Abstract Many mammalian neonates adopt behavioral survival strategies, such as predator avoidance and close parental proximity, to mitigate mortality risks during early development. For White-tailed Deer (Odocoileus virginianus), these strategies progress across three behavioral stages: hider, follower, and post-follower, each with distinct risks. Despite the critical effect of each stage on survival, the influence of intrinsic traits, landscape features, and anthropogenic activity across these stages remains poorly understood. We addressed this knowledge gap by evaluating factors influencing survival in 399 neonate White-tailed Deer across three behavioral stages in two landscapes in Missouri, USA, from 2015 to 2019. Mortality risks varied significantly across stages using time-dependent and competing risks hazard models. In the hider stage, higher birth mass reduced natural mortality risks, while greater trail density in forested areas lowered risk, likely by altering predator movement. During the follower stage, male neonates had higher mortality risks than females, likely attributable to increased activity levels in males. In the post-follower stage, road density increased mortality risk in fragmented landscapes, possibly due to predator presence and vehicle collisions. These results indicate that neonate survival depends on the dynamic interaction between intrinsic and environmental factors, which vary across developmental stages. By linking survival to behavioral stages, our findings provide insights into how early-life strategies mediate the effects of landscape and individual traits, offering broader insights into how species adapt to human-altered ecosystems. Understanding the interplay of behavioral stages and environmental risks can contribute to ecological frameworks for understanding species adaptations to human-altered and rapidly changing ecosystems.
Abstract High ambient temperatures (Ta) pose a significant challenge to small endotherms that rely on limited water reserves to thermoregulate via evaporative cooling and are exacerbated for species inhabiting poorly insulated microsites. We used flow-through respirometry to investigate the thermoregulatory strategies and capacities of nonreproductive female Yuma Myotis (Myotis yumanensis) from one of the hottest areas of their range. Based on our physiological data and the NicheMapR biophysical model, we also calculated the evaporative cooling requirements and dehydration risk of these females when roosting in artificial structures during a heatwave in 2021 (modeled results) and during the warmest day of our study (measured results). Our results indicated that non-reproductive female M. yumanensis can tolerate a maximum Ta of 44 °C in dry air, adopting a thermoconforming strategy, possibly due to evaporative cooling restrictions imposed by their low water reserves. Our results allude to M. yumanensis using thermal gradients within roosts to avoid high roost temperatures and demonstrate that bats roosting in a South-facing artificial roost exposed to high solar radiation would have faced lethal dehydration during the 2021 heatwave. Our results underscore the importance of natural roosts in the landscape and highlight designing artificial roosts that offer a wide thermal gradient to allow the persistence of this species during current extreme climatic events.
Abstract Den selection is critical to reproductive success and offspring survival in many mammal species, but little is known about den site selection by wild coyotes (Canis latrans) outside of urban contexts. We examined the third- and fourth-order habitat characteristics of 42 Coyote dens in Elk Island National Park, a protected natural area in central Alberta, Canada. Using resource selection functions, we evaluated 3 hypotheses: that coyotes select dens based on (i) physical den suitability; (ii) security from predators, people, or dogs; and (iii) access to food and water resources. Coyotes exhibited strong fourth-order selection for dens with cohesive, inorganic soils and steep slopes that promote structural integrity and drainage. Structural supports such as roots and abandoned but persisting Beaver (Castor canadensis) infrastructure were common. We found limited evidence of selection for features that promoted security, contrasting other studies that found security to be an important predictor of den sites. We found no evidence for selection based on local resource availability. Our findings indicate that fine-scale habitat features related to den stability are the primary drivers of den site selection in wild coyotes in this ecosystem and suggest that den selection is flexible and context-dependent in response to local environmental pressures.
Abstract Prey naivety is a major consideration in the recovery of endangered populations, particularly when reintroduction sites house predators with which prey have no prior exposure. Since the eradication of rinderpest in the early 2000s, population growth of the Critically Endangered Hirola (Beatragus hunteri) has been suppressed due to a combination of predation and habitat loss stemming from the conversion of grassland to shrubland. We expected that Hirola within a predator-free sanctuary would relax their anti-predator responses over time, particularly with respect to proactive behaviors like vigilance when compared to individuals from the surrounding Ishaqbini Community Conservancy (where predators are present). In 2 sampling periods (2013 to 2015, and 2020 to 2021), we conducted focal observations to quantify a proactive anti-predator response (time spent vigilant) and 3 reactive anti-predator responses (flight distance, time spent fleeing, flight speed) for Hirola groups within the 2 settings. Contrary to our central hypothesis, vigilance did not decline over time for Hirola from the predator-proof sanctuary. Instead, vigilance was maintained at approximately constant levels from 2013 to 2015 to 2020 to 2021, both for individuals in the sanctuary and individuals in the conservancy. Although flight distance did not differ between experimental settings, Hirola in the conservancy fled a simulated predator, Lion (Panthera leo), via roar playbacks ca. 5 times as quickly as Hirola within the sanctuary. Whether Hirola reintroduced from the predator-proof sanctuary experience increased mortality therefore could depend on whether and how effectively vigilance reduces predation risk. We recommend (i) reintroducing individuals to areas with low predator densities and (ii) regular monitoring of behavior and survivorship following release to enhance the outcome of future reintroductions, and to better understand how proactive and reactive anti-predator behaviors differentially shape individual survival.
Until the onset of the Anthropocene, glacial cycles have been an important driver of species distributions through much of time, often resulting in cycles of increasing and decreasing demographic trends. Here, we assay thousands of nuclear loci across multiple individuals representing 4 Microtus vole species to assess both inter- and intra-specific population structure, as well as phylogenetic and demographic histories. First, phylogenetic analyses recovered M. pinetorum as the outgroup, followed by M. ochrogaster, and the most recent relationship between M. montanus and M. drummondii. Next, all 4 vole species harbored substantially divergent genomes, and an absence of interspecific hybrids, suggesting that these species are pre- and/or postzygotically isolated. Assessing divergence across markers, we recovered site-frequency spectra consistent with directional selection and/or signatures of allopatric speciation among species. While we recovered no intraspecific structure among M. pinetorum samples, population structure was evident within M. ochrogaster, M. montanus, and M. drummondii. We inferred effective population sizes for these species over the past 500,000 yr that suggest both independent and correlated demographic histories over 6 glacial cycles. Trends in population size were similar for M. montanus and M. ochrogaster, which increased in size from similar to 300,000 to 150,000 yr ago before declining since then. In contrast, M. pinetorum and M. drummondii increased from similar to 150,000 yr ago. These demographic histories were likely shaped by changing niche availability for each species over glacial and interglacial periods. Ice ages have repeatedly reshaped where animals live, expand, and decline. We use thousands of genetic markers across many individuals representing 4 Microtus vole species, and report that they are strongly differentiated genomically and no evidence of recent hybridization. Tracing demography over the last 6 major glacial cycles recovered inverse relationships in which M. montanus and M. ochrogaster expanded during cooler periods, while M. pinetorum and M. drummondii showed inverse relationships during the same period of time. Together, these results show that even closely related mammals can respond very differently to the same climatic events.
Optimal foraging theory predicts that animals should reduce energy expenditure and maximize fitness by establishing home ranges in areas with abundant, high-quality forage. However, ungulates may not select optimal foraging habitat when behavior is driven by site fidelity. On Vermejo Park Ranch, New Mexico, managers translocated American Bison (hereafter, bison) to high elevations to reduce historically heavy grazing in lower elevations and to distribute the ecological effects of grazing across the broader landscape. We hypothesized that: (i) home range size is driven by forage abundance and quality; but that (ii) site fidelity can result in suboptimal selection of home ranges in areas with lower forage abundance and quality. We estimated space use and resource selection of free-roaming GPS-collared bison occupying lower elevation sites of historical use and bison translocated to higher elevations to evaluate drivers of home range size and selection. Home range size was strongly negatively influenced by forage abundance. However, without translocation, bison exhibited fidelity to areas of historical use and selected seemingly suboptimal home ranges with lower forage biomass. Conversely, bison that established home ranges following translocation to higher elevations selected home ranges with greater forage biomass. Greater forage biomass enabled bison to use smaller home ranges, increasing spatial efficiency and cohesion. Bison on Vermejo that were not translocated by managers established home ranges at lower elevations despite the availability of higher quantity and quality (nitrogen yield) of forage at higher elevations. Thus, home range selection appeared to be guided by site fidelity rather than foraging optimally across the larger landscape. For managed ungulates, translocation may facilitate access to superior resources and eventually begin to restore knowledge of migratory routes and seasonally abundant forage.
Abstract Rapid climate changes are reshaping ecological communities in montane environments. Among those most strongly impacted are cold-adapted organisms that may experience thermal stress at moderate temperatures. The importance of facultative behavioral changes to altered abiotic resources like water, shade, and snow is well documented. However, behavioral patterns of spatial selection may change, particularly for cold-adapted species during summer months. We examine how high summer temperatures affect the behavior of mountain goats (Oreamnos americanus), a cold-adapted species with a Holocene distribution closely associated with periglacial environments in western North America. We hypothesized that habitat use by mountain goats during summer months is modulated by high temperatures, leading to increased selection for habitats that offer thermal refuge, including snow. We evaluated resource selection at 2 spatial scales: within the home range and at 4-h movement steps. During the warmest 15% of summer days, at the home range scale, mountain goats increased use of areas with lower solar radiation, higher elevations, locations further from predator escape terrain, and areas closer to human infrastructure. Contrary to expectations, mountain goats exhibited only modest selection for proximity to snow, and selection further decreased at peak temperatures at the home range scale. At the fine scale (4-h steps), individuals selected for relatively lower elevation and increased solar exposure during the warmest periods. These results suggest that avoidance of thermal radiation may be more effective through changes in behavior at the home range scale. Importantly, we document changes in intrinsic behaviors such as seeking safety from predators in steep terrain during the warmest days. As montane environments continue to warm rapidly, understanding changes in resource use during the warmest periods today offers an invaluable lens for understanding challenges for populations tomorrow.
The Black-tailed Jackrabbit (Lepus californicus) and Desert Cottontail (Sylvilagus audubonii) inhabit arid and semi-arid areas of North America. These species play an essential ecological role as prey, plant consumers, and game species. Their population density is affected by changes in climatic factors, with the expectation that-in most cases-a positive relationship exists between population density and precipitation, temperature, and photoperiod; and a negative relationship with wind speed. However, population density occasionally shows no relation to these factors or is contrary to expectations. Our study sought to determine the relationship between Black-tailed Jackrabbit and Desert Cottontail population densities and climatic factors, including precipitation, temperature, photoperiod, and wind speed in a semi-desert area of the state of Chihuahua, adjacent to the M & eacute;danos de Samalayuca Natural Protected Area, Mexico. From December 2022 to November 2023, the population density of both species was determined by monthly quantification using fecal pellet counts. Monthly data on environmental factors were obtained using meteorological stations near the site. Subsequently, relationships between the variables were established through linear models. Black-tailed Jackrabbit population density was found to have a negative relationship with photoperiod and total precipitation and a positive relationship with temperature and general wind speed. Desert Cottontail population density showed no relationship to these factors. Our findings underline that Black-tailed Jackrabbit populations are sensitive to climatic factors. However, the Desert Cottontail seems to respond to other ecological factors, highlighting variability in the adaptive strategies of these species in arid environments. We analyzed how climate affects the population density of 2 lagomorphs in a Mexican semi-desert. Black-tailed jackrabbits showed clear climatic responses, while desert cottontails did not, suggesting contrasting ecological strategies in arid environments. La liebre cola negra (Lepus californicus) y el conejo del desierto (Sylvilagus audubonii) habitan en zonas & aacute;ridas y semi & aacute;ridas de Am & eacute;rica del Norte. Estas especies desempe & ntilde;an un papel ecol & oacute;gico esencial como presas, consumidores de plantas y especies cineg & eacute;ticas. Su densidad poblacional se ve afectada por cambios en los factores clim & aacute;ticos, con la expectativa de que, en la mayor & iacute;a de los casos, exista una relaci & oacute;n positiva entre la densidad poblacional y la precipitaci & oacute;n, la temperatura y el fotoperiodo, y una relaci & oacute;n negativa con el viento. Sin embargo, ocasionalmente la densidad no muestra relaci & oacute;n con estos factores o presenta una relaci & oacute;n contraria a la esperada. Nuestro estudio tuvo como objetivo determinar la relaci & oacute;n entre la densidad poblacional de la liebre cola negra y del conejo del desierto con los factores clim & aacute;ticos de precipitaci & oacute;n, temperatura, fotoperiodo y viento en una zona semides & eacute;rtica del estado de Chihuahua, que es adyacente al & Aacute;rea Natural Protegida M & eacute;danos de Samalayuca, M & eacute;xico. Desde diciembre de 2022 hasta noviembre de 2023, se determin & oacute; la densidad poblacional de ambas especies mediante conteos mensuales utilizando el m & eacute;todo de conteo de pellets fecales. Los datos mensuales de los factores ambientales se obtuvieron a trav & eacute;s de estaciones meteorol & oacute;gicas cercanas al sitio. Posteriormente, se establecieron las relaciones entre las variables mediante modelos lineales. Se encontr & oacute; que la densidad poblacional de la liebre cola negra tiene una relaci & oacute;n negativa con el fotoperiodo y la precipitaci & oacute;n total, y una relaci & oacute;n positiva con la temperatura y el viento en general. La densidad poblacional del conejo del desierto no mostro una relaci & oacute;n con los factores evaluados. Nuestros hallazgos subrayan que las poblaciones de liebres cola negra son sensibles a los factores clim & aacute;ticos. Sin embargo, los conejos del desierto parecen responder a otros factores ecol & oacute;gicos, lo que resalta la variabilidad en las estrategias adaptativas de estas especies en ambientes & aacute;ridos.
The study of the substructure of small mammal populations has contributed to many foundational concepts in population biology. The contemporary model, summarized in Anderson's Resident Fitness Hypothesis, posits that resident small mammals have site tenacity, behaviorally resist intruders, and female offspring tend to be philopatric but young males leave their natal area. To evaluate this model, we analyzed 3 long-term data sets for 3 rodent species from 3 US states, totaling 34,536 animals across 40+ yr of study. The expectation of site tenacity with fixed home ranges was not supported because the majority of rodents (53.9%) were trapped only during a single month, and only 21.8% were caught 1 mo later. Similarly, the expectation that residents resist intruders was unsupported because 60.5% of initial captures were adults. Multiple logistic regression revealed that females had increased predicted probability of recapture for all species, and, for both vole species, the predicted probability of recapture increased with each gram of body mass at initial capture. These results provide little support for the expectation of offspring persistence near natal areas. Taken together, the resident fitness hypothesis is not well supported in these populations of grassland rodents. Movements of some other vertebrate populations, in association with food abundance, have been modelled in L & eacute;vy flights and Brownian motion. It is possible that movement patterns of rodents in these 6 populations derive from 1 or a combination of these strategies. After analyzing 40+ yr of capture-mark-release data for 3 grassland rodents from 3 US states, we find little support, at the population level, for the resident fitness hypothesis: that most recruits are young and female and that residents are site tenacious and resist intruders.
Understanding how arboreal mammals partition vertical space is essential to accurately characterize tropical forest communities, yet most camera trap surveys focus on the forest floor, or pair canopy and ground surveys. While canopy camera trapping is revealing new insights about arboreal mammals, sampling at a single height at each sampling point may obscure patterns in community structure. To address this gap, we developed a "camera column" technique, deploying 3 vertically aligned cameras at ground, understory-midstory, and canopy levels across 3 survey areas in Lomami National Park and its buffer zone, Democratic Republic of the Congo. We used this method to evaluate the species richness, community composition, and vertical habitat use of non-volant mammals. We identified 47 mammal taxa, including 8 outside their documented geographic range. Species accumulation curves showed that pooling detections across strata increased estimated richness relative to single-stratum sampling. However, pairwise pooling of strata to produce rarefaction curves revealed that combining ground and canopy cameras can sufficiently estimate species richness, suggesting redundancy in understory detections. Ordination analyses and height-distribution data revealed strong vertical structuring of mammal communities, with understory detections overlapping both terrestrial and canopy assemblages and capturing transitional habitat use. Notably, one-quarter of the arboreal taxa favored the understory-midstory level, indicating that reduced-strata surveys may mischaracterize vertical habitat use and bias analyses informed by presence/absence data. Our results demonstrate that while ground-canopy camera combinations may approximate species richness, full vertical sampling is necessary to accurately interpret community structure and ecological roles of species. Multi-strata camera columns provide a scalable approach for biodiversity assessment and conservation monitoring in structurally complex tropical forests.
We identify patterns of sexual dimorphism in the 2 extant colugo genera. Females exhibit greater skull size (PC1) only in Galeopterus, and toothcomb dimorphism is only found in Cynocephalus. We characterize these distinctions and discuss their evolutionary implications. This study investigates body size and sexual dimorphism in the 2 extant genera of dermopterans, the Sunda Colugo (Galeopterus variegatus) and Philippine Colugo (Cynocephalus volans). These are poorly studied mammal species and important taxa for understanding primate origins because they are the only extant members of Dermoptera, the sister taxon to Primates (together forming Primatomorpha). Through comprehensive analyses of craniodental datasets, we confirm genus-differences in general morphology and identify distinct patterns of sexual dimorphism. Our results demonstrate female-biased size dimorphism in Galeopterus crania, with females exhibiting larger mean values for multiple traits associated with gross skeletal size compared to males. Conversely, such cranial size dimorphism is reduced or absent in Cynocephalus. However, dental dimorphism is present in Cynocephalus; males have more tines on the first 2 incisors of their tooth comb, adding another dimension to the differences in dental traits between the Philippine and Sunda genera. These findings highlight a case of female-biased dimorphism in euarchontan mammals and emphasize the necessity of treating the extant colugo genera as fundamentally distinct, having undergone independent evolution over the last approximately 11-20 million years. Our results offer unique insights into the evolution of sexual dimorphism in primatomorphans.
In variable environments, animals can remain in place and tolerate changes or move to areas with favorable conditions. Species must balance the costs and benefits of site fidelity and behavioral plasticity in acclimating to rapidly changing environments. We investigated winter fidelity and behavioral plasticity of the Teshekpuk Caribou Herd (TCH) in Alaska. Using GPS telemetry data for 192 female Caribou (Rangifer tarandus) from 2004 to 2021, we identified patterns of winter distribution and how they changed compared to reports from 1990 to 2015. We investigated fidelity to wintering areas by comparing observed use of wintering areas with expectations based on area, distance, and sociality. We then examined intrinsic and extrinsic factors correlated with TCH winter distribution patterns using generalized additive mixed models to better understand how resources may influence use of wintering areas for the herd. Caribou used the same 4 wintering areas reported in prior studies, but increased use of the eastern wintering areas recently. TCH Caribou appeared to balance site fidelity and behavioral plasticity. Caribou exhibited some winter fidelity, with reuse of winter areas exceeding expectations, but still often changed wintering areas across years. Distribution among wintering areas varied with both intrinsic and extrinsic factors including summer and fall weather and, to a lesser extent, pregnancy, age, forage condition, and insect harassment. Weather variables had strong effects, with warmer fall air temperatures and lower precipitation corresponding to increased likelihood of animals forgoing migration to the southern mountains and instead overwintering on northern coastal plain tundra. Pregnant Caribou also were more likely to remain on the coastal plain overwinter. The flexibility of Caribou exhibiting both winter fidelity and plasticity may enhance robustness to environmental changes, but increased use of areas near industrial development emphasizes the importance of continued monitoring. Researchers should consider fidelity and behavioral plasticity across scales to inform effective management under changing conditions.
African savannas are experiencing an array of human-induced changes, including reductions and extirpations of large mammalian herbivores. The outcomes of these changes will be at least partially dependent on the functional responses of species that persist, including changes to plant-herbivore interaction networks. However, experimental tests of how ecological context, season, and competition jointly regulate foraging behaviors of large mammals are sparse. Therefore, we combined dietary DNA metabarcoding and a long-term herbivore-exclusion experiment in semi-arid Kenyan savanna to understand how a small browsing antelope (Guenther's Dik-dik, Madoqua guentheri, similar to 5 kg) responds to the absence of larger herbivores across seasons (e.g., wet vs dry) and sites (e.g., mesic vs xeric). We hypothesized that: (i) dik-dik diets would differ from those of co-occurring large browsers due to size-based differences in forage selection and accessibility; (ii) exclusion of larger herbivores would increase dik-dik activity and enable them to select high-quality browse, consistent with competitive release; and (iii) this selective foraging by dik-dik would suppress the growth and recruitment of their preferred woody food species. Consistent with our hypotheses, dik-dik diets differed significantly from co-occurring-but much larger-mixed-feeders, including the African Savanna Elephant (Loxodonta africana) and Impala (Aepyceros melampus). Dik-dik foraged selectively according to plant nutritional properties, especially protein content, and they avoided long-spined Acacia species, particularly during dry seasons and at the xeric site. In the absence of larger herbivores, dik-dik activity increased >2-fold, and they increased selectivity for the most nutritious, least-defended Acacia species. Shifts in selectivity due to competitive release were strongest under resource-scarce conditions, including dry seasons and xeric environments, amplifying local impacts of large-herbivore losses on savanna plant communities. Finally, in the absence of larger browsers, dik-dik suppressed the growth of their preferred species (Acacia mellifera), but only at the xeric site. Together, these results provide strong evidence that dik-dik exhibit flexible foraging behavior in response to larger herbivores, especially in resource-scarce conditions. If large herbivores are extirpated, subsequent diet shifts by dik-dik may suppress long-term plant diversity in this savanna.
Captive husbandry is a cornerstone of modern Caribou (Rangifer tarandus subspecies) conservation (e.g., captive rearing) and research in North America. Husbandry protocols have long emphasized feeding and nutrition programs, but information on health metrics-such as vital signs essential for evaluating animal health-is more limited, especially for young Caribou. We documented vital signs (i.e., body temperature, heart rate, and respiratory rate) of n = 8 hand-reared Caribou calves, each day, from 0 to 23 wk of age. We used multilevel, mixed-effects regression models to evaluate: (i) how vital signs changed as calves grew; and (ii) whether calves compensated (as indicated by changes in vital signs) for physiological perturbations (i.e., changes from homeostasis such as elevated body temperature). We excluded data from 1 calf that had a chronic illness; among healthy, juvenile Caribou in our study, mean (±SE) heart rate was 89 ± 0.7 beats/min, respiratory rate was 19 ± 0.2 breaths/min, and body temperature was 38.9 ± 0.01 °C. Heart rate, respiratory rate, and body temperature decreased as calf age and body mass increased; increasing calf age was a better predictor of heart rate, respiratory rate, and body temperature than body mass. Caribou calves exhibited physiological compensation for increasing body temperature by increasing heart rate and respiratory rate. Heart rate also increased as a function of increasing respiratory rate. Our findings for age-specific vital signs in Caribou calves can serve as baselines for future physiology studies and captive-rearing efforts that may enhance early detection and treatment of illness in captive Caribou.
Solitary species are defined by the tendency for adults to live alone. Although this serves to distinguish taxa that live in groups from those that do not, it overlooks considerable unappreciated variation in the behavior of species identified as solitary. As part of ongoing efforts to understand behavioral variation among tuco-tucos (subterranean rodents in the genus Ctenomys), we used radiotelemetry to characterize spatial and social relationships among adults in a previously unstudied species, C. scagliai, that occurs in Monte Desert habitat in northwestern Argentina. Our findings indicate that this species is solitary, providing an important basis for comparisons with other social and solitary species of tuco-tucos. Solitary species are defined by the tendency for adults to live alone. Spatial relationships among individuals, however, can vary markedly across solitary taxa, including differences in the degree and frequency of spatial overlap that may influence the potential for social interactions among conspecifics. As part of long-term studies of behavioral variation among tuco-tucos (Rodentia: Ctenomyidae), we characterized patterns of space use within a population of Ctenomys occurring in sparsely vegetated Monte Desert habitat near Amaicha del Valle, Tucum & aacute;n Province, Argentina. Analyses of mitochondrial Cytb sequences confirmed the assignment of these animals to C. scagliai, making them part of the opimus subclade within the genus Ctenomys. Radiotelemetry data revealed that members of the study population were solitary, with effectively no overlap of home ranges occupied by different adults. Comparisons of spatial relationships in this population and a population of a second solitary species (C. coludo) from a more heavily vegetated Monte habitat near Anillaco, La Rioja Province, Argentina revealed that mean home range size was greater but that both mean home range overlap and mean percentage of the home range used on a daily basis were smaller for C. scagliai. These differences are expected to have important implications for the frequency of potential social interactions in C. scagliai versus C. coludo. At the same time, the solitary behavior of the population C. scagliai at Amaicha creates critical opportunities for comparative studies of differences in social organization between these animals and the group-living C. opimus. Las especies solitarias se caracterizan por la tendencia de los adultos a vivir solos. Sin embargo, las relaciones espaciales entre individuos pueden variar notablemente entre taxones solitarios, incluyendo diferencias en el grado y la frecuencia de solapamiento espacial que pueden influir en el potencial de interacciones sociales entre conespec & iacute;ficos. Como parte de estudios a largo plazo sobre la variaci & oacute;n conductual en tuco-tucos (Rodentia: Ctenomyidae), caracterizamos los patrones de uso del espacio en una poblaci & oacute;n de Ctenomys que habita un entorno de desierto del Monte con vegetaci & oacute;n escasa, cerca de Amaicha del Valle, provincia de Tucum & aacute;n, Argentina. Los an & aacute;lisis de secuencias mitocondriales de Cytb confirmaron la asignaci & oacute;n de estos animales a C. scagliai, formando parte del subclado opimus dentro del g & eacute;nero Ctenomys. Los datos de radiotelemetr & iacute;a revelaron que los miembros de esta poblaci & oacute;n eran solitarios, con un solapamiento pr & aacute;cticamente nulo entre las & aacute;reas de actividad ocupadas por distintos adultos. La comparaci & oacute;n del uso del espacio entre esta poblaci & oacute;n y una poblaci & oacute;n de una segunda especie solitaria (C. coludo) procedente de un h & aacute;bitat de Monte con mayor cobertura vegetal cerca de Anillaco, provincia de La Rioja, Argentina, mostr & oacute; que el tama & ntilde;o medio del & aacute;rea de actividad era mayor en C. scagliai, pero que tanto el solapamiento entre las & aacute;reas de actividad como su porcentaje utilizado diariamente eran menores en C. scagliai. Se espera que estas diferencias tengan implicancias importantes en la frecuencia de interacciones sociales potenciales entre C. scagliai frente a C. coludo. Al mismo tiempo, el comportamiento solitario de la poblaci & oacute;n de C. scagliai en Amaicha genera oportunidades clave para estudios comparativos sobre las diferencias en la organizaci & oacute;n social entre esta especie y la especie social C. opimus.
The International Code of Zoological Nomenclature provides that if a name first introduced as a species and one first introduced as a subspecies are considered synonyms and both were published simultaneously, the species name has priority (Article 24.1). However, this rule has not been consistently followed in mammals. There are 13 currently recognized mammal species that were originally named as subspecies or varieties, but that have a simultaneously published synonym that was originally proposed as a species. I propose to rename 5 recently recognized species that fall in this group: Microdipodops oregonus to M. californicus; Arvicola italicus to A. destructor; Phyllotis stenops to P. tamborum; Peromyscus totontepecus to P. tehuantepecus; and Peromyscus zamorae to P. xenurus. The remaining species should maintain their current names pending action by the International Commission for Zoological Nomenclature. Determining the correct name of mammal species first named as subspecies.
The degradation and fragmentation of native grassland and sagebrush steppe in the western United States have caused population declines and range contractions for several sagebrush steppe associated species including black-tailed jackrabbits (Lepus californicus) and white-tailed jackrabbits (L. townsendii). Conserving these species requires developing effective methods to monitor populations and inform management practices. We evaluated the effectiveness of unbaited camera surveys, baited camera surveys, and fecal pellet surveys at detecting the presence and confirming species identification of black-tailed and white-tailed jackrabbits in 2 study areas in central Washington from September 2022 to June 2023. We also examined the effects of bait and season on detection and identification, and the cost and effort to conduct each method. Unbaited camera and pellet surveys were generally equally effective at detecting and distinguishing jackrabbit species, with unbaited camera detection probabilities ranging from 0.07 to 0.40 and pellet surveys from 0.02 to 0.36. Bait increased species identification rates and detection probabilities for camera surveys, with probabilities ranging from 0.20 to 0.57. Baited cameras had an equal or higher species identification rate and probability of detection compared to unbaited camera and pellet surveys across all analyses. Seasonal conditions, especially snowfall, influenced detection probability for pellet surveys but not unbaited or baited camera surveys. Camera surveys required less time to conduct than pellet surveys, but total cost of camera surveys was much higher than pellet surveys because of the initial investment in cameras and supplies. The cost per jackrabbit detection was similar between pellet and camera surveys; however, the cost per detection of a baited camera was lower than the cost per detection for an unbaited camera. Thus, the best method to choose for monitoring jackrabbits depends on regional weather patterns and the resources available (e.g., eDNA lab, camera equipment, labor). Our research provides the foundation for future studies to monitor jackrabbit populations and evaluate their conservation status throughout their range to better conserve jackrabbits and the ecosystems that depend on them. Unbaited camera and fecal pellet surveys were equally effective at detecting and identifying jackrabbit species across locations, species, and seasons, but several factors had the potential to influence the effectiveness of each method. Most notably, bait significantly increased detection effectiveness of camera surveys.
The Peromyscus difficilis species group inhabits mountainous regions in western North America from Colorado, United States, to Oaxaca, Mexico. Previous work generated a robust phylogeny in which 8 monophyletic lineages representing putative species were identified. This phylogeny coincided only partially with previous systematic arrangements. Based on phylogenetic, geographic, environmental, morphometric, and external traits, and karyotypic attributes, we reassessed the taxonomy and nomenclature of the group. Because cranial and external characteristics were strongly correlated with local environmental attributes not necessarily related to phylogeny, considerable within- and among-lineage variation was detected. Yet, the definition of taxonomic units was possible using the genetic species concept and the complete suite of attributes. Six species were recognized, 2 new to science: P. nasutus, distributed on mountainous areas from Colorado, New Mexico, eastern Arizona, and western Oklahoma to the Rio Grande; Peromyscus sp. nov. 1. from central Sierra Madre Occidental (SMOc); P. sp. nov. 2 from eastern Durango and Coahuila; P. difficilis from the southern portion of the SMOc, Mexican Plateau, and northern Sierra Madre Oriental (SMOr); P. amplus from northwestern Oaxaca, southern SMOr, and central Mexico; and P. felipensis with disjunct populations, 1 from Oaxaca, and 1 from Morelos and southern Mexico City valley. A taxonomic hypothesis for the group based on mitochondrial genetic information, and further testing of this hypothesis using additional nuclear genetic markers, will allow for further exploration of the genetic or epigenetic processes that result in the observed, environmentally mediated phenotypic patterns. Deermice are common and widespread across North America. Exploration of the most remote mountain populations and reassessment of museum samples still allow for discovery of new species. El complejo de especies Peromyscus difficilis habita zonas monta & ntilde;osas del oeste de Norte Am & eacute;rica, desde Colorado, EEUU, hasta Oaxaca, M & eacute;xico. An & aacute;lisis previos generaron una filogenia robusta en la que se identificaron 8 linajes monofil & eacute;ticos o especies gen & eacute;ticas putativas, aunque este arreglo coincide solo parcialmente con la sistem & aacute;tica previa. Con base en evidencia filogen & eacute;tica, geogr & aacute;fica, ambiental, morfom & eacute;trica, morfolog & iacute;a externa y cariotipos, se reevalu & oacute; la taxonom & iacute;a y nomenclatura del grupo. Como las caracter & iacute;sticas externas y craneales estuvieron correlacionadas con atributos ambientales locales no necesariamente ligados al patr & oacute;n filogen & eacute;tico, se observ & oacute; una gran variaci & oacute;n dentro y entre linajes. No obstante, la definici & oacute;n de unidades taxon & oacute;micas fue posible utilizando el concepto gen & eacute;tico de especies y el conjunto de caracteres completo. Se reconocen 6 especies, dos de ellas nuevas para la ciencia: P. nasutus de los EEUU, desde la cuenca del R & iacute;o Bravo, Nuevo Mexico, este de Arizona y hasta Colorado; Peromyscus sp. nov. 1, del centro de la Sierra Madre Occidental (SMOc); P. sp. nov. 2, del este de Durango y Coahuila; P. difficilis, del sur de la SMOc, Altiplano Mexicano y norte de la Sierra Madre Oriental (SMOr); P. amplus, en NW Oaxaca, S SMOr y el centro de M & eacute;xico; y P. felipensis, con dos poblaciones disyuntas en Oaxaca y Morelos y sur del valle de M & eacute;xico. La hip & oacute;tesis taxon & oacute;mica propuesta con base en datos mitocondriales, y su posterior evaluaci & oacute;n usando marcadores gen & eacute;ticos nucleares, permitir & aacute; una exploraci & oacute;n de los posibles procesos gen & eacute;ticos o epigen & eacute;ticos que producen los patrones observados de variaci & oacute;n fenot & iacute;pica asociados con caracter & iacute;sticas ambientales.
Knowledge of growth patterns and physical properties of animals helps researchers assess population characteristics and health in the field. Information on age-specific body measurements and growth patterns is rare in ungulates because examining a large portion of a population is time-, budget-, and personnel-intensive in the wild. We collected age- and sex-specific body measurements from 442 Plains Zebra (Equus quagga boehmi) culled in the Serengeti region, Tanzania, between 1969 and 1971. The dataset contained 307 males and 133 females. We found that males were on average 2.8% larger than females in body measurements of heart girth, height at shoulder, neck-body length, hind foot length, and the body mass, indicating minimal sexual dimorphism in adult Plains Zebra. We used polynomial regression to explore the relationship between heart girth and body mass and applied third-degree polynomial regression models to predict body mass for 34 females and 115 males with recorded girth but missing body mass records. We applied 5 non-linear models-Gompertz, von Bertalanffy, Bertalanffy-Pütter, logistic, and Richards-to characterize sex-specific growth trajectories for each trait. Our results showed that different traits followed different growth patterns, with size asymptotes reached by ∼2 to 5 yr depending on trait and sex. Seasonal trends in adult body mass were also evaluated using generalized linear models incorporating sex and cyclical effects of day of year. While female body mass showed little seasonal variation, adult males exhibited a 16.9% increase in mass during the wet season, followed by a sharp decline, suggesting greater seasonal plasticity and energetic investment. Our work is one of the few studies on body size and growth in wild equids, which provides new information on age- and sex-specific growth trajectories for comparison across zebra subspecies over time and space.
Many mammalian species have been experiencing widespread range expansions, accelerated by various environmental changes in the Anthropocene. These expansions serve as natural experiments, showcasing how organisms adapt and persist while navigating a mosaic of environmental conditions, and they also reveal the dynamic processes that drive species to push their boundaries and thrive in the face of new ecological challenges. The objective of this study was to explore genetic structure of the rapidly expanding Mexican Long-nosed Armadillo (Dasypus mexicanus) in the United States. We collected tissue samples and used the double-digest restriction-site associated DNA sequencing (ddRADseq) approach to generate 14,322 SNPs from 80 individuals, mapped to the Mexican Long-nosed Armadillo genome. We performed phylogeographic analyses and genomic scans for selection to describe genetic signals of the range expansion. We hypothesized that D. mexicanus-a highly mobile, generalist mammal with a broad colonization front would deviate from the typical genetic patterns expected in species undergoing a range expansion. Indeed, our findings revealed no geographic structure, high levels of admixture across United States, and high levels of heterozygosity. We detected numerous loci showing a signal of selection, indicating that the range expansion into colder climates may be facilitated by local adaptation. Our research enhances our understanding of the mechanisms underlying range expansion that are likely typical for medium-sized mammals, and evolutionary dynamics during colonization into new and heterogeneous environments. The Mexican Long-nosed Armadillo, a species of neotropical origin, has in recent years rapidly expanded across the eastern United States. This study examines the genetic structure of the armadillo within the United States and explores the mechanisms driving its rapid expansion and persistence despite encountering novel environmental conditions. The findings highlight the remarkable adaptability and environmental tolerance of the species. Durante el Antropoceno, y como resultado de diversos cambios clim & aacute;ticos, numerosas especies de mam & iacute;feros han experimentado expansiones de su rango. Estas expansiones ofrecen oportunidades & uacute;nicas para caracterizar y estudiar c & oacute;mo los organismos se adaptan y persisten al enfrentar una variedad de condiciones ambientales. As & iacute;mismo, las expansiones revelan los procesos din & aacute;micos que impulsan a las especies a superar sus l & iacute;mites y prosperar frente a nuevos desaf & iacute;os ecol & oacute;gicos. El objetivo de este estudio es el caracterizar la estructura gen & eacute;tica del armadillo mexicano de nueve bandas (Dasypus mexicanus) en los Estados Unidos de Am & eacute;rica. Seleccionamos muestras de tejido de 92 individuos y utilizamos la t & eacute;cnica de secuenciaci & oacute;n de ADN asociada a sitios de restricci & oacute;n mediante digesti & oacute;n doble (ddRADseq) para generar 14,322 SNPs mapeados contra el genoma de esta especie. Realizamos an & aacute;lisis filogeogr & aacute;ficos y de gen & eacute;tica poblacional, as & iacute; como an & aacute;lisis gen & oacute;micos para detectar se & ntilde;ales de selecci & oacute;n, con el fin de describir las se & ntilde;ales asociadas con la expansi & oacute;n de rango. Hipotetizamos que el armadillo mexicano de nueve bandas, un mam & iacute;fero altamente m & oacute;vil y generalista con un frente de colonizaci & oacute;n amplio, se desviar & iacute;a de los patrones gen & eacute;ticos t & iacute;picos predichos para especies en plena expansi & oacute;n de rango. Nuestros hallazgos revelaron una ausencia de estructura geogr & aacute;fica, altos niveles de mezcla gen & eacute;tica a lo largo de su distribuci & oacute;n en los Estados Unidos (USA) y niveles de heterocigosidad elevados. Detectamos numerosos loci que muestran se & ntilde;ales de selecci & oacute;n, lo que indica que la expansi & oacute;n hacia climas m & aacute;s fr & iacute;os podr & iacute;a estar facilitada por adaptaciones locales. Nuestra investigaci & oacute;n profundiza la comprensi & oacute;n de los mecanismos subyacentes a la expansi & oacute;n de rango as & iacute; como la din & aacute;mica evolutiva durante la colonizaci & oacute;n en nuevos ambientes heterog & eacute;neos; los patrones y tendencias podr & iacute;an ser comunes en mam & iacute;feros de tama & ntilde;o medio.
