Food items consumed by sympatric maned wolves (Chrysocyon brachyurus), crab-eating foxes (Cerdocyon thous), and hoary foxes (Lycalopex vetulus) were investigated in the Cerrado of central Brazil to determine overlap among their diets. Home ranges and spatial segregation among these canids were also investigated. Overlap among diets was greatest for maned wolves and crab-eating foxes, which had generalist diets, although maned wolves fed on larger prey than did crab-eating foxes. Hoary foxes were frugivore–insectivores, with Syntermes termites being the most important food item. In relation to habitat use, hoary foxes were also the most selective canid, preferring more open habitats.

I studied a population of white-nosed coatis (Nasua narica) in southeastern Arizona from 1996 to 2000 to quantify home-range size and overlap among matriarchal groups (troops) and solitary males. Home ranges of coatis averaged 13.57 km² ± 1.72 SE for troops (n = 9) and 6.11 ± 1.42 km² for solitary males (n = 7; kernel-density estimator). Sizes of home ranges and core areas did not change during the study, even though density of coatis declined by ≥60%. Home ranges of males overlapped ≤61%, home ranges of troops overlapped ≤80%, and home ranges of males overlapped those of troops ≤67%. Locations of annual home ranges and core areas shifted slightly from year to year, indicating minor range drift but no nomadism by radiocollared coatis in this population. Mortality due to predation was significantly higher in the periphery of the home range than that predicted based on the probability of occurrence.

Juvenile recruitment, growth, survival, and time to sexual maturation of rodents are all negatively affected by high densities of adults. But whether density of males, of females, or total density of adults has the greatest effect on juveniles is not known. We maintained populations of gray-tailed voles, Microtus canicaudus, in 0.2-ha enclosures with densities of 30 males, 10 females (male-biased); 20 males, 20 females (control); and 10 males, 30 females (female-biased) breeding adults. With juvenile recruitment, population densities increased to 180 voles/enclosure (700 voles/ha) in male-biased enclosures and 200 voles/enclosure (1,000 voles/ha) in control and female-biased enclosures. Recruitment, growth, and survival of either sex juvenile were not affected negatively by adult males but recruitment and time to sexual maturation of young females were negatively affected by high densities of females. Reduced juvenile recruitment was likely due to neonatal death before emergence from nest. We conclude that females have a greater negative effect on juvenile recruitment and reproductive development than do males. This difference was slight, however, and under normal densities of wild populations probably has minimal impact on vole demography.

Long-term studies of demography and movements are rare but critical to understanding long-lived mobile mammals like caribou (Rangifer tarandus). We studied changes in the abundance, vital rates, body size, and timing of migration of the Buchans Plateau caribou herd in Newfoundland, Canada. From the early 1960s to 2000, the population grew at 6.5%/year, although survival and recruitment indicated a declining growth rate (1.4%) by the late 1990s. The numerical increase was negatively associated with other population attributes. Rates of parturition, survival to 6 months of age, and recruitment diminished significantly. Adults exhibited substantial decreases in body size. Spring migration was significantly later and autumn migration significantly earlier. We surmise that these responses may reflect heightened density-dependent competition for summer forage.

The effects of territoriality on population density in the Japanese serow (Capricornis crispus) were investigated in Japan during 24 years, 1976–2000, on individually identified animals. Adult males and females defended intrasexual territories throughout the year. Few adults held no territory. The mean annual replacement rate of territories was 8.5% for females and 8.0% for males. The mating unit consisted of a monogamous pair (in 71.3% of units) and the polygynous unit (1 male with 2 females 25.0%; 1 male with 3 females 3.8%). The mean sex ratio (adult females : adult males) was 1:0.70. The mean ratio of adult females to offspring was 1:0.83. The population density was stable (mean ± SD; 14.2 ± 2.5/km²) through the study period. Adult density was negatively correlated with territory size in both sexes. We suggest that food availability controls adult density in the Japanese serow by influencing territory size.

We identified prey remains from 3,762 scats (feces) of Steller sea lions (Eumetopias jubatus). Scats were collected from 1990–1998 on island sites across most of the range of the United States western stock of the species. Walleye pollock (Theragra chalcogramma) and Atka mackerel (Pleurogrammus monopterygius) were the 2 most common species of prey, followed by salmonids (Oncorhynchus) and Pacific cod (Gadus macrocephalus). An additional 16 species of fish and unidentified cephalopods were considered primary in the diet, either because they occurred in >5% of scats collected across the range in winter and summer or because they consistently occurred among the top 3 prey items in particular islands or island groups. Capelin (Mallotus villosus) occurred at very low frequencies despite their predominance in the diet of Steller sea lions before the 1980s. Regions of diet similarity suggest area-specific foraging strategies, with strong seasonal patterns in consumption of most species of prey. Patterns in prey consumption and characteristics of prey indicate that Steller sea lions target prey that are densely schooled in spawning or migratory aggregations at the continental shelf or along oceanographic boundary zones. We suggest that regional diet patterns among the western stock reflect regional foraging strategies of females learned at islands near the natal rookery site.

We used reciprocal exclusions to test for indirect interactions between pocket gophers (Thomomys talpoides) and aboveground insects. Sucking insects occurred at higher densities on plants that were protected from grazing by gophers (P < 0.05), whereas chewing insects damaged plants that were browsed by gophers more than plants that were protected from gopher herbivory (P < 0.05). Pocket gophers foraged more in areas treated with insecticide (P < 0.05). These results indicate that aboveground insects and the northern pocket gopher interacted through their shared plant hosts.

Adult female Richardson's ground squirrels (Spermophilus richardsonii) spend 84% of their lifetime either sleeping underground at night during the active season or hibernating underground. To assess their use of subterranean sites, 46 females were radiocollared for periods ranging from a few days to 4.5 years. Adult females typically slept in 6–11 different chambers throughout the 15-week active season and used a single site for the 37-week hibernation season. For the 1st half of the active season, which encompassed mating, pregnancy, and lactation, squirrels usually slept in 5–6 different chambers, with each sleep site generally used once for a prolonged period of consecutive nights. In contrast, in the latter half of the active season, females moved back and forth between 5–6 sleep sites. For both females that did and did not wean a litter, this switch in sleep-site usage occurred abruptly, about 40 days before entry into hibernation. Females always slept in the future parturition chamber for some or all of gestation, and they always continued to sleep in the parturition site for some or all of lactation. In contrast, adult females never slept in the future hibernation site on any night during the preceding active season. Only 50% of the females used the hibernaculum for sleeping after hibernation, and then only for 1–5 nights. The marked contrast in prior usage of the parturition site and hibernation site indicates that the hibernaculum chamber of adult female Richardson's ground squirrels is dedicated to the forthcoming hibernation period, whereas the parturition site is a multipurpose chamber used for sleeping during gestation, for parturition, and for sleeping and litter rearing during lactation.

Golden-mantled ground squirrels (Spermophilus lateralis) in the laboratory are most likely to enter torpor when the linoleic acid content of their diet is 33–62 mg/g diet. Diets of free-ranging ground squirrels vary in linoleic acid content throughout summer; however, they often do not have constant linoleic acid content for more than a month. The influence of natural short-term (<1 month) changes in diet levels of polyunsaturated fatty acid (PUFA) on hibernation could not be predicted by previous studies because they involved subjects maintained on diets with the same PUFA content for 7–24 weeks. Hibernation experiments with laboratory feeding were conducted on S. lateralis to determine the influence on torpor of short-term (<1 month) shifts in diet PUFA levels. Reducing diet linoleic acid content for just 19 days immediately before onset of hibernation enhanced torpor of S. lateralis that ingested diets with high–linoleic acid (>62 mg/g) levels during early-summer feeding. But increasing diet linoleic acid levels for 19 days did not increase torpor of squirrels fed diets with low–linoleic acid (<33 mg/g) content during early-summer feeding. Short-term changes in diet PUFA content can thus have a strong influence on hibernation ability and overwinter survival in some circumstances.

This study, conducted on female black bears from 3 study areas in the Rocky Mountains, showed that pregnant females in a state of diapause during early winter had about 89% larger fat depots than did nonreproductive females going into hibernation. Fat provided 92% of the total energy for lactation and gestation. Rates of fat loss (g/day) were 37% greater and protein loss about 2.4 times higher for reproductive females than for nonreproductive females. The cost of winter reproduction, including gestation and lactation, was 1,432 kJ/day to produce 2 young. Although reproduction required elevated protein breakdown, rates of overall protein loss were relatively small, perhaps due to a short period of implantation and an extraordinary ability to hydrolyze urea.

We investigated reproductive characteristics of brown bears (Ursus arctos yesoensis) in the Oshima Peninsula, Hokkaido, Japan, based on the study of individuals harvested from 1983 to 1987. Analyses were based on age-class and reproductive status data determined for 196 females killed during the study period. The minimum age at 1st parturition was 4 years, but frequency of reproductive success among females <6 years old was notably lower than that among females ≥6 years of age. Females <6 years old were more apt to produce single offspring and lose them during the 1st year. There appeared to be few changes in frequency of reproducing cubs among females 6–20 years of age. Females typically separated from young when young were 15–27 months old. For mature adult females, mean litter size was 1.8, and interval between births was 2.3–3.0 years. Embryo loss and neonatal mortality were uncommon.

Several hypotheses have been advanced to explain the functions of copulatory plugs: to store spermatozoa, reduce postcopulatory leakage of semen, or prevent further matings. These hypotheses were examined in captive masked palm civets (Paguma larvata). The results showed that spermatozoa were absent in histological sections of copulatory plugs, and copulatory plugs were dislodged from the vagina during a female's 2nd copulation (time to dislodgment 10.8 min ± 1.2 SE). Time to dislodgment was significantly reduced if copulations with 2 males occurred in rapid succession (6.3 ± 2.7 min). However, some plugs were retained up to 18–22 h after 2nd copulations. Females sometimes mated with 2 partners during 1 night, and plugs of the males could be distinguished morphologically. These results suggest that the copulatory plug functions primarily to prevent leakage of spermatozoa from the reproductive tract of the female.

Twelve species (292 individuals) of small mammals were livetrapped and examined for parasitic arthropods in 17 localities in Mississippi from June through November 1998. Fifteen species of ectoparasites were collected: 2 species of sucking lice (Anoplura), 4 species of fleas (Siphonaptera), larvae of 2 species of bots (Cuterebridae), 4 species of mesostigmatid mites (Mesostigmata), and immature stages of 3 species of hard ticks (Ixodidae). The white-footed mouse (Peromyscus leucopus) harbored the most species of parasitic arthropods (8), followed by the cotton mouse (Peromyscus gossypinus—6), and the cotton rat (Sigmodon hispidus—5). New state records for Mississippi were established for the sucking louse Hoplopleura hirsuta, the bot Cuterebra americana, the laelapid mite Laelaps alaskensis, and the fleas Orchopeas pennsylvanicus and Peromyscopsylla scotti.

We describe and compare field recordings of echolocation calls of the neotropical emballonurid sac-winged bats Balantiopteryx plicata, B. io, and B. infusca. These 3 species have search-phase calls with principal energy in the 2nd harmonic, characterized by a long narrowband component followed by a short broadband component. Variation in call parameters follows only partially the scaling pattern with body size generally found in bats. Based on characteristics of their echolocation calls, we hypothesize that B. io and B. infusca forage in more cluttered habitats than does the congeneric B. plicata, which typically hunts in open areas.

Eleven polymorphic microsatellite DNA markers were screened to investigate patterns and processes of genetic variation in Allegheny woodrats at 2 spatial scales, geographically distinct populations and subpopulations within populations. The microsatellite markers detected considerable genetic variation and diversity, with an average heterozygosity of 62.0% (range 25.7–75.0%) and an average of 10.4 alleles per locus (range 5–19). Subpopulations conformed to Hardy–Weinberg expectations in 98.9% of comparisons, and allele frequency differed among subpopulations in 99.3% of comparisons. All statistical tests indicated significant genetic subdivision at the population and subpopulation levels. Theoretical estimates of gene flow were low among subpopulations, suggesting that effective dispersal is limited among subpopulations separated by as little as 3 km. A significant range-wide relationship between geographic and genetic distance at both scales suggests isolation by distance as a mechanism for the observed differentiation. The relationship between genetic distance and geographic distance among the 19 subpopulations within the central Appalachians was significant but weak. Results suggest that Allegheny woodrats associated with clusters of geographically proximate rock outcrops may function as population units. We recommend that individual rock outcrops or groups of geographically proximate outcrops be considered as population units for management.

Mitochondrial cytochrome-b DNA and karyologic data were used to clarify taxonomic status of genera Coendou and Sphiggurus within the family Erethizontidae (Rodentia: Hystricognathi). Molecular and karyologic data were concordant in demonstrating that Coendou and Sphiggurus represent 2 evolutionary lineages. Comparative analyses showed that species of Coendou are karyotypically conservative, sharing the same diploid and fundamental number, whereas those of the genus Sphiggurus diverge in diploid number despite sharing the same fundamental number. We herein describe the karyotype of Sphiggurus melanura, a species considered a junior synonym of S. insidiosus by some authors. Our karyologic data (2n = 72, fundamental number = 76), however, clearly contradict this hypothesis and suggest that S. melanura is a valid taxon.

Genic variation among representatives of Mexican lagomorphs as revealed by allozymic variation at 31 presumptive loci of Lepus californicus, L. callotis, L. flavigularis, Romerolagus diazi, and Sylvilagus floridanus, was assessed using horizontal gel electrophoresis. Results indicated that the most genically variable species is the widespread L. callotis, whereas the least variable is the endangered L. flavigularis. Genetic distances and phenograms showed that jackrabbits are highly similar to each other and that Romerolagus is genically more similar to Sylvilagus than to Lepus.

We review systematics of genus Didelphis in Venezuela by craniometrical analyses of 93 skulls from adult D. albiventris pernigra, D. a. imperfecta, and D. marsupialis. Adults were sexually invariant for most characters, although males were, in general, larger than females. Complementary morphometric data obtained from literature on D. virginiana from Mexico and D. aurita from Brazil were used for comparisons with Venezuelan taxa. Statistical analyses showed that all samples of D. marsupialis were homogeneous in skull dimensions and that D. a. imperfecta was smaller than other taxa. Size-independent analysis revealed a clear differentiation in shape between D. a. imperfecta and D. a. pernigra. Discriminant functions based on skull parameters allowed us to accurately distinguish D. a. imperfecta from D. a. pernigra and from sympatric populations of D. marsupialis. Results obtained in this study and background information suggest upgrading of D. a. imperfecta to the species level.

Cynomops (dog-faced bat) generally is regarded as either a monophyletic genus or, in some cases, a subgenus of Molossops. Species limits and phylogenetic relationships within Cynomops, however, remain unresolved due primarily to subtle morphological differences and similarity in size of the small taxa. We used a combination of morphometric analyses for quantifying size variation and molecular data for reconstructing the evolutionary history within Cynomops. Rooting the tree with Eumops hansae produced a clade of Molossops neglectus and M. temminckii that was sister to a monophyletic Cynomops clade. The most parsimonious topology (in parenthetical notation) for Cynomops was (((paranus planirostris) (greenhalli abrasus)) mexicanus). Molecular analysis supports the autapomorphy of white venter as diagnostic for C. planirostris, although there was some overlap in size with the slightly larger, dark-venter C. paranus. Cynomops greenhalli was intermediate in size between C. paranus and C. mexicanus, but molecular analyses placed it as sister to the large-sized C. abrasus. The western Mexico endemic C. mexicanus, traditionally considered a subspecies of C. greenhalli, averaged larger in size than the other small Cynomops taxa and was the most basal lineage, requiring its designation as a distinct species.

We examined sequence variation in the control region of the mitochondrial genome from 778 seals sampled at 161 locations from northern Japan to southeastern Alaska to learn more about the evolutionary history and population structure of, and effects of recent declines on genetic diversity in, harbor seals (Phoca vitulina) in the northern Pacific Ocean. High haplotypic diversity (H = 0.975) and a poorly resolved mitochondrial genome (mtDNA) phylogeny suggest that harbor seals in the Pacific underwent a rapid expansion in population size in their recent evolutionary past, possibly after the retreat of Pleistocene ice sheets. Weak phylogeographic partitioning of lineages attests to a complex evolutionary and demographic history of contemporary Pacific populations. Extensive macrogeographic subdivision was evident among a subset of grouped localities that represent centers of abundance along the distributional continuum. Heterogeneity was influenced by population size and correlated with geographic distance, suggesting that dispersal occurs primarily among neighboring subpopulations. The 2 currently recognized subspecies of harbor seal in the Pacific, P. v. richardii of North America and P. v. stejnegeri of Asia, do not represent phylogenetically discrete mtDNA assemblages. The greatest differentiation detected was along the Commander–Aleutian Island chain, the region of the presumed subspecies boundary and a likely contact zone for expanding refugial populations of a number of marine mammal species after retreat of ice sheets. Differentiation between the Kodiak Archipelago and Prince William Sound, and between Bristol Bay and the Pribilof Islands, indicates that current management stocks are inappropriate and highlights the need for a detailed analysis of population and stock structure in Alaska. A decline in population size in Prince William Sound over the past few decades was accompanied by a discernible reduction in mtDNA diversity, manifested as a loss of rare haplotypes through random drift. A continued population decline will erode genetic diversity further, with potentially adverse effects on evolutionary potential and individual fitness.

The pampas deer, Ozotoceros bezoarticus, was, until the recent past, widespread in South America from 5°S to 41°S; however, it is now considered to be one of the most endangered South American cervids because of habitat destruction and fragmentation. A comparative craniometrical study using univariate and multivariate analyses was performed to determine whether populations of pampas deer show patterns of sexual dimorphism and geographic variation. We found that pampas deer exhibit strong sexual dimorphism. Although the species showed high levels of intrapopulation morphological variability, most of it can be attributed to males, which are highly variable within populations. The 4 populations analyzed in this work, which correspond to 4 geographic regions in South America, are significantly differentiated, with females contributing most to differentiation among populations. Furthermore, results of our morphometric analysis were in concordance with genetic levels of differentiation previously found among populations. This study also supports the recognition of 2 separate subspecies in the Uruguayan northwestern grassland (Salto Department) and the Uruguayan east grassland (Rocha Department).

Wolverines are highly vagile carnivores, with long-distance dispersal documented for males and females. Consequently, the species was thought to represent 1 large, panmictic unit in North America. In this study, we examined the connectivity of populations on the edge of their historical distribution to the larger, continuous, northern distribution of wolverines. Twenty-two regions were sampled, and 671 individuals were genotyped at 12 microsatellite loci. Our results confirmed that high levels of gene flow do occur among all the northern wolverine populations sampled. We also observed progressively increasing genetic structure at the periphery of their southern and eastern distributions, suggesting that these populations may have been partially fragmented from what was once a panmictic unit. Peripheral populations may be more susceptible to extirpation and, therefore, may be the most appropriate targets for concerted conservation efforts to prevent the elimination of wolverines from yet more of their historical range.