Understanding predator guild resource use is vital for carnivore species preservation and ecosystem function in high-altitude landscapes. We describe the dietary composition, similarity, and niche overlap for seven carnivore species across three regions of the Qinghai–Tibetan Plateau (Qilian Shan, East Burhanbuda Mountain, Yushu) using DNA metabarcoding of 760 scat samples. Analyses found 33 unique prey items representative of the classes Mammalia, Aves, and Actinopterygii. Blue sheep (Pseudois nayaur) and pika (Ochotona sp.) were most frequently detected. Livestock in carnivore diets ranged from 4% to 7% depending on site, but accounted for 21.7% of Tibetan wolf (Canis lupus) diet. Eurasian lynx (Lynx lynx), Tibetan fox (Vulpes ferrilata), Pallas's cat (Otocolobus manul), and snow leopard (Panthera uncia) had highly uneven diets. Intraguild predation of mesocarnivores by apex carnivores was found. Analysis of dietary niche overlap using Pianka's index showed that overlap was significantly greater than expected among all carnivores examined and between apex and mesocarnivores, though significant correlations between carnivore body mass and prey body mass suggested broad separation in consumed prey. Snow leopard and Tibetan wolf diets were consistently the most similar of any two given species pairs. This study provides evidence of high dietary overlap. Protection for species consumed by a wide variety of carnivores will benefit predator guilds in the area and assist in maintaining the relatively low frequency of livestock predation. This work provides insight into the dynamics of carnivore guilds living in an area that has worldwide impacts, and methods herein could be applied on global scales for conservation efforts.

Direct and indirect interactions among predators affect predator fitness, distribution, and overall community structure. Yet, outside of experimental settings, such interactions are difficult to observe and thus poorly understood. Patterns of niche overlap among predators reflect and shape community interactions and may therefore help elucidate the nature and intensity of intraguild interactions. To better understand the coexistence of two apex predators, snow leopards (Panthera uncia) and wolves (Canis lupus), we investigated their spatial, temporal, and dietary niche overlap in summer in the Pamir Mountains of Tajikistan. We estimated population-level space use via spatial capture–recapture models based on noninvasive genetics and camera traps, diel activity patterns based on camera trap detections, and diet composition from prey remains in carnivore scats, from which we estimated coefficients between 0 and 1 for overlap in space, time, and diet, respectively. Snow leopards and wolves displayed moderate spatial partitioning (0.26, 95% confidence interval [CI]: 0.17–37), but overlapping temporal (0.77, 95% CI: 0.64–0.90) and dietary (0.97, 95% CI: 0.80–0.99) niches. Both predators relied on seasonally abundant marmots (Marmota caudata) rather than wild ungulates, their typical primary prey, suggesting that despite patterns of overlap that were superficially conducive to exploitation competition and predator facilitation, prey were likely not a limiting factor. Therefore, prey-mediated interactions, if present, were unlikely to be a major structuring force in the ecosystem. By implication, carnivore conservation planning and monitoring in the mountains of Central Asia should more fully account for the seasonal importance of marmots in the ecosystem.

Temporal niche partitioning between ecologically similar species may decrease interspecific competition and facilitate their coexistence, but the temporal interactions between sympatric skunks are still poorly understood. Furthermore, different interacting factors to explain activity patterns and their role in species coexistence in the temporal niche have been overlooked. Using camera traps over 2 years, we evaluated the temporal segregation between Conepatus leuconotus and Spilogale pygmaea and the influence of biotic, abiotic, and anthropogenic factors in shaping their daily and monthly activity patterns in a seasonal tropical forest at the Mexican Pacific slope. Both skunks selected the nocturnal and crepuscular periods, with strong avoidance of daylight hours. We observed partial temporal segregation between species without significant seasonal variation. Spilogale pygmaea was most active when the activity of C. leuconotus decreased, suggesting that S. pygmaea adopts a temporal avoidance strategy to decrease the potential for direct encounters with the dominant species. We found that skunk activity patterns are also determined by the activity of prey and native and exotic predators, as well as relative humidity, precipitation, cloud cover, and night length. Our results showed that these factors differently affect daily and monthly activity between seasons and their effect varies in each species. This study provides evidence that multiple extrinsic factors play an important role in shaping the daily and monthly activity patterns of both skunks and, of course, affect their temporal niche partitioning, possibly promoting coexistence in a seasonal tropical environment.

La partición del nicho temporal entre especies ecológicamente similares puede disminuir su competencia interespecífica y facilitar su coexistencia, pero las interacciones temporales entre zorrillos simpátricos todavía siguen siendo poco conocidas. Además, se ha pasado por alto la interacción de diferentes factores para explicar los patrones de actividad y su papel en la coexistencia de las especies en el nicho temporal. Utilizando cámaras trampa durante dos años, evaluamos la segregación temporal entre Conepatus leuconotus y Spilogale pygmaea y la influencia de factores bióticos, abióticos y antropogénicos en la configuración de sus patrones de actividad diaria y mensual en un bosque tropical estacional en la vertiente del Pacífico mexicano. Ambos zorrillos seleccionaron el período nocturno y crepuscular, evitando fuertemente las horas del día. Observamos una segregación temporal parcial entre especies sin una variación estacional significativa. S. pygmaea estuvo más activa cuando la actividad de C. leuconotus disminuía, sugiriendo que S. pygmaea adopta un evitación temporal para disminuir el potencial de encuentros directos con la especie dominante. Encontramos que los patrones de actividad de los zorrillos también están influenciados por la actividad de las presas y de depredadores nativos y exóticos, así como la humedad relativa, precipitación, nubosidad y duración de la noche. Nuestros resultados mostraron que estos factores afectaron de manera diferente la actividad diaria y mensual entre estaciones y su efecto varió en cada especie. Este estudio proporciona evidencia de que múltiples factores extrínsecos juegan un papel importante en la configuración de los patrones de actividad diaria y mensual de ambos zorrillos y desde luego, afectan la partición de sus nicho temporales, promoviendo posiblemente la coexistencia en un ambiente tropical estacional.

Agricultural intensification has caused population declines and reduced species diversity in both arthropods and their predators. Despite conservation and habitat management implications, the effects of land-use change on the trophic relationships between nocturnal arthropod predators and their prey have seldom been described. To assess how arthropodivorous bats may have shifted their diets in response to land-use changes, we compared bulk δ¹³C and δ¹⁵N values from little brown and big brown bat museum specimens and carcasses collected in the Upper Midwestern region of the United States from 1898 to 2019. As an exploratory analysis, we also investigated relationships between isotopic values and climate or landcover variables to quantify potential correlations with changes in arthropodivorous bat foraging patterns over time. Overall, we found that isotopic niche overlap of little brown and big brown bats increased from 24% to 45% between historical and contemporary time periods. Our results indicate that the isotopic niches of little brown bats have been largely conserved, whereas the isotopic niches of big brown bats are more flexible and became more similar to little brown bats over time. Further analyses showed that stable isotope values from arthropodivorous bat tissues were also correlated with certain landcover variables such as the prevalence of wetland, forest, and grassland habitats, but not with the prevalence of agricultural land on a local scale. These findings suggest that the foraging patterns of some aerial arthropodivores have shifted in response to the loss of habitat diversity and corresponding changes in prey resources.

La intensificación de la agricultura ha generado una disminución de las poblaciones y una reducción de la diversidad de especies de ambos artrópodos y sus depredadores. A pesar de las implicaciones para la conservación y el manejo del hábitat, raras veces se han descrito los efectos del cambio de uso de la tierra sobre las relaciones tróficas entre los depredadores nocturnos de artrópodos y sus presas. Para evaluar cómo los murciélagos artropodívoros pueden haber modificado sus dietas en respuesta a los cambios en el uso de la tierra, comparamos los valores de δ¹³C y δ¹⁵N de especímenes de museo e individuos hallados muertos de miotis norteamericano (Myotis lucifugus) y murciélago moreno norteamericano (Eptesicus fuscus), recolectados en la región del Upper Midwest de los Estados Unidos en el período 1898-2019. A través de un análisis exploratorio, también investigamos las relaciones entre los valores isotópicos y las variables climáticas o de cobertura del suelo para cuantificar las potenciales correlaciones con los cambios en los patrones de alimentación de los murciélagos artropodívoros a lo largo del tiempo. En general, encontramos que la superposición entre los nichos isotópicos de miotis norteamericano y murciélago moreno norteamericano aumentó del 24% al 45% entre los períodos histórico y contemporáneo. Nuestros resultados indican que los nichos isotópicos del miotis norteamericano han sido ampliamente conservados, mientras que los nichos isotópicos del murciélago moreno norteamericano son más flexibles y se volvieron en el tiempo más similares a los del miotis norteamericano. Análisis adicionales mostraron que los valores de los isótopos estables en los tejidos de los murciélagos artropodívoros estaban correlacionados también con ciertas variables de cobertura del suelo como la prevalencia de hábitats de humedales, bosques y pastizales, mientras no resultaban correlacionados con la prevalencia de cultivos a escala local. Estos resultados sugieren que los patrones de alimentación contemporáneos de algunos artrópodívoros aéreos han cambiado en respuesta a la pérdida de diversidad de hábitat y los cambios correspondientes en la disponibilidad de recursos para las presas.

Species distribution and persistence have long been known to vary with landscape structure; however, continued human activities in altered landscapes raise many questions as to how habitat fragmentation impacts the biology of persistent animal populations. Using carbon and nitrogen stable isotope analysis, we examined interspecific variation in the diet of frugivorous bats among remnant habitat patches of Brazil's Atlantic Forest. We hypothesized that the diet of individuals captured in habitat patches would be different than those captured in contiguous habitats. We predicted that bats would alter their realized dietary niche breadth, taking food items (i.e., fruits or insects) according to landscape structure. However, more mobile species should be less impacted by small-scale landscape changes. We predicted that (1) a wide-ranging species (Artibeus lituratus), which move through open areas, will be less affected by small-scale landscape attributes, patch size, composition, and isolation; while (2) two narrow-ranging species (Carollia perspicillata and Sturnira lilium) will have more variation between populations in niche breadth and isotopic ratio ranges dependant on the local environment. Using Akaike's Information Criterion (AIC) to rank a priori selected candidate models to explain variation, we found that fragment composition, largely involving vegetation density rather than spatial aspects of landscape structure (i.e., patch area, isolation) best explained diet variation in frugivorous bats. Additionally, there was evidence that wide-ranging A. lituratus were less impacted by differences in the landscape than narrow-ranging species. This supports the prediction that bats resident to fragments have altered feeding behavior, in response to environmental perturbation.

A distribuição e persistência de espécies variam de acordo com a estrutura da paisagem. Entretanto, atividades humanas contínuas em paisagens alteradas levantam muitas perguntas sobre como a fragmentação do habitat pode impactar a persistência de populações animais. Utilizando uma análise de isótopos estáveis de carbono e nitrogênio, examinamos a variação interespecífica na dieta de morcegos frugívoros em um mosaico de remanescentes de Mata Atlântica. Nossa hipótese é que a dieta de indivíduos capturados em fragmentos florestais é diferente da dieta dos morcegos capturados em ambientes de floresta contínua. Prevemos que os morcegos irão alterar a amplitude do seu nicho alimentar, utilizando diferentes recursos (i.e., frutos ou insetos), de acordo com a estrutura da paisagem. Porém, as espécies mais móveis serão menos impactadas por mudanças na paisagem de pequena escala. Prevemos que (1) espécies móveis (Artibeus lituratus), que se movem através de áreas abertas, serão menos impactada por características da paisagem de pequena escala, tamanho, composição e isolamento do fragmento, enquanto (2) espécies menos móveis (Carollia perspicillata e Sturnira lilium) apresentarão maior variação entre a amplitude de nicho e taxas de isótopos, dependendo do ambiente local. Utilizando o Critério de Informação de Akaike (AIC) para avaliar modelos explicativos, concluímos que a composição do fragmento, principalmente envolvendo a densidade da vegetação ao invés de aspectos espaciais da estrutura da paisagem (i.e., tamanho dos fragmentos, isolação) explica melhor a variação na dieta de morcegos frugívoros. Além disso, há evidencias que Artibeus lituratus, uma espécie de maior mobilidade, foi menos impactado pelas diferenças na paisagem que as espécies menos móveis. Esses resultados sustentam as previsões de que morcegos residentes em fragmentos modificaram seus comportamentos alimentares em resposta a perturbação ambiental.

Species can coexist spatially and temporally by partitioning the niche space and forming complex assemblages made up of different species that share the prey resource. Chiroptera is the second most species-rich mammalian order and about 75% of bat species feed on arthropods, which makes these bats a good model group for studying complex trophic interactions. Next-generation parallel sequencing techniques allow a detailed analysis of arthropod resource partitioning patterns in bats. However, previous studies have not reached a consensus on the concordance between diet composition, habitat use, and segregation of trophic resources in bats. We analyzed diet composition in terms of taxonomy of the insect prey, and the prey characteristics. Feces of 16 bat species were examined in the Mexican Neotropics. We carried out a SIMPER (similarity percentage) test, nonmetric multidimensional scaling, and principal component analyses to identify general segregation patterns of trophic resources in relation to the habitat-use guild of bats and computed Pianka's niche overlap index between species and Levin's index to estimate the niche width of each species. Bats from the same locality tend to partition their diet, with a niche overlap ranging between 0.5 and 0.8. The highest values were found between species with different foraging behaviors. We suggest that future bat diet studies should incorporate the ecological and taxonomic information of arthropod prey to better understand the trophic interactions with bats.

Aproximadamente el 75% de las especies de murciélagos se alimentan de artrópodos, algunas de estas especies pueden coexistir espacial y temporalmente al particionar el espacio del nicho. Los murciélagos forman ensamblajes complejos compuestos por diferentes especies que comparten su recurso trófico. Por tanto, los murciélagos pueden utilizarse como grupo modelo para estudiar interacciones tróficas complejas. Las técnicas de secuenciación masiva paralela del ADN permiten un análisis detallado de sus patrones de partición de recursos tróficos. Sin embargo, los estudios no han llegado a un consenso sobre la concordancia entre la composición de la dieta, el uso del hábitat y la partición de los recursos tróficos en los murciélagos. Analizamos la composición de la dieta en términos de taxonomía de los artrópodos presa y sus características ecológicas. Examinamos las heces de 16 especies de murciélagos a lo largo del Neotrópico Mexicano. Se utilizaron análisis de similitud porcentual (SIMPER), escalamiento multidimensional no métrico y análisis de componentes principales para identificar patrones generales de partición de recursos tróficos en relación con el gremio de uso de hábitat de los murciélagos. Calculamos el índice de superposición de nicho de Pianka entre especies y el índice de Levin para estimar la amplitud del nicho de cada especie. Encontramos que los murciélagos de la misma localidad tienden a diferenciar su dieta, con una superposición de nicho que varía entre 0.5 y 0.8. Los valores más altos se encontraron entre especies con diferentes hábitos de alimentación. Sugerimos que, en el futuro, los estudios de dieta de murciélagos consideren las características ecológicas de sus presas y utilicen la información taxonómica como clave para recuperar información sobre la biología de las presas y comprender la ecología de estas interacciones tróficas.

The Order Chiroptera comprises more than 1,400 species, each with its evolutionary history and under unique selective pressures, among which are the host–pathogen interactions. Bats have coped with complex interactions with a broad spectrum of microbes throughout their evolutionary history, prompting the development of unique adaptations that allow them to co-exist with microbes with pathogenic potential more efficiently than other nonadapted species. In this sense, an extraordinary immune system with unique adaptations has been hypothesized in bats. To explore this, we focused on the major histocompatibility complex (MHC), which plays a crucial role in pathogen recognition and presentation to T cells to trigger the adaptive immune response. We analyzed MHC class I transcripts in five species, each from different families of New World bats. From RNA-seq data, we assembled a partial region of the MHC-I comprising the α1 and α2 domains, which are responsible for peptide binding and recognition. We described five putative functional variants, two of which have two independent insertions at the α2 domain. Our results suggest that this insertion appeared after the divergence of the order Chiroptera and may have an adaptive function in the defense against intracellular pathogens, providing evidence of positive selection and trans-specific polymorphism on the peptide-binding sites.

El orden Chiroptera comprende más de 1400 especies, cada una con su propia historia evolutiva y sometida a distintas presiones selectivas, entre las cuales se encuentran las interacciones huésped-patógeno. Los murciélagos han sobrellevado interacciones complejas con un amplio espectro de microorganismos a lo largo de su historia evolutiva, lo que ha permitido el desarrollo de adaptaciones únicas que les permiten coexistir con microorganismos con potencial patogénico, con mayor eficacia que otras especies no adaptadas. Es por esto que se ha desarrollado la hipótesis de que los murciélagos tienen un sistema inmunológico extraordinario con adaptaciones únicas. Para explorar esto, nosotros nos enfocamos en el Complejo Mayor de Histocompatibilidad (MHC), que juega un papel crucial en el reconocimiento y presentación de patógenos a las células T para desencadenar la respuesta de inmunidad adaptativa. Analizamos los transcriptos del MHC de clase I en cinco especies de murciélagos del Nuevo Mundo, cada una de diferentes familias. A partir de los datos de RNA-seq, describimos los dominios α1 y α2, que son responsables del reconocimiento y unión de péptidos. Describimos cinco posibles variantes funcionales, dos de las cuales tienen dos inserciones independientes en el dominio α2. Nuestros resultados sugieren que esta inserción apareció después de la divergencia del orden Chiroptera y puede tener una función adaptativa en la defensa contra patógenos intracelulares, proveyendo evidencia de selección positiva y polimorfismo transespecífico en los sitios de unión a péptidos.

Bats are among the most valuable pollinators of economically important crops in Mexico including agaves and columnar cacti. High demand for the agricultural products of these crops has resulted in increasing use of agrochemicals, including pesticides and fertilizers, to increase yield and decrease pest damage. However, these compounds can negatively affect crop mutualists such as pollinating bats. In this study, we investigated: (i) how the application of the broad-spectrum pesticide carbamate and/or synthetic fertilizers affect crop yield of the pitaya cacti (Stenocereus queretaroensis); (ii) whether carbamate bioaccumulates in pitaya nectar and fruits; and (iii) whether the application of these agrochemicals affects visitation rates of the pitaya's most efficient pollinators, nectarivorous bats of the genus Leptonycteris. We designed an experiment consisting of four treatments (pesticide, nutrients, both, or neither) applied to pitaya plants. We estimated the effect of each treatment by quantifying pitaya reproductive structures (flower buds and flowers) and fruit yield and quality, performed trace analysis to detect the pesticide in the nectar and fruits, and estimated bat flower visitation rates using camera traps to determine whether the addition of agrochemicals influenced pitaya–bat interactions. We found that none of the treatments increased yield or fruit sweetness, and they did not affect bat visitation rates. Fruit pulp and floral nectar contained pesticide concentrations above those permitted by international environmental agencies. Thus, our results show that adding these agrochemicals to pitaya crops does not improve yield but could negatively affect their crop pollinators, especially since bats apparently do not avoid visiting flowers containing pesticide residues.

Los murciélagos están entre los polinizadores más valiosos de cultivos económicamente importantes en regiones megadiversas, como los agaves y los cactus columnares en México. Sin embargo, la alta demanda de productos agrícolas ha resultado en un aumento en el uso de agroquímicos para mantener altos rendimientos y cultivos libres de plagas. Estos compuestos (i.e., pesticidas y fertilizantes) pueden afectar negativamente a los mutualistas de los cultivos, como los murciélagos polinizadores. En este estudio, investigamos (i) cómo la aplicación del plaguicida de amplio espectro carbamato y/o fertilizantes sintéticos afecta el rendimiento del cultivo de pitaya (Stenocereus queretaroensis); (ii) si el carbamato se bioacumula en el néctar y las frutas de pitaya; y (iii) si la aplicación de estos agroquímicos afecta las tasas de visita de los polinizadores más eficientes de la pitaya, los murciélagos nectarívoros del género Leptonycteris. Diseñamos un experimento que consistió en cuatro tratamientos (pesticida, nutrientes, ambos, ninguno) aplicados a las plantas de pitaya. Estimamos el efecto del tratamiento sobre el rendimiento del cultivo midiendo las estructuras reproductivas de la pitaya (botones y flores), el número de frutos producidos, y la concentración de sacarosa de los frutos. Realizamos un análisis de trazas de plaguicidas en el néctar y los frutos recolectados de los tratamientos para determinar la bioacumulación de plaguicidas. Para determinar si la adición de pesticidas a la planta influyó en la interacción con los murciélagos, estimamos (por cada tratamiento) la tasa de visitas de murciélagos a las flores utilizando cámaras trampa. Encontramos que ninguno de los tratamientos aumentó el rendimiento del cultivo y tampoco afectaron la tasa de visitas de los murciélagos. Se registraron trazas de pesticidas tanto en la pulpa de la fruta como en el néctar floral, en concentraciones superiores a las permitidas por las agencias ambientales internacionales. Nuestros resultados muestran que la adición de agroquímicos a los cultivos de cactus no mejora el rendimiento, pero sí podría afectar a los polinizadores de los cultivos, ya que es posible que los murciélagos no logren discriminar las flores que contienen trazas químicas.

Effective conservation and management of a species relies upon understanding its habitat throughout its full annual cycle. For hoary bats, Lasiurus cinereus, their ecology is largely known from summer with the exception that they move long distances during autumn and spring and maintain some level of activity year-round. Autumn is a critically important period for hoary bats as they complete long-distance migrations between summer and winter range and they mate, both of which are energetically expensive. We studied hoary bat roost selection during autumn in a migratory stopover area in redwood habitat in northwestern California. We hypothesized that hoary bats select day roosts during autumn migration that minimize energetic expenditures and improve mating opportunities. We located 24 day roost sites of male hoary bats and evaluated site-level roost selection by comparing roosts with 120 random locations. We used multiple logistic regression to compare remotely sensed habitat features derived from LiDAR and other spatial data. The three most important variables for distinguishing roost from random locations were distance to creek, roads, and meadow. We speculate that selection of roosts in proximity to open spaces and flyways facilitated social behaviors related to mating that are commonly observed in this area.

La conservación y manejo de una especie se basan en el conocimiento de su hábitat a lo largo de todo su ciclo de vida anual. La ecología del murciélago cenizo, Lasiurus cinereus, es ampliamente conocida para la época de verano, además que se desplaza grandes distancias durante el otoño y la primavera, con algún grado de actividad durante todo el año. El otoño es una época crítica para la especie al completar su migración entre las áreas de verano e invierno, y además de aparearse, ambos eventos con un alto costo energético. Estudiamos la selección de refugios del murciélago cenizo durante el otoño en un área de parada migratoria en los bosques de secuoyas, en el noroeste de California. Nuestra hipótesis proponía que esta especie, durante su migración de otoño, elige refugios temporales que permiten minimizar su gasto energético y mejorar sus probabilidades de apareamiento. Ubicamos 24 refugios de descanso diario, y evaluamos la selección de sitios de refugio comparando con 120 localidades al azar. Utilizamos regresión logística múltiple para comparar características del hábitat detectadas a través de sensores remotos registrados mediante LiDAR, y otros datos espaciales. Las tres variables más importantes para distinguir los refugios de las localidades elegidas al azar fueron, distancia a arroyos, caminos y praderas. Deducimos que la selección de refugios en cercanía a espacios abiertos y rutas migratorias facilitan comportamientos sociales relacionados con el apareamiento, algo que es fácil de observar en el área.

Black-tailed prairie dogs (Cynomys ludovicianus) exhibit boom and bust cycles in landscapes where they are affected by outbreaks of plague caused by the introduced bacterium Yersinia pestis. We examined spatiotemporal dynamics of black-tailed prairie dog colonies in the Thunder Basin National Grassland, Wyoming over a period of 21 years. The colony complex experienced three plague epizootics during that time, and consequently three boom and bust cycles. The entire prairie dog colony complex collapsed over a 1-year period during the first and third epizootics, and over a 3-year period during the second epizootic. The boom and bust cycles were characterized by relatively rapid contractions in total area occupied by prairie dogs during a plague outbreak (e.g., >99% decline from 10,604 ha to 47 ha over 1 year [2017–2018]) followed by much slower recovery times (e.g., an increase from 410 ha to 10,604 ha over 11 years [2006–2017]). Prairie dogs occupied a total of 10,604 ha during at least one survey within the study period, but much of the area was not continuously occupied over time. We found that each of the three plague outbreaks occurred in years with highly connected prairie dog colonies and slightly above-average temperatures and summer precipitation, which were preceded by a dry year. Although plague outbreaks were associated with climatic conditions, we were unable to detect a role of climate in driving colony expansion. Our results illustrate the cyclic and extreme nature of fluctuations in black-tailed prairie dog colony size and distribution in a landscape where plague occurs and illuminate some of the drivers of these cycles. Further, our work shows how introduced diseases can dramatically influence populations of a keystone species, with important consequences for the broader ecological system.

Understanding the relative importance of exogenous and endogenous factors in natural population dynamics has been a central question in ecology. However, until recently few studies used long-term data to assess factors driving small mammal abundance in Neotropical savannas. We used a 9-year data set, based on monthly captures, to understand the population dynamics of two scansorial small mammals inhabiting the Brazilian Cerrado: the semelparous gracile mouse opossum (Gracilinanus agilis), and the iteroparous long-tailed climbing mouse (Rhipidomys macrurus), the two most abundant species at Panga Ecological Station (Uberlândia/MG). We tested the impact of two fires that occurred in 2014 and 2017 on the abundance of both populations. Also, we used Royama's framework to identify the role of the endogenous system (intraspecific competition) and exogenous factors (annual rainfall, days with minimum and maximum temperatures, annual minimum Normalized Difference Vegetation Index [NDVI], and Southern Oscillation Index) in population dynamics. Extensive and severe fires had a lasting, negative impact on the studied populations, probably by reducing the carrying capacity of the environment. Both populations were influenced by negative first-order feedback, indicating density-dependent effects. Moreover, the endogenous system and the annual minimum NDVI operated as vertical effects determining G. agilis dynamics, while the R. macrurus population was governed by the vertical effects of 1-year lagged rainfall. Our results support the contention that small mammal population fluctuations are driven by the interaction between endogenous (density-dependent) and exogenous factors, which in this study were mainly associated with habitat complexity. Despite ecological similarities shared by both species, their response and recovery time to disturbances and environmental variables varied, probably due to their contrasting life histories. Hence, we emphasize the need to consider species life histories to understand the responses of small mammals to extreme events and reinforce the importance of long-term studies that evaluate the combined effects of endogenous and exogenous variables on population dynamics.

A compreensão da importância relativa de fatores exógenos e endógenos na dinâmica de populações naturais tem sido uma questão central na ecologia. Porém, até o momento, poucos estudos analisaram os fatores que determinam a abundância de pequenos mamíferos em savanas Neotropicais utilizando dados de longo prazo. Nós usamos um conjunto de dados de 9 anos, baseado em capturas mensais, para investigar a dinâmica de duas espécies escansoriais que habitam o Cerrado Brasileiro: a cuíca graciosa (Gracilinanus agilis) e o rato da árvore (Rhipidomys macrurus). Ambas são muito abundantes na Estação Ecológica do Panga (Uberlândia/MG), sendo a primeira semélpara e a segunda iterópara. Nós testamos o impacto de duas queimadas que ocorreram em 2014 e 2017 sobre a abundância das populações. Utilizamos a abordagem de Royama para identificar o efeito dos fatores endógenos (competição intraespecífica) e exógenos (precipitação anual, número de dias com temperaturas mínimas e máximas, valor mínimo anual do índice Normalizado de Diferença Vegetal - NDVI e Indíce de Oscilação Sul) sobre a dinâmica populacional. Incêndios extensos e severos impactaram negativamente ambas as populações, muito provavelmente pela redução na capacidade de suporte do ambiente. As duas espécies foram influenciadas por uma retroalimentação negativa de primeira ordem, indicando efeito de denso-dependência. Além disso, tanto o sistema endógeno quanto o NDVI (proxy da cobertura vegetal) operaram como um efeito de perturbação vertical gerando flutuações populacionais em G. agilis, enquanto a dinâmica populacional de R. macrurus foi governada pelo efeito vertical da chuva com defasagem de 1 ano. Nossos resultados corroboram a afirmativa de que a dinâmica populacional de pequenos mamíferos é determinada pela interação entre fatores dependentes de densidade e fatores exógenos, os quais estiveram relacionados à cobertura vegetal nesse estudo. Apesar da similaridade ecológica, as espécies apresentaram tempos de resposta e de recuperação às variáveis ambientais distintos, provavelmente em função de suas histórias de vida contrastantes). Assim, reforçamos a necessidade de considerar a história de vida das espécies para entender suas respostas a eventos extremos, e enfatizamos a importância de estudos de longo prazo que investiguem o efeito sinergístico de fatores endógenos e exógenos sobre a dinâmica das populações naturais.

The conservation of threatened species often requires an examination of home range, foraging preferences, and diet. We used radio tracking, global positioning system data loggers, and fecal pellet analyses to study the nocturnal ecology of an endangered desert mammal, the sandhill dunnart, Sminthopsis psammophila. Twenty-four individuals were tracked between 2015 and 2018. The mean home range area of S. psammophila was 70 ha (100% minimum convex polygon). Reproductive males had a mean home range of 148 ha, whereas the ranges of all other groups were comparatively smaller. Sminthopsis psammophila preferred dense, long unburned foraging habitats. There was no effect of weather (excluding extreme cold/rain) on nocturnal ranging behavior. Ants comprised a significant proportion of the diet of S. psammophila and S. hirtipes, whereas S. dolichura consumed a broader range of prey. By integrating foraging and dietary analyses, we provide new insights to improve the conservation management of one of Australia's least studied but most threatened marsupials.

Botflies (Diptera: Cuterebra sp.) are widely distributed and seasonally abundant parasites of small mammals in North America. To assess their effect on rodent survival, we studied the demography of botfly parasitism on small mammals in northeastern Kansas during 1995–1999. Additional comparisons on botflies parasitizing small mammals were made to a nearby old-field grid where mark–recapture studies continued from 1975 to 2003. White-footed mice, Peromyscus leucopus, were infected by botfly larvae (Cuterebra fontinella) each year during our study. The period of infection for P. leucopus was June–December, with the highest proportion of mice infected in July and August. A smaller, second peak of infection in October and November indicated that C. fontinella reproduced bimodally at this latitude with distinct summer and autumn population peaks. During the botfly seasons of the 5 years, 140 (23.3%) of 602 P. leucopus captured were infected. The percentages of individuals infected during 1995, 1996, 1997, and 1999 were not significantly different (22.4%, 17.3%, 17.1%, and 22.7%, respectively). However, in 1998, 32.4% individuals were infected with a higher incidence of multiple infections and a greater number of botfly larvae per host. Nearly half (47%) of the infected individuals caught in 1998 had infections in both summer and autumn, compared with 25% during the 1995–1997 seasons. In 1999, 63% of infected mice had at least a 2nd infection during the autumn. For all 5 years, 82%, 14%, and 4% of the infected mice had one, two, or three botflies, respectively. In 1998, 24% of the infected mice carried two or more botflies at one time, compared to 14% from 1995–1997 and 11% in 1999. Overall 94% of the infected mice were adults, with no differences between sexes. The variation seen in the prevalence of botfly parasitism of white-footed mice correlates to yearly weather fluctuations. Other demographic aspects of the infected mice, such as sex ratio, age, and longevity of those infected, did not change year to year. Our data suggest that infection with Cuterebra has little negative or positive impact upon populations of white-footed mice.

Los tábanos (Diptera; Cuterebra) son un grupo de moscas parásitas con variable abundancia estacional en Norte América. Para determinar su efecto en la supervivencia de roedores estudiamos la demografía del parasitismo por tábanos en mamíferos pequeños del noreste de Kansas desde 1995 hasta 1999. Se realizaron comparaciones adicionales del parasitismo de larvas de tábanos usando una retícula de trampas en una zona aledaña, donde estudios de captura-marcaje-recaptura fueron realizados desde 1975 hasta 2003. El ratón de patas blancas (Peromyscus leucopus) fue parasitado por larvas de tábanos (Cuterebra fontinella) en todos los años de nuestro estudio. El período de infección para P. leucopus fue entre junio y diciembre, con una mayor proporción de ratones infectados entre julio y agosto. Un segundo pico menor de infección sucedió entre octubre y noviembre, indicando que C. fontinella es bimodal en la latitud de nuestro estudio, con picos poblacionales diferenciables en el verano y el otoño. Durante lastemporadas de tábanos de los 5 años, 140 (23.3%) de 602 P. leucopus capturados presentaron infecciones. Los porcentajes de individuos infectados en los años 1995, 1996, 1997 y 1999 no fueron diferentes a nivel estadístico (22.4%, 17.3%, 17.1%, y 22.7%, respectivamente). Sin embargo, en 1998, un 32.4% de los individuos fueron infectados, con una alta incidencia de infecciones múltiples, y un número mayor de larvas de tábano por hospedador. Casi la mitad (47%) de los individuos infectados capturados en 1998 tuvieron infecciones tanto en verano como en otoño, frentea un 25% durante el periodo1995–1997. En 1999, el 63% de los ratones infectados tuvo al menos una segunda infección durante la misma estación. Para todos los años, el 82%, 14% y 4% de los ratones infectados tuvieron 1, 2, o 3 larvas, respectivamente. En 1998, el 24% de los ratones infectados transportaron dos o más larvas al mismo tiempo, comparado con el 14% durante 1995–1997 y el 11% en 1999. En general, el 94% de los ratones infectados fueron adultos y no observamos diferencias en infección entre sexos. La variación observada en la prevalencia de parasitismo estuvo correlacionada con fluctuaciones climáticas anuales. Otros aspectos de la demografía de parasitismo en ratones, por ejemplo, proporción de sexos, edad, longevidad de los individuos infectados, no cambiaron entre años. Nuestros resultados sugieren que la infección por Cuterebra tiene poco impacto negativo o positivo en la población de ratones de patas blancas.

Deviations from a 50:50 sex ratio by producing either more sons or daughters can provide fitness benefits for the parents. This is especially true for species where one sex has skewed reproductive success, in most cases males. The factors responsible for these shifts are not fully understood, but some relationships have been uncovered such as parental age. We looked for a potential relationship between the parental age of meadow voles and offspring sex ratios using a captive population. A trending linear relationship was found with paternal age and a significant quadratic relationship was found with maternal age. For males, older fathers tended to sire more sons compared to younger fathers which may be the result of selective forces of competition because of skewed reproductive success. For females, middle-aged mothers sired more sons compared to younger or older mothers. Middle age for a female could represent an optimal point for producing sons that are able to survive and compete with other males for reproductively available females.

Wildfire is a natural ecosystem disturbance in forests in North America, yet fires are often at odds with human activity and affect the timber supply. Postfire salvage logging is common practice globally, but the impacts of salvage logging on wildlife, especially small mammal communities, remain unclear. We livetrapped small mammals to determine their population responses to wildfire and postfire salvage logging in central British Columbia, Canada. Postfire regenerating forest provided habitat for deer mice (Peromyscus maniculatus), southern red-backed voles (Myodes gapperi), and meadow voles (Microtus pennsylvanicus). Postfire salvage logging significantly reduced tree basal area and changed small mammal community structure by reducing southern red-backed vole populations and supporting mainly deer mice, a generalist species. Given the large scale and intensity of postfire salvage logging operations across the province, salvage logging has the potential to decrease vole populations and change small mammal communities across the province.

Shrub encroachment is altering the structure and species composition of natural communities across the globe. However, little research has focused on how shrub encroachment influences wetland vertebrates, including small mammals. We sought to determine how vegetative structure and shrub cover influenced the occurrence of a threatened semiaquatic mammalian subspecies, the Sanibel Island rice rat (Oryzomys palustris sanibeli). We evaluated the influence of vegetation and metrics of inundation on probability of occurrence and localized seasonal colonization and extinction rates of the Sanibel Island rice rat over a 3-year period. We found Sanibel Island rice rats on 18 (33.3%) of our 54 sites. Their occurrence was positively associated with greater sand cordgrass (Spartina bakeri) cover and increased elevation, but negatively associated with greater shrub cover. Their probability of localized colonization was negatively associated with greater shrub cover. Localized extinction probabilities for Sanibel Island rice rats were positively associated with increased rainfall totals in the preceding 3 months and greater shrub cover. Using aerial photography from across the Sanibel Island rice rat's range, we found 5.5-fold greater shrub cover in 2015 than in 1944. We suggest that increases in shrub cover and reduced cordgrass cover may be driving the decline of this once ubiquitous endemic species and that the encroachment of freshwater wetlands requires greater attention due to its potential to imperil wetland-dependent wildlife.

The use of scent for communication is widespread in mammals, yet the role of scent-marking in the social system of many species is poorly understood. Nilgai antelope (Boselaphus tragocamelus) are native to India, Nepal, and Pakistan. They were introduced to Texas rangelands in the United States during the 1920s to 1940s, and have since expanded into much of coastal South Texas and northern Mexico. The nilgai social system includes the use of latrines or repeated defecation at a localized site. We quantified and described physical and behavioral characteristics of nilgai latrine ecology to investigate drivers of latrine use at three sites in South Texas, during April 2018 to March 2019. Latrines were abundant (2.6–8.7 latrines/ha on unpaved roads, 0.4–0.9 latrines/ha off-roads), with no evidence for selection as to vegetation communities; latrines were dynamic in persistence and visitation rates. We found higher densities of latrines in Spring surveys, just after the peak of nilgai breeding activity, compared to Autumn surveys. Density of nilgai latrines was 3–10 times greater than estimated population densities, indicating individual nilgai must use multiple latrines. Camera traps and fecal DNA analysis revealed latrines were mainly (70%) visited by bulls and defecated on by bulls (92% in photos, 89% for DNA samples). The greatest frequency of visits occurred during the peak in the nilgai breeding season, from December–February; latrines were visited every 2–3 days on average. Body characteristics of photographed individuals and genetic analysis of feces indicated repeated visits from the same individuals. Nilgai cows occasionally used latrines; their use was sometimes followed by bulls showing flehmen responses after a female defecated or urinated on the latrine. We propose that dominant bulls use latrines for territory demarcation to display social dominance to both cows in estrus and subordinate bulls. Cows likely use latrines to communicate reproductive status. This study is the first intensive assessment focused on latrine ecology in nilgai. Our results directly contradict anecdotal descriptions of latrine use and behavior in nilgai but are consistent with predictions of antelope social systems based on body size, feeding type, and group dynamics.

Climate change in the Arctic has widespread and complex effects on the health of animals and their populations. We used radioimmunoassay to measure blubber cortisol in ringed seals (Pusa hispida) sampled in Ulukhaktok, Inuvialuit Settlement Region, Northwest Territories, Canada (spring, 2002, 2004–2005, 2007–2012) and Arviat, Nunavut, Canada (autumn, 2003–2012) to examine chronic stress relative to biology (age, sex, length), body condition (blubber depth), and diet (δ¹³C, δ¹⁵N, and isotopic niche size). Ulukhaktok ringed seals had higher cortisol concentrations overall (0.46 ± 0.04 ng/g) than Arviat ringed seals (0.36 ± 0.03 ng/g), and these higher concentrations were associated with higher muscle δ¹⁵N and lower blubber thickness. In contrast, blubber cortisol concentrations for Arviat ringed seals decreased with blubber depth and increased with age, though testing of age effects individually suggests that age-related patterns are weak. Annual mean cortisol concentration increased from 2003 to 2012 in Arviat ringed seals, but low sample sizes precluded analysis of annual patterns for Ulukhaktok ringed seals. The trend of increased cortisol over time in Arviat ringed seals suggests that they might be experiencing greater chronic stress over time, which could have implications for numerous population health metrics including reproduction and pup recruitment.

The woodrats or packrats of the genus Neotoma have been the subject of a wide array of research including paleoecology, physiology, morphological evolution, systematics, speciation, and hybridization. In recent years, much work has been done to elucidate evolutionary relationships within and between closely related species of the genus; in particular the addition of newly collected specimens from critical geographic regions has provided new opportunities for taxonomic assessment. Given these new data and their potential, parsimony (PARS), maximum likelihood (ML), and Bayesian inference (BI) analyses were conducted on DNA sequences obtained from nine individual genes (four mitochondrial loci: 12S, 16S, CoII, and Cytb; five nuclear loci: AdhI2, BfibI7, En2, Mlr, and Myh6) to estimate the phylogenetic relationships among 23 species of Neotoma. Results of these analyses depicted a wide array of phylogenetic relationships among taxa; with substantial nodal support recovered in both the ML and PARS analyses at some mid-level and terminal positions. Several individual genes, particularly 12S, AdhI2, BfibI7, CoII, and Cytb, provided support at several basal positions; however, phylogenetic resolution was limited in the other genes. A final BI analysis where the nine genes were concatenated into a single data set produced several supported clades that corresponded to previously recognized species groups (floridana, micropus, mexicana, and lepida) and the subgenus Homodontomys. Levels of genetic divergence for within-species comparisons (estimated from the Cytb data set) ranged from 0.88% (N. magister) to 6.82% (N. fuscipes); for between sister species comparisons ranged from 4.68% (N. devia and N. lepida) to 12.70% (N. angustapalata and N. nelsoni); and for members within closely related clades ranged from 8.70% (N. bryanti and N. lepida) to 12.57% (N. goldmani and N. magister). Evaluations of generic, subgeneric, and species group boundaries were explored using phylogenetic principles on the DNA sequence data presented herein, as well as morphological findings from previous studies. Results obtained suggest that the most conservative taxonomic interpretation involves the abandonment of subgeneric delineations and relies on the recognition of eight species groups (cinerea, floridana, fuscipes, lepida, mexicana, micropus, phenax, and stephensi) as the backbone of the woodrat classification.

Las ratas cambalacheras del género Neotoma han sido estudiadas en varios tipos de investigaciones incluyendo paleoecología, fisiología, evolución morfológica, sistemática, especiación e hibridación. Recientemente, se han realizado numerosos estudios para elucidar las relaciones evolutivas dentro del género y entre especies cercanamente relacionadas al mismo; en particular la inclusión de nuevos especímenes provenientes de regiones geográficas críticas han brindado nuevas oportunidades para evaluaciones taxonómicas. A partir de estos nuevos datos se realizaron análisis de parsimonia (PARS), Máxima Verosimilitud (MV), e Inferencia Bayesiana (IB) en secuencias de ADN provenientes de nueve genes individuales (cuatro loci mitocondriales: 12S, 16S, CoII, y Cytb; cinco loci nucleares: Adh-I2, Bfib-I7, En2, Mlr, and Myh6) para determinar la relación filogenética de 23 especies de Neotoma. Los resultados de estos análisis presentan una amplia gama de relaciones filogenéticas entre taxa con un soporte nodal importante en los análisis de MV y PARS en algunas posiciones terminales de nivel medio. Varios genes individuales, en particular 12S, Adh-I2, Bfib-I7, CoII, and Cytb, ofrecieron soporte en varias posiciones basales; sin embargo, la resolución filogenética fue reducida en los demás genes. El último análisis de IB, en donde nueve genes se concatenaron en un solo conjunto de datos, produjo soporte en varios clados que correspondieron a especies de grupos previamente reconocidos (floridana, micropus, mexicana, y lepida) y el sub-género Homodontomys. Los niveles de divergencia genética para comparaciones intraespecíficas fluctuaron entre 0.88% (N. magister) y 6.82% (N. fuscipes); para especies hermanas (4.68%—N. devia y N. lepida hasta 12.70%—N. angustapalata y N. nelsoni); y para los miembros de clados cercanos (8.70%—N. bryanti y N. lepida hasta 12.57%—N. goldmani y N. magister). Las evaluaciones de los limites genéricos, subgenéricos y de grupos de especies fueron explorados usando principios filogenéticos en las secuencias de ADN de este trabajo, y también se basaron en las conclusiones morfológicas de estudios previos. Los resultados obtenidos sugieren que la interpretación taxonómica más conservadora incluye el abandono de las delineaciones subgenéricas y se depende en el reconocimiento de ocho grupos de especies (cinerea, floridana, fuscipes, lepida, mexicana, micropus, phenax, y stephensi) como el pilar central de la clasificación de las ratas cambalacheras.

The Nelson's small-eared shrew (Cryptotis nelsoni) is a mammal at high risk of extinction and endemic to the cloud forest in the mountains of Los Tuxtlas, an isolated volcanic field in eastern México. It is a little-known species that remained unrecorded for over a century. However, recent works have increased the number of museum specimens and tissue samples of C. nelsoni, which we studied here to improve our knowledge of their taxonomy and conservation status. We compared the morphology and DNA barcode sequences of C. nelsoni against its three most closely related species. We also evaluated the possible effect of anthropogenic climate change on this mountain species according to three general circulation models and two scenarios proposed for the year 2050. The results showed that the skull and postcranial variables could easily discriminate C. nelsoni from the other species in terms of body size, to which some distinctive qualitative characteristics related to the width of the snout and the curvature of the humerus also contribute. DNA barcoding also helped identify the shrew species accurately, with a genetic distance of more than 6% from its closest species. The morphological and genetic characteristics highlight the evolutionary distinctiveness of C. nelsoni. Unfortunately, warmer extremes and higher rainfall than today could pose a severe threat to the survival of this shrew for decades to come, even in the most optimistic scenarios.

La musaraña de orejas pequeñas de Nelson (Cryptotis nelsoni) es un mamífero en alto riesgo de extinción y endémico del bosque de niebla en las montañas de Los Tuxtlas, un campo volcánico aislado en el este de México. Es una especie poco conocida que permaneció sin ser registrada durante más de un siglo. Sin embargo, trabajos recientes han aumentado el número de ejemplares de museo y muestras de tejido de C. nelsoni, los cuales estudiamos aquí para mejorar nuestro conocimiento de su taxonomía y estado de conservación. Comparamos la morfología y secuencias de códigos de barras de ADN de C. nelsoni con sus tres especies más estrechamente relacionadas. También evaluamos el posible efecto del cambio climático antropogénico sobre esta especie de montaña, de acuerdo con tres modelos de circulación general y dos escenarios propuestos para el año 2050. Los resultados mostraron que el cráneo y las variables postcraneales pueden discriminar fácilmente C. nelsoni de las otras especies en términos del tamaño corporal, a lo que también contribuyen algunas características cualitativas distintivas relacionadas con el ancho del hocico y la curvatura del húmero. Los códigos de barras de ADN también ayudaron a identificar con precisión a C. nelsoni, con una distancia genética de más del 6% respecto a la especie más cercana. Las características morfológicas y genéticas resaltan el carácter evolutivo distintivo de C. nelsoni. Desafortunadamente, extremos más cálidos y precipitaciones más altas que en la actualidad podrían representar una grave amenaza para la supervivencia de esta musaraña en las próximas décadas, incluso en los escenarios más optimistas.