The availability of complete genome sequences and genetic linkage maps for a growing number of mammalian species is opening up exciting new opportunities for studies of evolutionary change in natural populations. For example, multilocus mapping approaches hold the promise of identifying the specific genetic changes that underlie ecological adaptation and reproductive isolation. The fact that many of the genomic resources that have been developed for Mus and Rattus are transferable to other muroid rodents means that roughly 25% of all mammalian species can now be considered “genome-enabled” study organisms to varying degrees. The transferability of genomic resources between model organisms and their more ecologically interesting kin should usher in a renaissance period of research on adaptation and speciation in mammals.

Many traits exhibit nonequivalent effects upon maternal versus paternal inheritance. Such “parent-of-origin” effects may be caused by several mechanisms including sex chromosomes and maternal inheritance of mitochondrial DNA. Recently, a class of mammalian autosomal genes has emerged that shows expression of only 1 parental allele. This phenomenon has been termed “genomic imprinting.” Genomic imprinting is an epigenetic effect resulting from chromosomal marks established during gametogenesis. Such imprinted genes result in non-Mendelian inheritance patterns despite being located on autosomes. The chorioallantoic placenta and brain are prominent places of imprinted gene expression. Correspondingly, most imprinted genes appear to be involved in growth or behavior. Interspecific variation in which genes display genomic imprinting suggests that the process is under selection. There is also evidence for intraspecific variation in degree of imprinting of certain genes. Here I briefly review the current understanding of imprinting mechanisms and arguments for selection. The leading argument for positive selection of genomic imprinting is an extension of the concept of kin selection. Although this hypothesis remains controversial, the involvement of imprinted genes in placentation suggests a role in reproductive isolation. Interspecific hybrids in the cricetid genus Peromyscus exhibit parent-of-origin effects involving placental and somatic growth dysplasias. Female P. maniculatus crossed with male P. polionotus produce neonates smaller than either parental strain, with placentas half the parental size. Female P. polionotus crossed with male P. maniculatus produce dysmorphic overgrown embryos whose placentas average >2.5 times the mass of the parental strains. Hybrid dysgenesis in Peromyscus is affected by both the imprinting process and interactions among imprinted genes. I hypothesize that imprinted genes underlie multiple cases of reproductive isolation in the P. maniculatus species complex. Further, I suggest that such interactions have played a significant role in generating mammalian diversity. Finally, I examine the role of the environment in regulating genomic imprinting and argue that studying natural populations in wild-type habitats will be critical to understanding this phenomenon.

Understanding the biochemical mechanisms that enable high-altitude animals to survive and function under conditions of hypoxic stress can provide important insights into the nature of physiological adaptation. Evidence from a number of high-altitude vertebrates indicates that modifications of hemoglobin function typically play a key role in mediating an adaptive response to chronic hypoxia. Because much is known about structure–function relationships of mammalian hemoglobins and their physiological role in oxygen transport, the study of hemoglobin variation in high-altitude mammals holds much promise for understanding the nature of adaptation to hypoxia from the level of blood biochemistry to the level of whole-organism physiology. In this review I 1st discuss basic biochemical principles of hemoglobin function and the nature of physiological adaptation to high-altitude hypoxia in mammals. I then discuss a case study involving a complex hemoglobin polymorphism in North American deer mice (Peromyscus maniculatus) that illustrates how integrative studies of protein function and fitness-related physiological performance can be used to obtain evolutionary insights into genetic mechanisms of adaptation.

Many genes involved in reproduction have evolved at a rapid rate in diverse taxonomic groups. We use new data for the mammalian reproductive gene that encodes acrosin to document patterns of adaptive evolution and rapid divergence. Likelihood scores for neutral and selection models indicate that molecular evolution of the Acr gene is driven by positive selection. Comparisons of Acr sequences to mitochondrial genes and a nuclear intron show that reproductive genes can be informative phylogenetic markers. In bovid artiodactyls (cattle, sheep, goats, and antelopes), exon 5 of Acr is highly variable, is characterized by a low level of homoplasy, and has a fairly even spread of substitutions across the 3 codon positions. Impressive congruence with independent DNA data sets suggests that Acr, and perhaps additional rapidly evolving reproductive molecules, show promise for resolving evolutionary radiations of mammals.

In the early 1980s, 2 groups of Soviet scientists independently described 1, possibly 2 new dwarf species of killer whales (Orcinus) from Antarctica. We used aerial photogrammetry to determine total length (TL) of 221 individual Type C killer whales—a fish-eating ecotype that inhabits dense pack ice—in the southern Ross Sea in January 2005. We confirmed it as one of the smallest killer whales known: TL of adult females (with calves) averaged 5.2 m ± 0.23 SD (n = 33); adult males averaged 5.6 ± 0.32 m (n = 65), with the largest measuring 6.1 m. Female Type A killer whales—offshore mammal-eaters—from Soviet whaling data in the Southern Ocean were approximately 1–2 m longer, and males were 2–3 m (up to 50%) longer (maximum length 9.2 m). Killer whale communities from the North Atlantic and in waters around Japan also appear to support both a smaller, inshore, fish-eating form and a larger, offshore, mammal-eating form. We suggest that, at least in Antarctica, this degree of size dimorphism could result in reproductive isolation between sympatric ecotypes, which is consistent with hypotheses of multiple species of killer whales in the Southern Ocean.

Eyes from 75 narwhals (Monodon monoceros) were collected in West Greenland in 1993 and 2004 for the purpose of age estimation. Age estimates were based on the racemization of l-aspartic acid to d-aspartic acid in the nucleus of the eye lens. The ratio of d- and l-enantiomers was measured using high-performance liquid chromatography. The aspartic acid racemization rate (k_Asp) was estimated to be 0.001045/year ± 0.000069 SE by regression of d/l ratios on age estimated by length from 15 young narwhals (≤298 cm) and by earplug laminations from 13 fin whales (Balaenoptera physalus). The d/l ratio at age 0 ((d/l)₀) was estimated to be 0.0288 by regression of d/l ratios against the estimated age of the 15 young narwhals. The intercept of the regression slope, providing twice the (d/l)₀ value, was 0.05759 ± 0.00147 SE. The maximum estimated age was a 115-year-old (±10 SE) female. Asymptotic body length was estimated to be 396 cm for females and 457 cm for males, and asymptotic body mass was estimated to be 904 kg for females and 1,645 kg for males. Using the von Bertalanffy growth model, age at sexual maturity was estimated to be 6–7 years for females and 9 years for males.

The behavior of offshore bottlenose dolphins (Tursiops truncatus) in deep water and near oceanic islands is not well known. Using satellite-linked, time–depth recorders, we investigated the movements and dive behavior of offshore bottlenose dolphins in the deep waters surrounding the Bermuda Pedestal. Three dolphins were tracked from 5 to 45 days and traveled a mean distance of 28.3 km/day where mean water depth was −1,402.0 m ± 1,120.7 SD. Regular dives during the night (2100–0259 h local time) to depths greater than 450 m (8.9% of total dives), 46.4% of night dives lasting longer than 5 min, and high hematocrit values reveal the deep-diving capabilities of offshore bottlenose dolphins. During the day (0900–1459 h local time), dives tended to be shallow, with 96% of dives within 50 m of the surface, and of short durations, with 52.7% lasting less than 1 min. At dusk (1500–2059 h local time), the number of dives increased (X̄ = 72.4 ± 19.6), indicating a diel dive cycle. The dive patterns of bottlenose dolphins in Bermuda waters correlate with the reported nightly vertical migrations of mesopelagic prey along the steep-sided Bermuda Pedestal.

The measurement of circulating reproductive hormone levels provides a relatively noninvasive method for assessing reproductive status. We assessed seasonal changes in concentrations of progesterone and total estrogens from serum samples collected from live stranded (n = 199) and captive (n = 5) California sea lions (Zalophus californianus). Progesterone concentrations increased in the fall (September–November) in both pregnant and nonpregnant animals, with no significant difference associated with pregnancy. Progesterone concentrations were greater in pregnant animals in the spring (February–April) than in nonpregnant animals. Circulating estrogen concentrations in captive, nonpregnant sea lions increased in July and November, correlating with periods of estrus and implantation. These data provide a baseline for studying reproduction in California sea lions.

A well-preserved ungual of a pes documents the presence of Jefferson's ground sloth (Megalonyx jeffersonii) at the end of the Wisconsinan in North Dakota. This is the 1st report of M. jeffersonii in North Dakota, and one of few records from the upper Great Plains. An accelerator mass spectrometer radiocarbon age of 11,915 ± 40 years ago was obtained from the specimen, suggesting that the sloth resided in North Dakota during the Rancholabrean Land Mammal Age, just before extinction of the species. Palynological records from sites near the sloth occurrence and of the same age indicate that it resided in a cool, moist, spruce-dominated forest habitat in a riparian setting along the Missouri River. Its presence in that setting corroborates the notion that Jefferson's ground sloth was a browsing inhabitant of gallery forests associated with rivers. It is likely that M. jeffersonii used river valleys, such as the Missouri River valley, as migration routes.

Bat diversity peaks in neotropical lowland forests, where 70–100 species may coexist in local assemblages. Understanding of factors that promote and maintain this diversity requires a thorough knowledge of the ecology and behavior of individual species. We studied the movement pattern, focusing on range size and foraging strategy, of the small frugivorous bat Rhinophylla pumilio (Phyllostomidae), with particular emphasis on constraints females have to deal with when rearing young. Because of the scattered distribution of its main food resource, infructescences of epiphytes, we hypothesized that R. pumilio should spend most of its flight time searching for food. Because its small body size incurs higher flight costs in comparison to larger fruit-eating bats, we further proposed that it should feed within small foraging areas that are close to each other and that commuting flights between foraging areas should be short and infrequent, resulting in small home ranges. Furthermore, we predicted that lactating females would change range size as well as activity budget by performing more search flights to increase food intake for milk production and more commuting flights to feed their young during nighttime. We radiotracked 9 females (4 nonreproductive, 4 lactating, and 1 subadult) and 2 males in the primary rain forest of Nouragues, French Guiana, for a total of 49 nights. Supporting our initial prediction, the foraging strategy of R. pumilio was mostly restricted to short (40- to 120-m) search flights in a single, rather small foraging area (3.5–14.1 ha). We observed a decrease in flight distances and size of foraging area, and an increase in total flight time throughout the night in lactating females that probably transported their young and nursed them in their foraging areas at night. Finally, we propose that the sensitivity of R. pumilio to forest fragmentation reported in previous studies may in part be caused by its foraging strategy because it consists mostly of short-distance search flights that make it difficult or impossible, particularly for lactating females, to regularly cross broad expanses of inhospitable matrix in fragmented forests. Fragmentation may therefore decrease breeding success and foster population decline in this species.

Most previous studies considering intraspecific differences in bat echolocation call frequency among geographic groups have related this to morphological features not directly involved in producing the characteristics of the emitted signal. We related a pattern of intraspecific call differences to the size of nasal chambers (estimated from radiographs of museum specimens), expecting chamber dimensions to be functionally coupled with the sound source. Such a relationship is potentially informative in the context of competing hypotheses that account for call frequency differences. Allopatry has been a precursor to differences in echolocation call frequency between isolated populations of the Australian endemic orange leaf-nosed bat (Rhinonicteris aurantia (Gray, 1845); Pilbara isolate: 120.99 ± 1.91 kHz; compared with Kimberley region: 114.65 ± 1.98 kHz and Northern Territory: 114.62 ± 2.10 kHz). Correlations with morphological features not directly involved in signal production or modification were either moderate (nose-leaf width) or absent (forearm length). Overall nasal volume was shown to be relatively smaller in the Pilbara population, which had higher average call frequency. This relationship was expected given the suggested function of nasal chambers in impedance matching. The finding is significant because nasal chamber size was the only character observed to vary in a species that was otherwise conserved morphologically, suggesting adaptation and not a simple scaling relationship with body size that might be more indicative of drift. We consider that the combination of patterns from echolocation call frequency and associated morphological features, as well as neutral DNA markers, provide adequate support for recognition of the separate populations of R. aurantia for conservation, according to more recent concepts that consider ecological as well as genetic characters when allocating groups to evolutionarily significant units.

Niche theory predicts that coexisting species should differ ecologically, morphologically, or behaviorally in ways that minimize competition. We used an ecomorphological approach to determine how coexisting species in the Old World fruit bat genus, Cynopterus, assort in morphological and ecological space. The study was conducted in peninsular Malaysia where 4 species of Cynopterus are broadly sympatric. Interspecific separation in resource use was estimated along 3 main axes: habitat, based on abundance across a habitat gradient at 2 sites; trophic niche, inferred from a suite of cranial and postcranial characters; and locomotory behavior and efficiency, inferred from wing morphology. Habitat associations, overall size, and the size and shape of the trophic apparatus were all important in separating 2 or more species, whereas interspecific differences in wing morphology were minor. In combination, the results of this study suggest that relatively minor separation among Cynopterus species pairs along single axes of resource use is sufficient to counteract overlap on other axes, and permit the coexistence of potential competitors.

The first-cohort advantage hypothesis (FCAH) was formulated to explain patterns of biased sex ratios in litters of Virginia opossums (Didelphis virginiana). Females of this species typically produce 2 litters each season, and litters born early in a season are male-biased and those born later in the season are female-biased. Males born earlier are older and heavier in the next breeding season and likely to secure more mates. The hypothesis predicts fitness benefits to mothers that have more males in their 1st litter (the 1st cohort) each season. The feathertail glider (Acrobates pygmaeus), in Victoria, Australia, is another species that produces 2 litters per year and not all males mature before the start of the breeding season after their birth. Hence, feathertail gliders also might be expected to show a pattern of sex bias in litters consistent with the FCAH. They do not. This paper uses data from 2 field studies of feathertail gliders in Victoria over the past 18 years. Sex ratios were recorded for 53 first- and 42 second-cohort litters. There was a trend toward male-biased litters in the 1st cohort, but also in the 2nd, and neither group differed significantly from a binomial distribution of sex ratios. This provides no support for the FCAH in this species. This may be due to the much less sharply defined breeding seasons in feathertail gliders compared to those of Virginia opossums, and to their greater longevity.

Polygynous ungulates are commonly used to test the Trivers–Willard hypothesis that high-quality females should produce a higher proportion of male than female offspring given certain assumptions. We studied relationships among age, maternal condition, and sex ratio of progeny in the collared peccary (Pecari tajacu), a sexually monomorphic ungulate, in southern Texas to examine this hypothesis. We collected data on litter size and sex ratio from 264 peccaries from 1989 to 2003. The overall fetal sex ratio was male-biased (P = 0.04) at 54.8% male. Sex ratio varied by age, with individuals in age class 2 (of 4) being responsible for most of the skew in the ratio. Condition indices (body mass, carcass mass, and kidney fat index) did not vary in females categorized by sex ratio of litters. Logistic regression revealed that increasing condition of peccaries was associated with a more male-biased litter, but these relationships were weak (P = 0.10–0.20). Our results were consistent with recent work showing sex ratio–age relationships and reviews documenting decreasing support for the Trivers–Willard hypothesis in ungulates with less sexual dimorphism.

Translocation is a common tool for restoring wildlife populations; however, potential genetic consequences include reduced levels of diversity within and increased divergence among populations. Elk (Cervus elaphus) were extirpated across much of North America by the early 20th century, but subsequent translocation programs restored the species to much of its historic range. The effects of these reintroductions on current patterns of genetic diversity in the western United States are largely unknown. We predicted that populations initiated with few founders and those experiencing slow postreintroduction growth would exhibit lower levels of diversity than other reintroduced populations. We used 12 microsatellite markers to examine patterns of genetic variability across 5 reintroduced populations of elk and 2 source herds from the Greater Yellowstone Ecosystem. The northern and southern Yellowstone source herds, which migrate to wintering areas separated by more than 260 km, exhibited similar levels of genetic diversity and high levels of gene flow, identified through both direct (i.e., assignment tests) and indirect measures. Levels of genetic diversity also were relatively high in all populations (unbiased heterozygosity, H_E = 0.51–0.60; allelic richness based on a sample size of 21, AR₂₁ = 3.3–4.0) and did not differ significantly between source and reintroduced populations or among reintroduced populations. We observed low to moderate levels of differentiation (Weir and Cockerham's F_ST statistic, θ = 0.01–0.08) and small genetic distances (Nei's standard genetic distance, D_S = 0.02–0.11) between populations. The relatively high levels of genetic diversity and low differentiation observed among our sampled populations are in stark contrast to observations of low diversity and high differentiation among isolated reintroduced populations of elk in the eastern United States. These results suggest that gene flow that includes other elk populations in the western United States may aid in preserving genetic diversity and limiting genetic divergence.

Parturient ungulates are relatively more sensitive to predation risk than other individuals and during other times of the year. Selection of calving areas by ungulates may be ultimately related to trade-offs between minimizing risk of predation and meeting nutritional needs for lactation. We used digital and field data to examine selection of calving areas by 31 global positioning system–collared moose (Alces alces) in southeastern British Columbia. We examined movements 12 days before and after calving, and analyzed habitat selection at 2 scales of comparison: the immediate calving area to the extended calving area (100 ha), and the extended calving area to the surrounding home range. Maternal moose exhibited 1 of 2 distinct elevational strategies for calving area selection during the days leading up to calving: 16 moose were climbers and 15 were nonclimbers. Climbers moved a mean of 310 m higher in elevation to calve, whereas nonclimbers showed little change in elevation. Hourly movements by all maternal females increased 2- to 3-fold in the 1–4 days before calving and were generally directional, such that all calving areas were outside of areas used during the 12 days before calving. At the broad scale, elevation was the strongest predictor of the extended calving area within the home range. At the fine scale, climbers selected areas with reduced tree density, reduced forage, and increased distance from water, whereas nonclimbers selected areas with increased forage, decreased distance from water, and decreased slope. Beyond the obvious elevation difference between climbers and nonclimbers, moose appeared to exhibit 2 distinct calving strategies in mountainous ecosystems. A functional explanation for the 2 strategies may be that climbers moved into areas where forage quantity and quality were relatively low, but where risk of predation (mainly by grizzly bears [Ursus arctos]) also was reduced. Nonclimber moose calved in areas with higher forage values, and appeared to select areas at the finer scale to reduce predation risk (e.g., association with water and reduced tree density for visibility).

We examined daytime movements of a herd of African elephants (Loxodonta africana) at 10-min, 15-min, and 20-min intervals in Pongola Game Reserve, South Africa. This group tended to proceed in a consistent direction during consecutive movements, especially during long moves. Serial movement lengths and serial movement angles were autocorrelated at 10-min and 15-min intervals but not at 20-min intervals, indicating that 20-min intervals may be a suitable temporal scale to avoid oversampling. Herd movements followed a Lévy-modulated correlated random walk. In addition, looping movements were detected. Spatial scale of the loops averaged about 1 km. Movement strategies that include both Lévy walks and correlated random walks are thought to optimize foraging.

The diet of the Brazilian slender opossum (Marmosops paulensis) was determined through analysis of fecal samples collected in an area of montane Atlantic forest in southeastern Brazil. M. paulensis consumed insects, arachnids, gastropods, fruits, flower parts, and small vertebrates. The observed preference for Piper fruits could be related to the spatiotemporal predictability of this item, whereas the observed preference for the Coleoptera, the Blattodea, and the Opiliones could be due to overestimation of hard-bodied prey. Diet composition varied seasonally, with invertebrates and flower parts being consumed more during the dry season, probably because of their higher relative abundance when compared to fruits in this season. Diet was more diverse during the dry season, because of the inclusion of new fruit species and the reduced contribution of Piper fruits in the diet. We suggest that M. paulensis is more frugivorous than previously thought and that this species can be an important seed disperser of pioneer plants, especially of Piper species.

Ecological physiology examines how animals cope with changing environmental demands. In low-productivity desert habitats, small mammals should consume low-quality, high-fiber food as a consequence of necessity rather than by choice. Diet quality of populations can differ at both spatial and temporal scales. Nevertheless, spatial and temporal variation in the digestive system has not been extensively studied in the field. We captured individuals from 4 populations of Microcavia australis and measured their digestive morphological traits. Fieldwork was carried out in 4 localities belonging to arid and semiarid regions, in dry and wet seasons. We also estimated diet quality for each population and season. We found significant effects of sex, season, and site on the size of digestive organs. The concentration of fiber and nitrogen in the plants consumed differed between populations and varied seasonally: dietary fiber was higher in the dry season and nitrogen concentration was higher in the wet season. As predicted by theory, the cecum, the organ most closely related to cellulose fermentation, was significantly larger in animals facing the lowest quality diet. The other organs also were affected by reproductive state and water requirements. Intraspecific variation in the digestive morphology of M. australis probably helps this species cope with remarkable seasonal and geographical variability.

Predation by feral cats (Felis catus) is recognized as a major threat to native fauna worldwide, but the competitive effects of cats on native species have not been extensively studied. Cats occur on San Clemente Island, California, in sympatry with endemic island foxes (Urocyon littoralis clementae). We examined diets of cats and island foxes between years, seasons, and habitats to assess the potential for resource competition between the 2 species. Analysis of 602 cat and 958 fox feces revealed a high level of dietary overlap (O = 0.93) and relatively narrow niche breadths for both species (B_{standard Fox} = 0.37; B_{standard Cat} = 0.49). Despite the overlap in diet, cats and foxes appear to partition prey resources. Cats consume approximately equal proportions of arthropod (47.9%) and vertebrate (44.2%) prey, the latter primarily rodents (29.2%) and lizards (12.9%). In contrast, foxes appear to rely more on arthropods (57.7%), with plants (20.5%) and vertebrates (21.6%) occurring in lower, but roughly equal frequencies. Season appeared to have little effect on diet; however, diet did vary between habitats and years for both species. Diets of cats on San Clemente Island are consistent with those from other studies. We found no evidence of a dietary shift by foxes that were in sympatry with cats.

In mammalian predators, prey size typically increases with body size, such that most carnivores weighing >21.5 kg specialize on prey weighing ≥45% of their own mass. By hunting in packs, endangered African wild dogs (Lycaon pictus) are able to feed primarily on ungulates weighing >100% of their own individual mass and, in most populations, wild dogs specialize on such large prey. However, we show that wild dogs living outside protected areas in northern Kenya fed primarily on Kirk's dikdiks (Madoqua kirkii), small antelope weighing just 15% of wild dog body mass. We estimated that dikdiks constituted 70% of the prey biomass consumed by wild dogs. Despite feeding on small prey, pack size, home-range size, and vital rates in this population were similar to those recorded in protected areas where wild dogs specialize on much larger ungulates. The energy content of a dikdik was about one-tenth that of the 2nd most important prey, impala (Aepyceros melampus). However, because dikdiks occurred at high population densities, the 2 prey species had apparently comparable hunting profitabilities. Wild dog packs ate more small (<10-kg) prey when confined to a breeding den. Also, packs living on commercial ranches consumed fewer small prey than did those living on community lands where larger prey were depleted. However, demographic parameters were similar in the 2 land uses. Although livestock occupy virtually the whole area, wild prey have persisted because local Masai and Samburu pastoralists do not traditionally hunt wild ungulates. This tradition has helped wild dogs to recolonize successfully and to reach densities comparable with those recorded in protected areas. The apparent ability of wild dogs to persist on small prey, in a livestock-dominated ecosystem, suggests that other important populations might occur, or be recoverable, in Africa's unprotected rangelands.

Shrub encroachment as a result of heavy grazing is assumed to affect species diversity negatively. However, shrubs may be important for animals because they provide shelter and nesting sites. In this study we analyzed the importance of shrubs as habitat structures at 3 spatial scales for yellow mongooses (Cynictis penicillata) in southern Kalahari rangelands. At burrow location we assumed shrubs reduce predation risk for occupants of burrows under shrubs and that shrubs protect burrows from trampling by larger herbivores. To investigate this, at microhabitat scale, we recorded the location of 24 reproductive and 112 sheltering burrows. However, in shrub-encroached areas prey availability is low. We surveyed vegetation cover and the spatial distribution of shrubs at mesoscale (1 ha) and compared it to random surveys. Group size and reproductive success were determined for 18 groups and related to shrub cover at territory scale (macroscale, 250 ha). Our results show that yellow mongooses prefer reproductive burrows under large Acacia shrubs if the distance to the next shrub was greater than 10 m. At mesoscale, areas with lower vegetation cover were favored. Shrub encroachment at territory scale (macroscale) affected group size negatively. A range of shrub cover between 15% and 17.5% indicates a critical upper threshold limiting reproduction. For yellow mongooses territory selection represents a trade-off between abundance of suitable shrubs for burrows (protection service) and the proportion of shrub cover at large spatial scales (reduced prey availability).

In addition to the role of latrine sites as areas for deposition of feces, they may play roles in territoriality, sexual attraction, warning and defense behaviors, and regulation of physiological functions. Several carnivores, such as the common genet (Genetta genetta) use latrines as stations for scent communication. We describe the factors influencing the placement and use of latrine sites by a Mediterranean population of common genets inhabiting cork oak woodlands in southwestern Portugal. Using logistical regression analysis, we found a higher probability of finding latrines in areas with high understory height and diversity of landscape units, low human disturbance and accessibility, and proximity to potential refuges and other latrines. An exploratory univariate analysis showed that latrines were located primarily in conspicuously high features within the landscape such as in old-growth cork oak trees. Their use was associated with low human disturbance, inaccessibility, and high understory cover. Our results suggest that forest managers should preserve some old trees in oak woodlands, because these trees have a fundamental role in scent communication among genets (latrines), as well as serve as resting sites.

Ancestrally continental forest species of the tribe Oryzomyini, the endemic cricetid rodents of the Galápagos, have had to adapt to the harsh tropical desert of the Islands. Following the recent rediscovery of the Santiago nesoryzomys (Nesoryzomys swarthi) endemic to Isla Santiago, Galápagos, we conducted the 1st autecological study of this species. Our 3-year study revealed mean annual survival of 23.2% and maximum survival of 812 days. Reproductive activity was restricted to the wet season with a stable annual proportion of breeding females and a consistent peak in pregnancy in April. The likelihood of postpartum breeding increased with rainfall when 2 litters were produced. The growth and development of juveniles was slow and they did not reproduce in their natal year. Positive correlations between rainfall and mean adult body weight and between vegetation density (particularly prickly pear cactus [Opuntia galapageia]) and population levels supported a hypothesis of food limitation. Comparisons with the Galápagos oryzomys (Oryzomys bauri), endemic to Isla Santa Fe, and a review of continental members of the tribe Oryzomyini suggest that the ephemeral, unpredictable environment of the Galápagos arid zone has selected for a strategy of relatively high survival and low reproduction in N. swarthi and O. bauri that is more typically found among the desert Heteromyidae than other members of the Oryzomyini. We also present data on sex ratio, home range, and philopatry that together indicate a promiscuous or polygynous mating system. Our findings may help to guide future conservation strategies for this endangered rodent species.

Red squirrels (Tamiasciurus) are hypothesized to be coevolving with pinecones (Pinus), whereby squirrel seed predation selects upon cone serotiny and seed number, which in turn select upon squirrel size and strength. I tested the hypothesis that cone morphology produces phenotypic size differentiation in red squirrels (T. hudsonicus). I measured body mass, hind-foot length, and jaw width of squirrels among spruce (smaller soft cones), lodgepole pine (larger serotinous cones), and mixed conifer (both cone types) habitats while controlling for variability in geographic isolation and latitude. I found identical average values among habitats for all body measurements: larger squirrels were not associated with larger tougher cones. Geographic isolation or a latitudinal gradient appear necessary to promote size differentiation in red squirrels, but how these factors interact with habitat (cone morphology) remains to be documented. As such, whether squirrels and pinecones actually are coevolving largely remains speculation.

Little is known about nest use by flying squirrels (Glaucomys) in partially harvested forests, especially for northerly populations where cavity use is prevalent. We used radiotelemetry to examine nest use by 24 southern flying squirrels (G. volans) in 2003 in logged and unlogged hardwood forests, and by 18 northern flying squirrels (G. sabrinus) in 2004 in conifer forests, in Algonquin Provincial Park, Ontario, Canada. Of 76 nest trees used by G. volans, 71% were in declining trees and 22% were in snags. Sixty tree nests used by G. sabrinus included 28% snags, 46% declining trees, and 25% healthy trees, although nearly one-half of nests of G. sabrinus that were used on more than 3 occasions were in snags. G. volans used larger-diameter trees and American beech (Fagus grandifolia) more often than expected by chance, whereas G. sabrinus used trembling aspen (Populus tremuloides), white birch (Betula papyrifera), and yellow birch (B. alleghaniensis) more than expected by chance. Both species used a high proportion of cavity nests, few external nests, and trees that were decayed or diseased. We found indications that nest supply was limited in recently harvested sites, where there were fewer cavity trees and snags; however, G. volans may compensate by using abandoned yellow-bellied sapsucker nests and by nesting in aggregations. Hardwood snags and decaying trees appear to provide crucial nesting habitats for both squirrel species, particularly for females.

Activity patterns of many nocturnal mammals are synchronized to daily cycles of light and dark. Light intensity is an important cue for nocturnal mammals because of the interplay between illumination and risk from visual predators. Studies suggest that nocturnal rodents are at greater risk from visually oriented predators before full darkness than after full darkness. We examined onset of surface activity of Ord's kangaroo rat (Dipodomys ordii) over 3 seasons in central Nebraska. To determine surface activity, we used a nonobtrusive procedure—buried timers near burrows. Although initiation of aboveground activity was significantly correlated with sunset from season to season, mean onset of surface activity differed among seasons: 1 min before the start of full darkness in summer, 4 min before full darkness in autumn, and 15 min after full darkness in winter. Despite apparent costs of emerging before darkness, 61% of kangaroo rats in summer and 63% in autumn emerged before full darkness. In winter, however, only 19% of kangaroo rats began surface activity before full darkness. We suggest that emergence behaviors of nocturnal rodents from daytime shelters are plastic and probably linked to seasonal trade-offs between costs of predation and benefits of reproduction and food abundance.

Black-tailed prairie dogs (Cynomys ludovicianus) alter shortgrass-steppe landscapes in ways that are expected to affect other mammals. I sampled rodent populations at 31 sites on the Pawnee National Grasslands, Colorado, including 18 active colonies, 6 colonies that had been unoccupied for >6 years (inactive), and 7 grassland sites without prairie dogs (controls). Rodents were livetrapped for 4 consecutive nights at each site between May and August 2004 to estimate relative abundance. I also measured vegetation and habitat characteristics. Northern grasshopper mice (Onychomys leucogaster) and 13-lined ground squirrels (Spermophilus tridecemlineatus) were captured on most (≥87%) of the sites and comprised 40% and 34% of individuals captured, respectively. Species richness ranged from 1 to 6 species, but most sites had only these 2 species. Grasshopper mice tended to be more abundant on colony sites than on controls, although differences were not statistically significant. Ground squirrels were least abundant on active colonies, and most abundant on inactive colonies, followed by controls. Habitat types did not differ in their abundance of any other species or in total rodent abundance; however, active colony area influenced total rodent abundance, with small colonies supporting fewer individuals. Controls supported the most rodent species, in part because these sites consistently had taller grass, which presumably provided habitat and food for less common species (Chaetodipus hispidus, Perognathus flavus, and Reithrodontomys megalotis). In shortgrass steppe, active colonies provided habitat for grasshopper mice, which may be involved in maintenance and spread of plague, but did not support consistently higher rodent species richness than the surrounding grasslands.

We compared track-tube sampling with mark–recapture livetrapping and evaluated a track-tube index, defined as the number of track tubes with identifiable small mammal tracks during a 4-night period, as a predictor of small mammal abundance estimates in North Dakota grasslands. Meadow voles (Microtus pennsylvanicus) were the most commonly recorded species by both methods, but were underrepresented in track-tube sampling, whereas 13-lined ground squirrels (Spermophilus tridecemlineatus) and Franklin's ground squirrels (S. franklinii) were overrepresented in track-tube sampling. Estimates of average species richness were lower from track tubes than from livetrapping. Regression models revealed that the track-tube index was at best a moderately good predictor of small mammal population estimates because both the form (linear versus curvilinear) and slope of the relationship varied between years. In addition, 95% prediction intervals indicated low precision when predicting population estimates from new track-tube index observations. Track tubes required less time and expense than mark–recapture and eliminated handling of small mammals. Using track tubes along with mark–recapture in a double sampling for regression framework would have potential value when attempting to estimate abundance of small mammals over large areas.