Following dispersal from 1 group, individuals may join other established social groups. Such intergroup transfer may increase access to potential mates and decrease mate competition. We used data from 402 individuals to examine patterns of intergroup transfer in prairie voles (Microtus ochrogaster). Nearly 32% of established social groups (single female units, male–female pairs, or communal groups of at least 2 adults of the same sex) were joined by 1 or more individuals. Most individuals (76%) that joined social groups were wanderers that were either unmarked, recently marked during grid trapping, or marked transients; 70% were males. Joining a group was not contingent upon recent disappearance of residents. Total number of residents positively affected the probability of a female joining a social group, whereas number of adult female residents and population density negatively affected it. Some individuals (24%) moved directly from one group to another without an intervening wandering stage; we refer to these instances of intergroup transfer as direct transfers. Most direct transferers moved into nearby groups, but not the closest group. Males were more likely than females to directly transfer into groups with potential mates and without potential competitors. Thus, males directly transferred in a manner consistent with maximizing reproductive opportunities. In contrast, 25% of females directly transferred into groups without potential mates and 96% into groups with at least 1 adult female. Females may be less constrained by group composition with respect to potential mates because wandering males, with which females can mate, are prevalent. All-male groups almost never occur in our population, so females probably cannot avoid joining groups with competitors.

Many animals depend on nests for their survival and reproduction, with some species considered obligate tree cavity-nesters. Mearns's squirrel (Tamiasciurus mearnsi) is a species endemic to the Sierra de San Pedro Mártir, Baja California, Mexico, that relies on tree cavities for nesting. Federally listed as threatened in Mexico, and as endangered by the International Union for Conservation of Nature, the ecology of this southernmost Tamiasciurus is poorly known. The aim of this study was to examine the nesting requirements of Mearns's squirrels. We used telemetry to locate the nests and 10-m-radius circular plots to compare habitat characteristics between nest sites and random sites, nest sites of males and females, and nest sites of breeding and nonbreeding females. Nest tree species, nest tree condition, nest tree size (diameter at breast height), canopy cover, and occurrence of white firs (Abies concolor) are important characteristics for nesting. Nest sites of males did not differ from those of females except for nest tree condition. Females apparently do not have specific nesting requirements for rearing young. Unlike other congeners that also build leaf nests and underground burrows for nesting, large trees and snags that facilitate cavity formation are critical for the conservation of this species.

Muchos animales dependen de nidos para su sobrevivencia y reproducción con algunas especies consideradas anidadoras de cavidad obligadas. La ardilla de Mearns (Tamiasciurus mearnsi) es una especie endémica de la Sierra de San Pedro Mártir, Baja California, México, la cual depende de cavidades de árboles para anidar. Listada federalmente como amenazada en México, y como en peligro por la Unión Internacional para la Conservación de la Naturaleza, la ecología de esta Tamiasciurus sureña es pobremente conocida. El objetivo de este estudio fue examinar los requerimientos de anidación de las ardillas de Mearns. Utilizamos telemetría para localizar los nidos y cuadrantes circulares de 10 m de radio para comparar características del hábitat entre los sitios de anidación y sitios al azar, sitios de anidación de machos y hembras, y sitios de anidación de hembras reproductivas y no reproductivas. La especie del árbol de anidación, la condición del árbol de anidación, el tamaño (diámetro a la altura del pecho) del árbol de anidación, la cobertura del dosel y la abundancia de abetos blancos (Abies concolor) son características importantes para anidar. Los sitios de anidación de los machos no difirieron de las hembras excepto por la condición del árbol de anidación. Las hembras aparentemente no tienen requerimientos específicos de anidación al tener crías. A diferencia de otros congéneres que también construyen nidos de hoja y madrigueras subterráneas para anidar, los árboles grandes y tocones que facilitan la formación de cavidades son críticos para la conservación de esta especie.

Rodents make foraging decisions by balancing demands to acquire energy and mates with the need to avoid predators. To identify variations in the risk of predation, nocturnal rodents may use moonlight as a cue of risk. Moonlight avoidance behaviors have been observed in many nocturnal rodent species and are widely generalized to small mammals. However, most prior studies have been limited to 1 species or 1 study site, or occurred in modified habitats. We evaluated desert rodent activity patterns in natural habitats from 1999 to 2006 at 62 study sites across the Great Basin Desert of western North America. Rodent activity was examined by livetrapping in open habitats, using the presence of the sand-obligate kangaroo mouse (Microdipodops) as a habitat indicator. Activity patterns were assessed on 69 nights with clear skies and compared to corresponding moonlight values (moon phase and brightness) to evaluate the frequency of moonlight avoidance. Analyses of total activity of all species in the rodent assemblage relative to moonlight showed a distinct nonrandom (triangular-shaped) pattern but no significant correlations. However, individual genera of desert rodents responded differently to moonlight. Only kangaroo rats (Dipodomys) displayed significant moonlight avoidance patterns; they were maximally active at significantly different moonlight levels and avoided bright moonlight to a greater extent than co-occurring rodents. Moonlight seemed to limit the activity of kangaroo rats most strongly on bright nights during waxing moon phases and summer seasons, but not significantly during the spring or fall seasons, or during waning moons. Rather than avoiding moonlight, the activity of deer mice (Peromyscus), pocket mice (Perognathus), and kangaroo mice may be governed by changes in competition with kangaroo rats. Differences in the body size, locomotion, and space use of kangaroo rats relative to other rodents may explain why different moonlight responses were detected, especially if these traits alter how rodents perceive risk from bright moonlight. These findings indicate that moonlight avoidance may be a specialized trait of kangaroo rats rather than a general behavior of nocturnal desert rodents in the Great Basin.

Use of photographic capture–recapture analyses to estimate abundance of species with distinctive natural marks has become an important tool for monitoring rare or cryptic species, or both. Two different methods are available to estimate density: nonspatial capture–recapture models where the trap polygon is buffered with the half or full mean maximum distance moved by animals captured at more than 1 trap (1/2 MMDM or MMDM, respectively); or spatial capture–recapture (SCR) models that explicitly incorporate movement into the model. We used data from radiotracked Eurasian lynx (Lynx lynx) in the northwestern Swiss Alps (NWSA) during a low (1.0 lynx/100 km²) and a high (1.9–2.1 lynx/100 km²) lynx population density to test if lynx space use was density dependent. Second, we compared lynx density estimates resulting from these 2 different methods using camera-trapping data collected during winters 2007–2008 and 2009–2010 in the NWSA. Our results indicated lynx space use was negatively correlated with density. Lynx density estimates in all habitats using MMDM (0.86 and 0.97 lynx/100 km² in winters 2007–2008 and 2009–2010, respectively) were significantly lower than SCR model estimates, whereas there was no significant difference between SCR model (1.47 and 1.38) and 1/2 MMDM (1.37 and 1.51) density estimates. In the NWSA, which currently harbors the most abundant lynx population in Switzerland, 1/2 MMDM and SCR models provided more realistic lynx density estimates compared to the MMDM, which lies in the lower range of densities. Overall, the SCR model is preferable because it considers animal movements explicitly and is not biased by an informal estimation of the effective sampling area.

The small (2- to 7-kg) leopard cat (Prionailurus bengalensis) is the most common cat species in Asia. Although it occurs in a wide range of habitats and seems to adapt well to anthropogenic habitat changes, surprisingly little is known about this species in the wild. All studies have focused on protected areas, although a large proportion of Southeast Asian forests are timber concessions. During this study, we used large camera-trapping data sets (783 records of 124 individuals) from 3 commercially used forests to investigate consequences of different logging regimes on density and habitat associations of the leopard cat. We applied spatial capture–recapture models accounting for the location of camera-traps (on or off road) to obtain estimates of leopard cat density. Density was higher in the 2 more disturbed forest reserves (X̄ = 12.4 individuals/100 km² ± 1.6 SE and 16.5 ± 2 individuals/100 km²) than in the sustainably managed forest (9.6 ± 1.7 individuals/100 km²). Encounter rates with off-road traps were only 3.6–9.1% of those for on-road traps. Occupancy models, which accounted for spatial autocorrelation between sampling sites by using a conditional autoregressive model, revealed that canopy closure and ratio of climax to pioneer trees had a significantly negative impact on leopard cat occurrence. Our results confirm that the leopard cat is doing well in modified landscapes and even seems to benefit from the opening of forests. With such flexibility the leopard cat is an exception among tropical rain-forest carnivores.

Sperm competition has received much attention in recent years as a primary form of intrasexual competition among males, but little is known about variation in ejaculate quality in natural mammal populations, particularly among carnivores. Here, we documented variation in semen characteristics among wild male spotted hyenas (Crocuta crocuta). We then tested hypotheses suggesting that reproductive senescence among aging male hyenas is reflected in declining ejaculate quality, and that dispersal status affects ejaculate quality. To address these questions, we electroejaculated 20 wild males, including both immigrants and adult natal males. We found no support for the hypothesis that male spotted hyenas experience reproductive senescence with respect to their ejaculate quality, but we did find that immigrant males had significantly higher ejaculate quality than adult natal males, suggesting that adult natal males may experience reproductive suppression before dispersing. Finally, to test the assumption that an individual's ejaculate quality is consistent over time, we obtained repeated samples from 6 captive male hyenas. This captive work demonstrated significant individual repeatability in ejaculate quality and illustrated the utility of complementing field research with laboratory study. By exploring variation in ejaculate quality and its relationship with life-history traits in this unique species, we have highlighted new avenues for potential research regarding how sexual selection manifests in sex role–reversed species.

Many demographic parameters of imperiled fishers (Martes pennanti) in the Pacific Northwest remain poorly understood but are necessary to develop conservation strategies; herein we report on fisher reproduction, recruitment, and dispersal on the Hoopa Valley Indian Reservation, California, to help fill key knowledge gaps. Forty radiocollared, breeding-age females exhibited denning behavior on 80 (87%) of 92 opportunities between 2005 and 2011. Twenty-eight female fishers weaned offspring in 55 (65%) of 85 adequately monitored denning opportunities. Two-year-old female fishers were less likely than older females to den and wean kits. We counted 52, and extracted and marked 51, kits comprising 28 litters of 19 females between 2005 and 2008. Average litter size was 1.9 kits (27 females, 24 males, and 1 unknown) 4–12 weeks postbirth. Mean distances between natal dens and centroids of newly established ranges for 7 juvenile females was 4.0 km (range = 0.8–18.0 km); this distance for 1 male was 1.3 km. The recruitment rate of juveniles that successfully established a home range per adult female was 0.19 (0.16 for females and 0.02 for males). Our results suggest that managers should work toward increasing female survival rates and consider translocations to increase and expand existing fisher populations.

The aim of this study was to examine the effects of sex and age of individuals, season, and human pressure (both human presence and habitat structure) on spatiotemporal behavior of wild boar (Sus scrofa). Specifically, we compared wild boar behavior under contrasting conditions of human pressure, within the primeval temperate forest of Białowieża (eastern Poland) and the metropolitan area of Cracow (Poland). It was predicted that, compared with the forest, wild boar within the urban area will have smaller home ranges due to restricted space, will show longer daily movements due to patchy resources, and will exhibit increased nocturnal activity and ranging behavior in an attempt to avoid human interference. We used radiotracking data from 35 wild boar. Animals inhabiting the urban area had smaller home ranges, yet covered almost twice as much distance on a daily basis than individuals inhabiting primeval forest. Daily duration of activity was similar in the 2 study areas. However, distribution of activity throughout the day differed considerably. In the urban area wild boar were almost exclusively nocturnal, whereas in the primeval forest wild boar activity was evenly distributed throughout the day. Additionally, in the urban area, activity was strongly associated with traveling speed, whereas in the primeval forest active wild boar moved about to little extent. Seasonal effects were stronger in the primeval forest and affected daily distance traveled, duration of activity, and level of diurnality. This study showed that wild boar can adjust their spatiotemporal behavior to local conditions and this may be one factor explaining recent rapid demographic expansion in Europe.

Much research has been directed at the chemical characteristics of plants that influence forage digestibility but there is less investigation into relationships between chewing and foraging in herbivores. The role of body size on forage processing, via chewing, and ingestive behavior is poorly understood in spite of associations between conspecific body size of ruminants and botanical and nutritional composition of their diets. I examined the implications from a relationship between body weight and absolute forage intake (kg/day) and no relationship between body weight and rumination time (h/day) on chewing behavior and feeding time (h/day). Cattle were selected as the model species because the diets presented offered benefits to digestion from increased chewing and because of the number of studies that measured body weight, daily food intake, dietary nutritional characteristics, feeding time, and rumination characteristics on the same individuals. Data were extracted from 24 studies of cattle (n ≤ 74). Absolute food intake scaled allometrically (0.75) with body weight but rumination time was unrelated to body weight, meaning smaller animals had more rumination time for a unit weight of ingesta. Correspondingly, small cattle chewed the weight-specific ingesta more and fed longer than large animals, probably because of a reduction in time of rumen turnover. These findings might be revealing as to how differences in digestion and foraging are associated with body size among conspecific animals of wild ruminant species.

Factors affecting juvenile survival are poorly known in the world's most northern antelope, the endangered saiga (Saiga tatarica), yet these factors are fundamental for understanding what drives population change. We monitored Mongolia saiga (S. tatarica mongolica) calves in Sharga Nature Reserve, western Mongolia, during 2008–2010. Our results showed that male and single calves were heavier than females and twins, respectively. However, we identified no significant differences in seasonal or annual survival rates between sexes or between singletons and twins. Litter size and birth mass varied among years, and there was a negative relationship between these variables. Survival of calves during the 1st year was best explained by the covariates of year and litter size (confounded with body mass), suggesting that interannual variation in environmental conditions influenced twinning rates and body mass, and might play a key role in 1st-year survival. We identified 3 sources of mortality—predation by raptors, foxes (red fox [Vulpes vulpes] and corsac fox [V. corsac]), and lynx (Lynx lynx). Most predation was attributed to raptors, such as golden eagles (Aquila chrysaetos) and cinereous vultures (Aegypius monachus). Our results point to both environmental and biotic factors affecting survival of juvenile saiga.

White-lipped peccaries (Tayassu pecari) are important seed predators and dispersers throughout the Neotropics. Because they occur in groups as large as 300 individuals, they need large areas to persist. We investigated home-range size and overlap of 13 groups using radiotelemetry data from 3 years of monitoring in the Emas National Park and surrounding farmland in central Brazil. Average home-range sizes were 1,710.64 ha for 50% of the locations and 8,659.99 ha for 95% based on minimum convex polygons and 790.38 ha for 50% of the locations and 7,986.92 ha for 95% based on the fixed kernel estimator. Home-range size did not correlate with group size, the monitoring period, or the number of locations obtained. Home ranges were larger during the wet season than the dry season. Average home-range overlap among groups was 31%; there were no significant differences in overlap between seasons. Home ranges varied seasonally, most likely in response to the dynamic landscape of crop plantations surrounding the park. Although the peccaries fared well in the heterogeneous agricultural landscape surrounding the park, conflict with farmers due to crop damage and landscape changes due to expansion of sugarcane plantations need to be addressed by conservation strategies.

Queixadas (Tayassu pecari) são importantes predadores e dispersores de sementes ao longo da região Neotropical. Como ocorrem em grandes grupos chegando a 300 indivíduos, necessitam de grandes áreas para sobreviver. Nós investigamos o tamanho e a sobreposição da área de vida de 13 grupos usando dados de radio-telemetria de três anos de monitoramento no Parque Nacional das Emas e nas propriedades rurais de seu entorno, no Brasil central. Os tamanhos médios das áreas de vida foram 1,710.64 ha para 50% das localizações e 8,659.99 ha para 95%, utilizando o método do Polígono Mínimo Convexo, e 790.38 ha para 50% das localizações e 7,986.92 ha para 95%, utilizando o método kernel. Não houve correlação entre os tamanhos das áreas de vida, tamanhos dos grupos, período de monitoramento ou número de localizações obtidas. As áreas de vida na estação chuvosa foram significantemente maiores do que as áreas de vida na estação seca. A média de sobreposição das áreas de vida entre os grupos foi de 31%; não ocorreu diferença significativa nas sobreposições de áreas de vida entre estações. As áreas de vida mostraram variação sazonal, provavelmente como uma resposta à dinâmica da paisagem de lavouras no entorno do Parque. Embora a espécie esteja adaptada a esta paisagem antropizada, os problemas relacionados ao conflito com agricultores em decorrência dos prejuízos causados nas lavouras, bem como a substituição de lavouras tradicionais pela de cana-de-açúcar, precisam ser considerados em futuras estratégias de conservação.

Milk is essential to a mammalian mother's reproductive strategy and is necessary for offspring growth and development. In hibernators with a short duration between weaning and winter immergence, milk synthesis is likely constrained by time and trade-offs between maternal and offspring condition, thus influencing milk composition. We characterized the proximate and mineral composition of milk produced by a hibernating rodent, the Columbian ground squirrel (Urocitellus columbianus). The concentration of all milk components varied across lactation; the concentration of most constituents peaked between days 14 and 19 postpartum. Columbian ground squirrel milk was relatively low in lipids but high in protein and calcium. At peak lactation, milk was composed of 10.71% ± 0.46% SE protein, 9.15% ± 0.47% lipids, 3.39% ± 0.13% sugar, and 0.47% ± 0.02% calcium (wet mass basis). High protein, energy from protein, and calcium in milk corroborate earlier reports of the importance of fast growth rates of juveniles to overwinter survival, whereas the low lipid content of milk may reflect fat conservation for adults. Production of high-calcium milk also may be a preventive mechanism enabling offspring to cope with bone mineral loss during hibernation.

Differential investment in offspring has been reported for many mammals, often in the context of the Trivers–Willard model of male-biased investment, but evidence of differential investment in pronghorns (Antilocapra americana) is largely lacking. We assessed the causes and consequences of different birth masses of littermate fawns in a pronghorn population in Oregon. The mass differential for co-twins ranged from 0% to 89% (median = 8.35%). Male-biased investment explained the mass differential in opposite-sex litters but not same-sex litters. The mass differential did not result from mothers producing 1 normal-size fawn and 1 runt fawn, and the smaller fawn was not deficient in physiological condition. Only 29% of fawns survived to 8 weeks and both fawns died in 56% of litters, but co-twin mortalities were largely separate events. Mass did not confer a survival advantage when considering all fawns through age 8 weeks, but there was evidence of such an advantage when comparing fawns within litters before age 18 days. Differential investment in fawns might be a bet-hedging strategy in which the mother accepts a lower expected reproductive success in exchange for a lower variance, but neither the mean nor the variance differed between mothers of different-size (>8.35% mass differential) and similar-size (<8.35%) litters. In fact, there was evidence of increased reproductive success for mothers of different-size litters, much of which stemmed from higher survival 4–6 days after birth. Having different-size fawns reduced the chances of sequential mortality, in which a predator killed one fawn then returned to kill the other.

The principle of energy allocation states that individuals should attempt to maximize fitness by allocating resources optimally among growth, maintenance, and reproduction. Such allocation may result in trade-offs between survival and reproduction, or between current and future reproduction. We used a marked population of North American elk (Cervus elaphus) to determine how energetic costs of reproduction in the current year affect survival and reproduction in the subsequent year. Using a multistate mark–recapture model we examined the influence of individual and environmental variation on trade-offs between these 2 life-history traits. We observed no difference in survival probabilities between pregnant and nonpregnant individuals or as a function of recruiting an offspring. Nonetheless, there was a negative effect of recruiting an offspring in the current year on becoming pregnant the following year. Increased body condition, and higher precipitation, contributed to greater probabilities of becoming pregnant in a particular year regardless of reproductive state and previous recruitment. Costs associated with reproduction led to a reduced probability of future reproduction rather than a reduction in survival. These findings are consistent with risk-sensitive reproductive allocation, where adult survival is maintained through variation in reproductive effort resulting in high and stable adult survival and more-variable reproduction.

Because of a rapidly changing climate, the need to understand how populations respond to varying climatic conditions has become increasingly important. Using long-term data from an unhunted population of Alpine chamois (Rupicapra rupicapra) and autoregressive time series models we investigated the extent to which the population demography was affected by local climate. Because density and weather are likely to operate differently on various sex–age categories, anticipated effects were assumed to vary among categories. Generally, elevated densities in 1 year negatively influenced the subsequent change in population size. Severe snow conditions during late winter negatively affected total population growth, and growth of the male, yearling, and juvenile segments of the population. A lagged effect of early winter snow on the change in animal numbers was demonstrated for females. Winter temperatures positively affected the growth rate of juveniles, whereas they appeared to have negative consequences for male and yearling growth rates. The juvenile–female ratio was negatively affected by the current female density, but did not respond to the various climate variables. Winter survival of juveniles was negatively influenced by the juvenile number during the preceding summer and harsh snow conditions during early winter. Our results indicate that winter climate shapes the demography of Alpine chamois. Particularly, winters with a lot of snow might have long-lasting consequences for the population. Considering the juveniles, lagged effects apparently operate through the body condition of their mothers. The conflicting effects of temperature on the different sex–age categories make the direction of expected population response to global warming difficult to predict.

Treeshrews (order Scandentia) comprise 2 families of squirrel-sized terrestrial, arboreal, and scansorial mammals distributed throughout much of tropical South and Southeast Asia. The last comprehensive taxonomic revision of treeshrews was published in 1913, and a well-supported phylogeny clarifying relationships among all currently recognized extant species within the order has only recently been published. Within the family Tupaiidae, 2 widely distributed species, the northern treeshrew, Tupaia belangeri (Wagner, 1841), and the common treeshrew, T. glis (Diard, 1820), represent a particularly vexing taxonomic complex. These 2 species are currently distinguished primarily based on their respective distributions north and south of the Isthmus of Kra on the Malay Peninsula and on their different mammae counts. This problematic species complex includes 54 published synonyms, many of which represent putative island endemics. The widespread T. glis and T. belangeri collectively comprise a monophyletic assemblage representing the sister lineage to a clade composed of the golden-bellied treeshrew, T. chrysogaster Miller, 1903 (Mentawai Islands), and the long-footed treeshrew, T. longipes (Thomas, 1893) (Borneo). As part of a morphological investigation of the T. glis–T. belangeri complex, we studied the proportions of hand bones, which have previously been shown to be useful in discriminating species of soricids (true shrews). We measured 38 variables from digital X-ray images of 148 museum study skins representing several subspecies of T. glis, T. belangeri, T. chrysogaster, and T. longipes and analyzed these data using principal components and cluster analyses. Manus proportions among these 4 species readily distinguish them, particularly in the cases of T. chrysogaster and T. longipes. We then tested the distinctiveness of several of the populations comprising T. glis and T. longipes. T. longipes longipes and T. l. salatana Lyon, 1913, are distinguishable from each other, and populations of T. “glis” from Bangka Island and Sumatra are distinct from those on the Malay Peninsula, supporting the recognition of T. salatana, T. discolor Lyon, 1906, and T. ferruginea Raffles, 1821 as distinct species in Indonesia. These relatively small, potentially vulnerable treeshrew populations occur in the Sundaland biodiversity hotspot and will require additional study to determine their appropriate conservation status.

The garden dormouse, Eliomys quercinus (Rodentia, Gliridae), displays a surprisingly high karyotypic diversity, with the number of chromosomes varying between 2N = 48 and 2N = 54. We aimed to assess whether the karyotypic diversity is congruent with the mitochondrial differentiation of the populations; improve our understanding of the taxonomic relationships between garden dormouse populations based on both chromosomal and mitochondrial information; and establish the phylogeographic history of the species and the time of differentiation of mitochondrial lineages of E. quercinus and E. melanurus. For this purpose we sequenced the mitochondrial cytochrome-b (Cytb) gene for 62 E. quercinus and 4 E. melanurus from 27 localities representing all the known chromosomal races of the genus Eliomys in the western Palearctic region. Our results 1st showed that populations of E. quercinus are separated into 4 evolutionarily significant units partially congruent with the chromosomal races and corresponding to Iberian (2N = 48), Italian (2N = 48 or 50), western European (2N = 48, 49, or 50), and Alpine (2N = 52 or 54) mitochondrial lineages or clades. The existence of hybrid individuals between chromosomal races and the presence of several chromosomal races within each mitochondrial lineage both indicate that gene flow persists between chromosomal races. Second, we estimated that the major mitochondrial lineages differentiated from each other around 4.2 ± SD 1 million years ago, thus predating the Quaternary glaciations. Third, E. quercinus displayed a higher haplotypic variability in the Mediterranean peninsula than in the northwestern European populations. However, E. quercinus did not show a pattern of postglacial recolonization of northwestern Europe from Iberian or Italian populations. Our results also suggest that additional, unexpected refuge regions around the Alps exist for the species. Such information will be useful for deciphering the priorities for the protection of E. quercinus, which is listed as “Near Threatened” on the International Union for the Conservation of Nature Red List of Threatened Species and is protected by Appendix III of the Bern Convention.

Past climatic fluctuations have had a significant impact on the patterns of genetic variation within taxa restricted to montane regions and forested biomes; however, little is known about whether equivalent processes have occurred in arid biomes. Northwestern Namibia's inselbergs provide a unique ecosystem in which to study the effects of major climatic events and geographical isolation on the genetic structuring of taxa in a subtropical arid biome. We investigated the phylogeographic structure of the black mongoose (Galerella nigrata), an inselberg habitat specialist endemic to this region, using mitochondrial DNA (mtDNA) haplotypes (cytochrome b, 1,089 base pairs) and nuclear microsatellite genotypes (15 loci) from 6 inselberg populations. Analyses of molecular variance and spatial analyses of molecular variance of the 14 mtDNA haplotypes identified 2 significant geographic barriers to the dispersal of black mongooses; these barriers occurred across the vast arid plains between Ruacana and Hobatere, and between Ohorongo and inselbergs to the south. The occurrence of mtDNA haplotypes that were restricted to specific populations also indicated some degree of isolation, likely resulting from limited gene flow and drift induced by the desertification of the landscape between inselbergs during the lead-up to the most recent glacial maxima. Despite this pattern of isolation, the widespread distribution of 1 mtDNA haplotype suggested that populations of black mongoose have, in general, been well connected in the past. Ongoing gene flow was further supported by Bayesian clustering of microsatellite genotypes, which showed 2 clusters, each spread across the mongoose's distribution, and a lack of significant differentiation between populations. In addition, a constant population size was indicated by a Bayesian skyline plot. These analyses suggested that inselbergs across the entire study area might have supported black mongoose populations during some or all of the most recent major climatic fluctuations, with periods of isolation during glacial maxima and reestablished connectivity during interglacial periods.

On the basis of an adult individual collected in 1955 plus 3 mandibles of latest Holocene age, we describe a new living species of the amphibious rat Holochilus (Sigmodontinae, Oryzomyini) from west-central Mendoza Province, Argentina. The new species is characterized by its short tail, broad zygomatic plate with rounded anterior–superior corner, bony palate without excrescences, large mesolophostyle in the upper first molars and complex upper third molar shorter than the second, and lacking the hypoflexus. The morphological traits displayed by this new Holochilus combine features observed in both the H. brasiliensis and H. sciureus groups with others unique among the genus (e.g., absence of hypoflexus). This new species is the southernmost expression of the genus along the western side of its current range, where it appears isolated in the middle part of the Río Atuel. The finding reported here uncovers and highlights unexpected diversity in southern South American arid lands.

En base a un individuo adulto obtenido en 1955 y tres mandíbulas del Holoceno más tardúo se describe una nueva especie viviente de la rata anfibia Holochilus (Sigmodontinae, Oryzomyini) del centro-oeste de la provincia de Mendoza, Argentina. La nueva especie se caracteriza por su cola corta, placa zigomática ancha con el extremo anterodorsal redondeado, paladar óseo sin excrecencias, primeros molares superiores con mesolofostilos bien desarrollados y tercer molar superior complejo sin hipoflexo y más corto que el segundo molar superior. Los rasgos morfológicos que muestra esta nueva especie de Holochilus combinan características observadas en los grupos de especies de H. brasiliensis y H. sciureus como así también otras únicas en el contexto del género (e.g., ausencia de hipoflexo). Esta nueva especie es la expresión más austral del género en la porción occidental de su rango de distribución y parece estar aislada en el cauce medio del río Atuel. El hallazgo reportado aquí destaca una diversidad insospechada en las tierras áridas del sur de América del Sur.