periods. During midday when wolf activity was lower, the probability of foraging increased while resting decreased in high‐risk areas. During crepuscular periods when elk and wolves were most active, increased predation risk was associated with increased vigilance and slight decreases in foraging. Our results suggest elk are temporally avoiding predation risk from Mexican wolves by trading resting for foraging, a trade‐off often not evaluated in behavioral studies. Probability of multitasking depended on canopy openness and an interaction between maternal period and predation risk; multitasking decreased prior to parturition and increased post parturition in high‐risk areas. Openness was inversely related to multitasking. These results suggest adult female elk are altering the type of vigilance used depending on resource availability/quality, current energetic needs, and predation risk. Our results highlight potentially important, but often‐excluded behaviors and trade‐offs prey species may use to reduce the indirect effects of predation and contribute additional context to our understanding of predator–prey dynamics.

AbstractMycoplasma ovipneumoniae is a primary causative agent responsible for initiating polymicrobial pneumonia in bighorn sheep (Ovis canadensis). Infections of bighorn sheep populations are typically characterized by initial all‐age epizootics followed by long‐term periods of repressed juvenile (lamb) survival. Populations of bighorn sheep in New Mexico, USA, were thought to be free of this pathogen prior to 2017 but recent infection of multiple herds raised concerns regarding impacts on population size and juvenile:female ratios. Using aerial survey, survival, and disease sampling data in an exploratory framework, we (1) characterize age‐related differences in M. ovipneumoniae prevalence and seroprevalence, (2) quantify differences in lamb:ewe ratios pre‐ and post‐M. ovipneumoniae detection, and (3) investigate differences in survival between previously exposed and naïve individuals. From 2007 to 2022, we sampled 466 bighorn sheep across 19 populations in New Mexico for M. ovipneumoniae exposure. While the timing of initial herd infections varied across populations, one population sustained active infections for over 15 years. We found reduced juvenile:female ratios post M. ovipneumoniae exposure for both desert (O. c. mexicana) and Rocky Mountain (O. c. canadensis) bighorn sheep populations. Post‐exposure ratio declines ranged from 20% to 69%. Evaluation of population size and environmental condition effects on juvenile:female ratios indicated varying impacts for each subspecies. Notably, population size was negatively related to Rocky Mountain juvenile:female ratios only after populations were exposed to M. ovipneumoniae. Additionally, climatic conditions in the previous lambing season and pre‐parturition time frame were associated with juvenile:female ratios for Rocky Mountain populations, while juvenile:female ratios of desert bighorn appeared to only be affected by pre‐parturition climatic conditions. Kaplan–Meier survival estimation of previously exposed, but putatively recovered, individuals (n = 31) and naïve individuals (n = 70) revealed lower (75%; 95% CI: 62%–93%) but not statistically significant (p = 0.2) 1‐year survival rates for individuals that were seropositive but not actively infected, when compared to seronegative individuals (88%; 95% CI: 81%–97%). These results collectively suggest that following M. ovipneumoniae introduction, bighorn sheep populations in New Mexico could be limited by lamb survival.

Desert bighorn sheep (Ovis canadensis) populations often occur in remote areas at low densities, leading to gaps in knowledge of life history. In November 2011, we translocated 11 female desert bighorn sheep from the Fra Cristobal Mountains and 9 from Red Rock Wildlife Management Area (RRWMA) to the Peloncillo Mountains in southwestern New Mexico. In December 2012, we captured 21 adult females in the Peloncillo Mountains, 14 of which were recaptured from 2011. We fitted each animal with a very high frequency (VHF) collar and vaginal implant transmitter (VIT) to monitor for parturition. We captured 26 lambs (5 females, 7 males in 2012; 7 males, 7 females in 2013), recorded morphometric measurements and fitted lambs with VHF collars to monitor survival. Over the study, 14 lambs died, with 12 mortalities from predation, one from abandonment, and one from unknown causes. Lambing season was protracted over 3-4 months and survival was unrelated to birth timing. Body mass differences between sex varied by year, suggesting a connection to annual climate. Because most studies focus on captive animals with access to supplemental food, captive lambs may not be representative of free-ranging populations. Thus, we investigated morphological trends in a free-ranging population.

Esclarecer los factores que influyen en el tama & ntilde;o del & aacute;rea de campeo es fundamental para la ecolog & iacute;a y el manejo de lafauna silvestre, particularmente aquellas de inter & eacute;s para la conservaci & oacute;n, porque pueden proporcionar informaci & oacute;n sobre c & oacute;mo & eacute;stas utilizan su entorno. Por ejemplo, la variaci & oacute;n en el tama & ntilde;o del & aacute;rea de campeo puede estar relacionada con la competencia intraespec & iacute;fica y la organizaci & oacute;n social, los requerimientos energ & eacute;ticos en relaci & oacute;n con la productividad del h & aacute;bitat, la existencia de relaciones alom & eacute;tricas y la densidad poblacional. El lobo gris mexicano (Canis lupus baileyi) es una subespecie del lobo gris en peligro de extinci & oacute;n cuyo tama & ntilde;o de & aacute;rea de campeo no se ha estudiado. Examinamos los factores ecol & oacute;gicos y sociales relacionados con el tama & ntilde;o del & aacute;rea de campeo de 22 manadas de lobos mexicanos entre 2017 y 2021 en 4 per & iacute;odos de tiempo biol & oacute;gicos: anual, durante la formaci & oacute;n de guarida, despu & eacute;s de la formaci & oacute;n de guarida y sin guarida. Utilizamos el estimador del & aacute;rea de campeo denominado Modelo de Movimiento de Puente Browniano a un 95% y modelos lineales generalizados de efectos mixtos para evaluar estas relaciones. El tama & ntilde;o del & aacute;rea de campeo se correlacion & oacute; inversamente con la biomasa de ungulados estimada, que fue la variable que m & aacute;s influy & oacute; en el tama & ntilde;o del & aacute;rea de campeo en los per & iacute;odos biol & oacute;gicos anual y despu & eacute;s de la formaci & oacute;n de guarida. Las manadas m & aacute;s grandes presentaron & aacute;reas de campeo m & aacute;s grandes durante la formaci & oacute;n de guarida y despu & eacute;s de la formaci & oacute;n de guarida, mientras que las manadas con camadas m & aacute;s grandes tuvieron & aacute;reas de campeo m & aacute;s peque & ntilde;os durante la formaci & oacute;n de guarida. La profundidad de la nieve estuvo inversamente relacionada con el tama & ntilde;o del & aacute;rea de campeo durante la estaci & oacute;n sin guarida. Nuestros resultados indican que tanto los factores ecol & oacute;gicos como los sociales son importantes y que & eacute;stos var & iacute;an estacionalmente para determinar el tama & ntilde;o del & aacute;rea de campeo del lobo mexicano. El uso de un enfoque multiescala en estudios futuros sobre el & aacute;rea de campeo podr & iacute;a ayudar a determinar factores relevantes para las especies focales durante per & iacute;odos de tiempo con inter & eacute;s biol & oacute;gico.

First posted April 11, 2024 For additional information, contact: Associate Director, Ecosystems Mission AreaU.S. Geological Survey12201 Sunrise Valley Drive, MS 300Reston, VA 20192 Broadly distributed across the Western United States, ungulates (hooved mammals) play an important role in ecosystem function by affecting vegetation communities and forming the prey base for large carnivores. Additionally, ungulates provide economic benefits to regional communities through tourism and hunting and hold cultural significance for many Tribal communities. Many ungulates migrate seasonally between distinct summer and winter ranges to take advantage of spatially and temporally variable food sources and avoid threats such as predators and deep snow. Increasingly, these migrations are threatened by the growing human footprint and associated subdivisions, energy development, and increased traffic volume. Efforts to study ungulate populations and conserve their migrations received support in recent years from the U.S. Department of the Interior Secretarial Order No. 3362, which provided Federal support for enhancing habitat quality for ungulates across the Western States. In response to Secretarial Order No. 3362, the U.S. Geological Survey (USGS) established the Corridor Mapping Team, a collaboration among USGS and participating State and Federal wildlife management agencies and numerous Tribal Nations. Together, the Corridor Mapping Team maps ungulate migrations throughout the Western United States in the USGS "Ungulate Migrations of the Western United States" report series. This report (volume 4) details migrations and seasonal ranges from 31 new herds throughout nine Western States. Additionally, this report includes updates to two herds published in previous reports. Including this report, the report series has provided the mapped migrations and seasonal ranges of 182 unique herds and has provided a map-based inventory of the documented ungulate migrations across the Western United States for biologists, managers, policy makers, and conservation practitioners. This report also discusses how the mapping efforts associated with the Corridor Mapping Team can be used to guide management and policy regarding renewable energy development and ungulate disease, specifically chronic wasting disease, in the Western United States.

Bighorn sheep (Ovis canadensis) are influenced by infectious diseases. Although Mycoplasma ovipneumoniae has been the main focus of bighorn sheep managers since early 2010, other pathogens may also influence bighorn sheep populations. We sampled desert bighorn sheep (Ovis canadensis mexicana) captured for a study on the Cabeza Prieta National Wildlife Refuge in southwestern Arizona, USA, 2001-2005, for a suite of pathogens: bluetongue (BT), epizootic hemorrhagic disease (EHD), parainfluenza 3, bovine respiratory syncytial virus, Clamydia, seven Leptospira serovars, bovine herpesvirus 1 (causative agent of infectious bovine rhinotracheitis), bovine viral diarrhea virus, and bovine respiratory syncytial virus. We recorded evidence of exposure to seven of these pathogens, with two Leptospira serovars (hardjo and bratislava), five strains of BT, and two strains of EHD detected. Seroprevalence rates of detected pathogens varied between 12-49%. We observed high levels of co-occurrence for EHD and BT. These results highlight that multiple pathogens may influence desert bighorn sheep populations. These data also provide historical context to pathogen exposure for a region where few such data are available.

Expansion of feral burro (Equus asinus) populations across the southwestern United States is causing human-wildlife conflicts including rangeland degradation, competition with livestock and native species, and burro-vehicle collisions. On the Fort Irwin National Training Center (NTC) in California, feral burros interfere with military training and are involved in vehicle collisions and other conflicts (e.g., burros blocking access to buildings). Limited data on burro movements and resource use poses a challenge for the development of management plans and mitigation strategies. We estimated home range size, second- and third-order seasonal resource selection, and water dependency of 10 adult female feral burros fitted with global positioning system (GPS) collars on the NTC from November 2015 to April 2017. Mean 95% autocorrelated kernel home range size of female burros (253.9 +/- 30.7 km(2) [SE]) did not differ among seasons or between burros that resided close to or far from urban areas. Burros selected areas closer to water in all seasons and at both spatial scales, but selection was stronger in the dry season and at the landscape scale. When available, burros strongly selected for areas closer to urban areas. Burros consistently selected for areas with green forage and at lower elevations, but selection for other topographical features was variable. Water use patterns were consistent with the resource selection results. Burros visited water sources twice as often (every 22.2 +/- 6.3 hr) during the hot-dry season (Apr-Oct) compared to the cool-wet seasons (Nov-Mar; 2015: 45.9 +/- 21.0; 2016: 39.7 +/- 9.3 hr). Our results suggest that urban areas, and resources therein, and water sources have the biggest influence on burro resource selection, and management plans could focus mitigation programs on these areas.

Colonization of urban areas by synanthropic wildlife introduces novel and complex alterations to established ecological processes, including the emergence and spread of infectious diseases. Aggregation at urban resources can increase disease transfer, with wide-ranging species potentially infecting outlying populations. The garrison at the National Training Center, Fort Irwin, California, USA, was recently colonized by mange-infected coyotes (Canis latrans) that also use the surrounding Mojave Desert. This situation provided an ideal opportunity to examine the effects of urban resources on disease dynamics. We evaluated seasonal space use and determined the influence of anthropogenic subsidies, water sources, and prey density on urban resource selection. We found no difference in home range size between healthy and infected individuals, but infected residents had considerably more spatial overlap with one another than healthy residents. All coyotes selected for anthropogenic subsidies during all seasons, while infected coyotes seasonally selected for urban water sources, and healthy coyotes seasonally selected for urban areas with greater densities of natural prey. These results suggest that while all coyotes were selecting for anthropogenic subsidies, infected resident coyotes demonstrated a greater tolerance for other conspecifics, which could be facilitating the horizontal transfer of sarcoptic mange to non-resident coyotes. Conversely, healthy coyotes also selected for natural prey and healthy residents exhibited a lack of spatial overlap with other coyotes suggesting they were not reliant on anthropogenic subsidies and were maintaining territories. Understanding the association between urban wildlife, zoonotic diseases, and urban resources can be critical in determining effective responses for mitigating future epizootics.

Competition can affect species assemblages, population dynamics of competitors, and ecosystem processes. Understanding interspecific competition involves considering multidimensional factors that relate directly to the niche of competitors. For coexistence of species to occur, overlap on an important niche axis, such as diet, habitat, or space, must be accompanied by avoidance on another axis. Observed patterns of resource partitioning may have resulted from past competitive interactions, which reflect the realized rather than fundamental niches of competitors. Moreover, niche space and resultant overlap in resource use by competitors may differ seasonally, thereby leading to variation in competitive outcomes. This chapter describes interactions of black-tailed and mule deer (i.e., deer) with American bison; collared peccary; domestic livestock; elk; exotic animals, feral burros, horses, and pigs; moose; mountain sheep; pronghorn; and white-tailed deer. A changing climate holds potential to adversely affect deer across their distribution. Negative effects on forage quality and patterns of green-up may affect productivity of populations and alter migratory patterns. Drought in summer and amount and timing of spring rainfall may influence the distribution of deer and affect survival, especially in desert ecosystems. How such changes affect competitive interactions of mule deer with other ungulates is uncertain, and requires further research.