We studied factors influencing home-range size in fluctuating populations of Microtus ochrogaster and M. pennsylvanicus in alfalfa, bluegrass, and tallgrass habitats over a 25-year period in east-central Illinois. Preferred food availability for both species was greatest in alfalfa and least in tallgrass, lesser during winter than other seasons in all 3 habitats, and greater in alfalfa during winter than in the other 2 habitats. Vegetative cover was sparse, especially during winter, in alfalfa and dense year-round in bluegrass and tallgrass. Movement distances of M. ochrogaster tended to be smaller in alfalfa than in bluegrass and tallgrass; movement distances of neither vole species differed between bluegrass and tallgrass. Within alfalfa, movement distances of both species were smaller during winter, when cover was sparse and food availability low. No seasonal difference was found in movement distances of either species within bluegrass and tallgrass, where cover was dense year-round, but food availability was low during winter. Movement distances of M. ochrogaster were not affected by supplemental feeding in bluegrass and tallgrass; those of M. pennsylvanicus were smaller in supplementally fed tallgrass. We conclude that cover, as an indicator of risk of predation, influenced home-range sizes of both species more than did food availability.

Female small mammals are often territorial. Two hypotheses explaining territoriality of females predict that females should exclude competing females from territorial boundaries. For water voles, these hypotheses allow either static territoriality, in which the geographical locations of territories remain constant, or drifting territoriality, in which the locations of territories constantly shift. If females defended entire territories over short periods, gains and losses of habitat would be actively competed for, potentially resulting in static territoriality. We attempted to discern whether water vole territories drift, and why, and whether territories at high densities are more static, by analyzing patterns of short-term and long-term range use at different population densities. Water voles were radiotracked at 2 study sites, 1 supporting a high population density and 1 supporting a low population density. Range sizes of females did not reach asymptotes with increasing observations at either site, and the geographical locations of their ranges constantly shifted via gains and losses of habitat. The degree to which territories of females shifted was larger at the low-population-density site. These range-use patterns could be partially explained by mating behavior in which males and females interacted closely for extended periods, potentially leaving areas of the females' territories undefended. We conclude that female water voles exhibit drifting territoriality, that this may partially result from inherent flexibility in their territories due to mating behavior, and that the degree to which territories drifted was smaller at higher density.

The behavior of prey individuals is influenced by a variety of factors including, but not limited to, habitat configuration, risk of predation, and availability of resources, and these habitat-dependent factors may have interactive effects. We studied the responses of mice to an increase in perceived predation risk in a patchy environment to understand how habitat corridors might affect interactions among species in a fragmented landscape. We used a replicated experiment to investigate corridor-mediated prey responses to predator cues in a network of open habitat patches surrounded by a matrix of planted pine forest. Some of the patches were connected by corridors. We used mark–recapture techniques and foraging trays to monitor the movement, behavior, and abundance of small mammals. Predation threat was manipulated in one-half of the replicates by applying an olfactory predator cue. Corridors synchronized small mammal foraging activity among connected patches. Foraging also was inhibited in the presence of an olfactory predator cue but apparently increased in adjacent connected patches. Small mammal abundance did not change as a result of the predator manipulation and was not influenced by the presence of corridors. This study is among the 1st to indicate combined effects of landscape configuration and predation risk on prey behavior. These changes in prey behavior may, in turn, have cascading effects on community dynamics where corridors and differential predation risk influence movement and patch use.

We studied patterns of and factors influencing abundance of hispid cotton rats (Sigmodon hispidus) in tallgrass prairie habitats from autumn 1981 to spring 2001 at the Konza Prairie Biological Station, Kansas. Abundance of cotton rats was low during autumn (X̄ = 0.57 individuals/trapline) and extremely low in spring (X̄ = 0.04 individuals/trapline). Autumn abundance varied widely in 20 years (range: 0.00–2.50 individuals/trapline) and among 14 sites (0.05–1.35 individuals/trapline). Spring prairie fires had a positive influence on cotton rats during the 1st (X̄ = 0.8 individuals/trapline) and 2nd autumns (X̄ = 1.0 individuals/trapline), but not during the 3rd or later autumns (X̄ = 0.2 individuals/trapline). Cotton rats were associated strongly with lowland prairie relative to breaks and upland prairie. Autumn abundance was correlated positively with previous winter (December–February) average maximum temperature, but was not correlated with previous winter precipitation, summer (June–August) average maximum temperature, summer precipitation, or aboveground net primary productivity. Although previous winter maximum temperature accounted for only 32% of interautumn variation in abundance, winter harshness appears to be the major factor driving temporal variation in autumn abundance of hispid cotton rats.

We investigated the effects of food availability, fire, and habitat structure on population rates of increase of the rodent Bolomys lasiurus in forty 4-ha plots distributed over an area of about 200 km² in Amazonian savannas near Alter do Chão, Pará, Brazil. Mean rodent density over the entire study area declined by about one-half during the study period, despite largely independent density fluctuations within plots. Fires had no detectable association with density and population growth rates. Both densities and population growth rates were significantly associated with availability of invertebrate prey and a multivariate index of habitat structure. Invertebrate availability varied temporally within plots, and was not predictable from knowledge of vegetation structure or fire events.

Habitat use of quokka (Setonix brachyurus) in the northern jarrah forest of Western Australia was determined by monitoring movements of 58 quokkas over 2 years in 5 local populations. Quokkas were largely restricted to Agonis swamps that occur patchily throughout the jarrah forest. Within swamps, they are habitat specialists, preferring early seral stages that have been burned within the previous 10 years. This preference derives from a combination of dietary requirements and refuge from predation. As swamps mature they become suboptimal, forcing quokkas to colonize new patches. Since the collapse of the metapopulation following the introduction of the European red fox (Vulpes vulpes) in the 1930s, quokkas have been forced to remain at a site because predation inhibits dispersal.

In the Simpson Desert, central Australia, heavy rainfalls associated with the La Niña phase of the El Niño Southern Oscillation (ENSO) during 1999–2000 stimulated a pulse of primary productivity that prompted a rodent irruption during 2001, and subsequently an extensive wildfire in 2001–2002. More than 10,000 km² of spinifex habitat were burned. In this study we examine a time series of climatic variables, and small mammal and predator dynamics in the desert in 1999–2002; and a before–after–control-impact study investigating the effects of the wildfire on small mammals. Rodents showed a delayed numerical increase in response to rainfall, whereas terrestrial predators showed a delayed numerical increase in response to rodent density. These delayed responses suggest the existence of bottom-up trophic pathways. However, a reduction in primary productivity and increase in predators appeared to suppress rodent numbers in 2001–2002, indicating that bottom-up effects can be temporarily reversed in this system. Wildfire had negative impacts on the abundance of the desert mouse (Pseudomys desertor) and the overall richness of small mammal species. Several other species of small mammals also appeared to show brief negative responses to wildfire. The impacts of wildfire on small mammals appear attributable to a loss of habitat for spinifex-dependent species and increased exposure to predation in burned habitats. Because extensive wildfires can be predicted from patterns of rainfall and fuel accumulation, we recommend that land managers be proactive in recognizing and reducing conditions of fire hazard. We recommend that small-scale prescribed burns should be carried out to reduce the extent of wildfires and also increase the chance of maintaining potential refuges from predators. In addition, control of introduced predators during and after irruptions of rodents will be crucial to prevent predator-driven crashes of their populations and those of secondary prey species. ENSO-related climatic forecasts appear to be useful cues that can be incorporated into fire and predator management strategies in arid Australia.

Diets of mammals are increasingly being inferred from identification of hard parts from prey eaten and recovered in fecal remains (scats). Frequencies with which particular prey species occur among collections of scats are easily compiled to describe the average diet, and can be used to compare diets between and within geographic regions, and across years and seasons. Important to these analyses is the question of statistical power. In other words, how many scats should be collected to compare the diet among and between species? We addressed this problem by using Monte Carlo simulations and frequency of occurrence methods to analytically determine the consequence of sample size on the dietary analysis of scats. We considered 2 questions. First, how is the statistical power affected by sample size? Second, what is the likelihood of not identifying a prey species? We randomly sampled predetermined numbers of scats (n = 10–200) from computer-generated populations of scats containing prey of known species and frequencies of occurrences. We also randomly sampled a large database of field-collected scats from Steller sea lions (Eumetopias jubatus). We then used standard contingency table tests such as chi-square and Fisher's exact test to determine whether differences between our samples and populations were statistically significant. We found that a minimum size of 59 scats is necessary to identify principal prey remains occurring in >5% of scats. However, 94 samples are required when comparing diets to distinguish moderate effect sizes over time or between areas. These findings have significant implications for the interpretation of published dietary data, as well as for the design of future scat-based dietary studies for pinnipeds and other species.

We captured 11 Myotis sodalis and radiotracked them to foraging areas near Indianapolis International Airport during summer 2002. A series (3–7) of multiazimuth triangulations was used to obtain an estimate of the location of each bat throughout the night. Compositional analysis was used to compare habitat that bats used to available habitat at 2 spatial scales. At both spatial scales, bats preferentially used woodlands over other available habitats (especially developed habitats). These findings suggest that suburban development may negatively impact M. sodalis by limiting foraging options. Many conservation plans aimed at protecting bats exclusively target roosting sites. Although roost conservation should continue to be central in efforts to protect bats, available foraging habitat also should be considered.

The endemic and endangered golden-crowned flying fox (Acerodon jubatus) coroosts with the much more common and widespread giant Philippine fruit bat (Pteropus vampyrus lanensis) in lowland dipterocarp forests throughout the Philippine Islands. The number of these mixed-roost colonies and the populations of flying foxes in them have declined dramatically in the last century. We used fecal analysis, interviews of bat hunters, and personal observations to describe the dietary habits of both bat species at one of the largest mixed roosts remaining, near Subic Bay, west-central Luzon. Dietary items were deemed “important” if used consistently on a seasonal basis or throughout the year, ubiquitously throughout the population, and if they were of clear nutritional value. Of the 771 droppings examined over a 2.5-year period (1998–2000), seeds from Ficus were predominant in the droppings of both species and met these criteria, particularly hemiepiphytic species (41% of droppings of A. jubatus) and Ficus variegata (34% of droppings of P. v. lanensis and 22% of droppings of A. jubatus). Information from bat hunter interviews expanded our knowledge of the dietary habits of both bat species, and corroborated the fecal analyses and personal observations. Results from this study suggest that A. jubatus is a forest obligate, foraging on fruits and leaves from plant species restricted to lowland, mature natural forests, particularly using a small subset of hemiepiphytic and other Ficus species throughout the year. In contrast, P. v. lanensis has a broader diet, including fruits, leaves, and flowers; forages in both natural and agroforests; and uses a wider variety of fruit than does A. jubatus in natural forest habitats. A small subset of the available Ficus species also is used heavily by P. v. lanensis throughout the year. These results provide insight into the autecology and interspecific relationship of these coroosting species, as well as suggest the prospects of both species' continued survival given changes in their habitat.

We evaluated hypotheses that the positions of day-roosting bats on the undersurface of bridges were governed by considerations related to predator avoidance and thermoregulation. From January 2002 to January 2003, we characterized bridge roosts in the Kisatchie National Forest located in north-central Louisiana, United States. Bats, predominately Corynorhinus rafinesquii, Pipistrellus subflavus, and Eptesicus fuscus, tended to roost in the darkest portions of the bridge and in the narrowest available spaces. They also roosted closer to the abutment, farther from the side edge, and closer to the ground than predicted; however, bats were never found roosting less than 0.4 m off the ground or against the abutments. Roost sites were warmer than other parts of the bridge and this difference was greatest in warm months. The small difference in temperatures between roost sites and other portions of the bridge is not consistent with predictions that day-roosting bats would choose the coolest possible locations. Tendency of actual roost sites to be slightly warmer than potential roost sites is best explained by the correlation of temperature with distance from the edge of the bridge. Our observations are most consistent with the hypothesis that bats roosted in areas that minimized their visibility and accessibility to predators.

We tracked 12 mule deer (Odocoileus hemionus hemionus) between February 1999 and April 2003 by using global positioning system (GPS) radiotelemetry in southeastern British Columbia to provide detailed information on migration and habitat use to local managers. We tested winter resource selection at the home-range and within-home-range scale to test a hypothesis that ungulate resource selection is scale-dependent. All sampled mule deer in this population migrated from low-elevation winter ranges to high-elevation summer ranges, supporting a hypothesis that migration is obligatory in mountainous, heavy-snow areas. We found little consistent selection at the within-home-range scale, but considerable selection at the home-range scale, supporting a scale-dependent hypothesis. Potential mule deer winter range could be predicted from 2 biophysical attributes, elevation and solar duration. Currently suitable winter habitat can then be further delineated on the basis of amount of mature coniferous forest within this zone. Use of GPS radiotelemetry increased sample intensity of individual deer, and thereby accuracy of individual parameter estimates. However, because of high equipment costs and failure rates, increased sample intensity occurred at the expense of sample size, and therefore illustrates a trade-off consideration for future work.

Microbes interfere with the olfactory communication of animals by degrading chemical signals or by adding volatile metabolites. We report on the composition and diversity of the microflora in a sexually selected scent organ, the wing sacs of Saccopteryx bilineata, which are used by males for courting females. Wing sacs lack any glandular tissues. Instead, males clean and refill their wing sacs each day with genital and gular secretions. Females have only a nonfunctional rudiment of this organ. We isolated a total of 40 microbial species with only a moderate overlap in species composition between the sexes. The estimated microbial diversity was significantly lower in males than in females, with a minimum of 52.5 microbial species ± 5.0 SD in wing sac rudiments of females and 40.3 ± 4.2 SD in wing sacs of males (jackknife estimates). Males carried on average only 2 out of 40 possible microbial species in their wing sacs. Thus, individual scent profiles of males could originate from individual microflora. The daily routine of wing sac cleaning and refilling has possibly evolved to control microbial scent degradation, to support an individual microflora involved via volatile metabolites in mate choice, or both. Microbes may play a more prominent role in the evolution of morphological structures and behavioral adaptations than previously envisaged.

Home-range size and shape are influenced by cost–benefit relationships associated with acquiring resources. Subterranean animals may be particularly affected by food availability and soil conditions because of the close coupling of their activity to soil and the high energetic expense of digging. We examined foraging tunnel length, area, and geometry (e.g., number of branches and turning angles) of 3 species of pocket gophers (Geomys attwateri, Geomys bursarius, and Thomomys bottae) in their natural habitats, which differed in food abundance and soil characteristics. Burrow features (except length and area) were similar among species, sexes, ages, and habitats. However, burrows of adults were longer and occupied larger areas than those of juveniles, and burrow system length and area decreased with increasing vegetation biomass and with increasing soil clay content of soil (i.e., increasing expense of digging). Our findings reveal common patterns of burrow geometry, which suggest that there may be an underlying strategy defining geometric features of burrows within this family of subterranean rodents.

Species that occupy the same area and use the same resources must either compete with each other or find ways to minimize competition. For rodents, 1 important resource is nesting sites. In this study I present data from direct behavioral observations in the succulent karoo of South Africa that show aggressive interactions between bush karoo rats (Otomys unisulcatus) and striped mice (Rhabdomys pumilio). Because both species nest in shrubs, the potential exists for interspecific competition for nesting sites. Because of a severe drought in 2003, the bush karoo rat became locally extirpated. As a result, striped mice nested significantly more often in shrubs that contained bush karoo rat nests than in 2001 and 2002, when the population density of bush karoo rats was high. Furthermore, I observed that striped mice never nested in the shrub Lycium cinerum, the favorite nesting site of bush karoo rats, when bush karoo rats were present, but regularly used these nesting sites after bush karoo rats became extirpated. I conclude that striped mice and bush karoo rats compete actively for access to preferred nesting sites in the succulent karoo.

Small mammals usually produce large litters of altricial young, resulting in high reproductive rates. In contrast, cavies give birth to few precocial young after a long gestation. The price of this reproductive strategy is a low intrinsic rate of natural increase. We investigated if the patterns of reproduction in a wild population of Cavia magna are consistent with the hypotheses that cavies can increase their reproductive output by breeding aseasonally and by maturing extremely early. We collected data on reproduction and growth by capture–recapture during a 26-month field study in a wetland in Uruguay, and from a laboratory population founded with individuals from the same region. Among the Caviinae, C. magna is particularly precocial, with individual neonates weighing on average 18% of maternal mass. Reproduction was mostly seasonal, with the main birth season starting at the end of September (austral spring) and extending until May in 1999 and February in 2000, respectively, with only a few females reproducing during the 1st but not the 2nd austral winter. Individual females produced on average 3 litters per year. Some females born in early spring conceived successfully between the age of 30 and 45 days, similar to females in the laboratory. The remainder of the 1st spring cohort and females of subsequent birth cohorts delayed reproduction until the following spring. Body condition and growth rates were highest in the spring, declined through the year, and varied between years, and may be the proximate factors determining whether an adult female or a juvenile initiates breeding. Breeding opportunistically whenever conditions allow might partly compensate for the low reproductive rate of cavies.

Morphometric data sets are often phenetically analyzed by using various kinds of spatial, metric, or nonmetric multivariate analyses. Such methods produce results that are difficult to compare directly with molecular or morphological phylogenetic hypotheses, which are usually expressed by using nonspatial tree representations. Therefore, it is useful in a comparative approach to analyze, and above all to visualize, morphometric pairwise relationships as tree structures. For this purpose, several additive or ultrametric methods exist, which often return different topologies for the same data set. Objective criteria are thus needed to identify the tree-building algorithm (or algorithm family) best adapted to the nature and structure of the hierarchical signal under study. Here, we present our 4-step analysis protocol that allows the construction of a morphometric tree, statistically tested for confidence, to perform direct comparisons with a phylogenetic hypothesis. As an example, we apply this protocol to the analysis of an original morphometric data set (geometric 3-dimensional Procrustes analysis of skull morphology) involving 7 species of Callithrichinae, and then compare the resulting tree to a published molecular phylogenetic hypothesis. Differences between the 2 compared trees are qualitatively and quantitatively described, and are interpreted as the result of morphological convergences due to environmental conditions, and especially to morphofunctional constraints linked to diet.

The endangered Sonoran pronghorn (Antilocapra americana sonoriensis) consists of only 2 small populations, 1 in Arizona and 1 in Mexico. Mitochondrial DNA sequence data and 5 microsatellite loci were used to compare levels of genetic diversity and differentiation between the 2 Sonoran pronghorn populations and between this subspecies and other selected pronghorn populations, both proximate and distant to the Sonoran pronghorn's current range. The data support a history of recent isolation of Sonoran pronghorn populations from those in Arizona, New Mexico, and Texas. Loss of genetic diversity due to bottlenecks and drift has been severe in both populations of the Sonoran pronghorn, but is most pronounced in the Arizona population. These results are discussed in terms of conservation management strategies.

The Patagonian opossum, Lestodelphys halli, is known from a few skeletons of captured animals and several isolated fragments recovered from owl pellets in Argentina. Recently, more than 300 remains (mandibles, maxillae, crania, and other bones) were found in owl pellets and associated bones, comprising the largest known collection of L. halli. A detailed morphological analysis of craniomandibular and dental variation is reported and comparisons with other small didelphids also are made. Intraspecific variation is discussed and differential diagnosis of the species is presented.

Since the description of Peromyscus leucopus easti Paradiso, 1960, scant work has been directed toward examining the evolutionary relationships of P. leucopus in the mid-Atlantic region. We used morphometric and molecular analyses to examine the phylogenetic relationships of 3 subspecies known from the eastern United States (P. l. easti, P. l. leucopus, and P. l. noveboracensis); additional specimens from North and South Dakota (P. l. aridulus) were incorporated in the molecular analysis. Morphometric analyses revealed that large mice are found in New England and the Appalachian Mountains as far south as west-central North Carolina and that intermediate-sized mice inhabit the Cumberland Plateau and the lowlands from Virginia southward at least to Alabama. These groups represent P. l. noveboracensis and P. l. leucopus, respectively. The smallest specimens, which are referable to P. l. easti, were found in the vicinity of Princess Anne County, Virginia. The largest mice were found on the southern half of Hatteras Island, North Carolina. Examination of D-loop sequence data revealed that there is no apparent restriction of gene flow among P. leucopus on the mainland of the eastern United States, including those from Princess Anne County, Virginia. However, mice from the southern end of Hatteras Island, North Carolina, were as distinct from specimens from the eastern United States as were mice from North and South Dakota. The population of white-footed mice from Hatteras Island, North Carolina, represents an undescribed subspecies.

Peromyscus slevini Mailliard (1924) is endemic to Santa Catalina Island, a small oceanic island in the southern Sea of Cortez. The species has been variously associated, formally or informally, with 2 subgenera—Haplomylomys and Peromyscus—and 5 species-groups—californicus, eremicus, maniculatus, and boylii or mexicanus. Based upon our taxonomic evaluations, we document that 2 species of Peromyscus, P. slevini and P. fraterculus, occur among the samples that authors have identified as P. slevini, clarify the diagnosis of P. slevini proper and allocate it to membership in the P. melanophrys species-group, and discuss biogeographic implications of this proposed relationship.

The Perognathus longimembris species group currently consists of 3 species and approximately 23 subspecies. Members of this species group have been of considerable interest to biologists in both physiological and ecological studies, and several members are threatened with extinction. No one has yet attempted a phylogenetic study including several populations from each of these 3 species to test the monophyly of these taxa and to elucidate the relationships among the species and subspecies. Mitochondrial DNA sequences from the cytochrome-b gene were used to assess the genetic variation among these species and to make a 1st approximation of the number of species that should be recognized taxonomically in this species group. Results indicate that the Arizona pocket mouse, P. amplus, and the San Joaquin pocket mouse, P. inornatus, are monophyletic entities, and should remain as single polytypic species, whereas the little pocket mouse, P. longimembris, is paraphyletic in the maximum-likelihood and maximum-parsimony phylogenies, suggesting that it might best be split into 2 polytypic species.

The greater long-tailed hamster (Cricetulus triton) is widely distributed in the farmlands of northern China. By using DNA sequence data from the mitochondrial D-loop region, we examined genetic diversity and genetic differentiation of 3 mountain populations of the greater long-tailed hamsters in 2 river drainages and 4 plain populations in the North China Plain. Phylogenetic analyses with parsimony and Bayesian inference, nested clade analysis, and analysis of molecular variance were used. The results showed that each population was significantly differentiated from others and the species possessed a high level of phylogeographic structure. The haplotypes were grouped into 2 clades that corresponded to 2 distinct topographic ranges: the mountain and the plain region. The split between the 2 clades accounted for 24% of the genetic variance observed among the examined samples. This study indicated that contiguous mountains played a potential role in genetic differentiation of the greater long-tailed hamsters in the North China Plain. It is suggested that limited gene flow among mountain populations or between mountain and plain populations, plus the impact of inbreeding or genetic drift on the small and isolated populations, accelerated genetic differentiation of mountain populations from plain populations of the greater long-tailed hamsters.

Genetic relationships were examined among wild-caught southern flying squirrels (Glaucomys volans) sharing the same natural nest cavity. Under natural conditions, typically 75–80% of southern flying squirrel nest groups comprise adult-aged individuals. The remainder nest in family-based groups or are solitary. The coefficient of relatedness within nest groups of adult individuals and family-based nest groups was examined through microsatellite DNA analysis. Family or adult nest groups were identified from the age class of individual group members determined through a discriminant function analysis based on body mass. From this information, nest groups were categorized as family-based groups comprising a single adult female with nestlings, adult groups comprising adult aged-individuals, or subadult nest groups. The average coefficient of relatedness was determined in each nest group. Within the putative family groups, most individuals were 1st-order relatives. In the adult nest groups, the coefficient of relatedness was low, indicating that these individuals were unrelated. The relationships within the subadult nest groups were intermediate. This is the 1st study to show that adult nestmate southern flying squirrels typically are unrelated and do not nest in family-based groups.