Phylogenetic relationships among 8 subspecies of Neotoma albigula and sister species from the United States and Mexico were examined using DNA sequence data from the mitochondrial DNA cytochrome-b gene. Parsimony, likelihood, and neighbor-joining analyses revealed a strong dichotomy between populations of N. albigula from Texas and eastern Mexico (eastern form) and those from New Mexico, Arizona, and northwestern Mexico (western form). These analyses indicate presence of 2 cryptic species within this taxon that are paraphyletic under current taxonomy. A sister-group relationship was found between N. albigula from Texas and eastern Mexico and N. micropus, whereas populations of N. albigula from New Mexico, Arizona, and northwestern Mexico formed a sister-group relationship with N. floridana. That latter group in turn formed a sister-taxon relationship to the Texas–eastern Mexico N. albigula and N. micropus clade. The Rio Grande and Rio Conchos seem to have been the major barriers restricting gene flow between ancestral populations of a N. floridana–like woodrat. Populations of N. floridana were further isolated geographically by reduction of suitable habitat brought about by changing climatic patterns that allowed formation of xeric plant communities soon after the end of the Late Wisconsin.

DNA sequence data from 2 nuclear introns (mitochondrial malate dehydrogenase intron 7 and acid phosphatase type V intron 2) were collected for 9 taxonomic units of rodents, 8 of which were in the genus Mus. Data were used to infer phylogenetic history of the 9 taxa, which was then compared with a consensus phylogeny taken from previous literature. In general, the nuclear intron data provided strong support (bootstrap proportions > 80) for relationships accepted in the consensus tree. The intron data disagreed with previous mitochondrial data in that 2 M. m. domesticus sequences were paraphyletic with respect to M. m. castaneus and M. m. musculus. This paraphyly, if real, likely reflects the longer lineage-sorting time of the nuclear genome compared with the mitochondrial genome. Introns seem to provide an attractive source of nuclear DNA sequence data for phylogenetic analysis, but mitochondrial data are likely to be superior for very recent divergences.

We evaluated genetic variation in Gapper's red-backed vole (Clethrionomys gapperi) at 2 microsatellite DNA loci and related our results to the biogeographic history of the southern Appalachians. To investigate population genetic structuring within relictual habitats, 222 individuals were sampled from 9 sites, including 2 populations suspected to have been isolated since the Wisconsin glacial retreat. Genetic structuring was evident among the majority of the sampled populations. Unbiased estimates of exact P-values revealed significant allelic differentiation between 15 of 36 population pairs. Overall estimates of F_ST and ρ were 0.07 and 0.10, respectively, indicating moderate genetic subdivision. Overall gene flow was estimated indirectly with 3 methods and was 1.13–4.44 migrants/generation. The hypothesized isolation of 2 islandlike populations at Massanutten and Peaks of Otter was supported by our data and was most apparent in the Massanutten population, where genetic diversity was low compared with all other populations. The unique genetic structure of the population at Massanutten also may be related to habitat disturbances. Genetic patterns observed in relict populations of the red-backed vole may provide insight into genetic structuring of codistributed boreal populations in the southern Appalachians.

Nucleotide sequence data from the mitochondrial DNA (mtDNA) cytochrome-b gene and allozymic data were used to infer the evolutionary and biogeographic histories of New World tree squirrels of the genus Tamiasciurus. Phylogenetic analyses of the cytochrome-b data support the existence of 3 mtDNA lineages within Tamiasciurus: a western lineage consisting of populations of T. douglasii from western British Columbia (Canada), Washington, Oregon, and California, and T. mearnsi from northern Baja California (Mexico); a southwestern lineage consisting of populations of T. hudsonicus from New Mexico and Arizona; and a geographically widespread lineage comprising populations of T. hudsonicus from the remainder of the species' range. Levels of mtDNA sequence variation observed within and among populations of Tamiasciurus were small (0–2.4%), suggesting that contemporary geographic patterns of genetic variation in Tamiasciurus have been established relatively recently (i.e., in the Late Pleistocene). Allozyme analyses also support a close relationship among extant populations of Tamiasciurus. No fixed allelic differences were observed among the 3 recognized species and interspecific genetic distances (Nei's D) were substantially less than those typically observed between sibling species. Although differing from the current taxonomy in several respects, geographic patterns of genetic variation observed within Tamiasciurus are similar to those observed in a variety of North American boreal forest taxa and most likely reflect effects of forest fragmentation associated with glacial cycles of the Pleistocene.

Although the order Chiroptera has received extensive systematic attention during the past century, because of incongruence among studies and a paucity of synapomorphic characters, many problems associated with higher-level phylogeny and taxonomy of bats still exist. One notable example regards phylogenetic affinities of Old World Myzopodidae and Neotropical Furipteridae, Natalidae, and Thyropteridae. Traditionally, these 4 families are believed to have shared a most recent common ancestor, yet, until recently, no study has specifically tested this hypothesis. A recent phylogenetic analysis detected strong bootstrap support for monophyly of these 4 families and recommended recognition of the superfamily Nataloidea to document this relationship. We used variation in mitochondrial DNA to evaluate the monophyly of Nataloidea. Phylogenetic analysis of DNA sequences from 3 adjacent genes (12S rRNA, tRNA^Val, and 16S rRNA) failed to support monophyly of Nataloidea. Furipteridae, Natalidae, and Thyropteridae were related most closely to Noctilionoidea, whereas Myzopodidae represented a basal microchiropteran lineage. Our phylogeny is concordant with current geographic distributions and limited fossil record for the 4 families.

We used phylogenetic analyses of mitochondrial genes, cytochrome-b, and reduced nicotinamide adenine dinucleotide dehydrogenase 2 (ND2) to test the recent proposal that 3 species of large-footed Myotis (adversus, macropus, and moluccarum) occur in Australia. Analyses show that all Australian populations of large-footed Myotis form a monophyletic group to the exclusion of a group containing Indonesian populations of M. adversus. The haplotype divergence between these 2 groups is high (11.8–12.2%) and is comparable with typical species-level divergences in Chiroptera. Within Australia, 2 recently diverged monophyletic groups of haplotypes are found that are not concordant in geographic distribution with species boundaries based on morphology. Analysis of these data suggests that only a single species of large-footed Myotis occurs in Australia, and because this species is taxonomically distinct from M. adversus in Indonesia, it should be known as M. macropus. Our data also show that 2 species of Myotis occur in Papua New Guinea.

We explored the ability to discriminate between echolocation calls of 20 adult and 20 juvenile big brown bats (Eptesicus fuscus). Variables describing each call were entered into discriminant function analyses (DFAs) to assess the success of call separation by age, sex, and individual. In agreement with earlier findings of age-dependent differences in the echolocation calls of big brown bats, we could discriminate calls by age class (juvenile versus adult) with 75% correct classification by DFA. We were not able to separate calls by sex. For discrimination of individuals, we found 63% correct classification (compared with 2.5% expected by chance alone). Correct classification was significantly higher for adults than for juveniles (74% versus 69%), perhaps indicating that calls become more stable as a bat ages.

The relative importance of plants and insects as sources of protein through the year was evaluated in 2 bat species in a seasonal forest in the neotropics using stable-isotope analysis of carbon and nitrogen. Artibeus jamaicensis, a frugivore, met almost all of its protein requirements from plants with no seasonal or sexual variation. In contrast, Glossophaga soricina, a nectarivore, relied mostly on insects, but in females, plants and insects were equally important in the early rainy season and in the mid dry season. Evidence of changes in food origin of protein associated with reproductive activity was not detected in either species.

At 2 locations in California (coastal, Tocaloma; desert, Caliente), analysis of feces presented a significantly higher number of prey types for the diets of Antrozous pallidus than analysis of culled parts of prey. Analysis of diet by culled parts was biased toward larger, harder prey, and some softer, smaller prey were missed altogether. Observation of individuals feeding revealed that some bats ate prey without culling any parts, whereas others culled only the hardest and largest parts. Analysis of feces from tagged adult male pallid bats from Tocaloma (1993–1994) and Caliente (1994–1995) suggested that bats were generalists, but whereas diets of individuals at Caliente reflected the average diet for the group, none of the individuals at Tocaloma ate the average diet. Variation in the diets of A. pallidus reflects prey availability and individual foraging behavior. Tocaloma bats did not significantly change their diets throughout summer; Caliente bats did. Bats from Caliente and Tocaloma ate different prey than arthropods caught in pit traps, suggesting that bats in both populations were selective foragers. In captivity, hunting A. pallidus took flying and nonflying prey. Some flying prey were forced against a surface before capture, adding a novel dimension to the range of behavior involved in “gleaning.”

Authors and dates of publication of family-group names based on extant bovids are reviewed. Tragelaphini is found to be attributable to Blyth, 1863, not Jerdon, 1874; Cephalophinae to Blyth, 1863, not Gray, 1871; Reduncinae to Knottnerus-Meyer, 1907, not Lydekker and Blaine, 1914; Alcelaphinae to Brooke in Wallace, 1876, not de Rochebrune, 1883; Hippotraginae to Sundevall in Retzius and Lovén, 1845, not Retzius and Lovén, 1845, or Brooke in Wallace, 1876; Naemorhedini to Brooke in Wallace, 1876, not Pilgrim, 1939; and Ovibovini to Gray, 1872, not Gill, 1872. The authors, dates, and original spelling for other names also must be corrected. Hippotraginae must be validated by dating the genus Hippotragus from Sundevall in Retzius and Lovén, 1845, with type by monotypy H. equinus, not from Sundevall, 1846. Adenotinae (and Eleotraginae), Connochaetini, Nesotragini, Strepsicerotini, Sylvicaprinae, and Tetracerini are senior synonyms of Reduncinae, Alcelaphini, Neotragini, Tragelaphini, and Boselaphini, respectively. Neotragini and Reduncinae are nomena protecta and are to be used in preference to their less familiar senior synonyms. Until their validity is confirmed, Boselaphini, Tragelaphini, Cephalophinae, and Alcelaphinae also are to be employed in preference to their senior synonyms. If required, Connochaetini can be treated as a tribe of Alcelaphinae despite its seniority.

Fluctuating asymmetry (FA) refers to small random deviations from perfect bilateral symmetry. Because FA reflects the ability of individuals to undergo stable development, it may provide a potential measure of individual quality. We assessed whether horn asymmetry was related to life-history traits in individually marked mountain goats (Oreamnos americanus) over 10 years. Horn length exhibited FA and was related positively to absolute asymmetry in both sexes. Relative asymmetry in horn length did not vary with either sex or age. Horns of surviving juvenile (1- and 2-year-old) males were more symmetrical than horns of those that died, but horn asymmetry did not affect survival of juvenile females or adults of either sex. Horn asymmetry was not related to body condition in juveniles of either sex or in adult males, but adult females with symmetrical horns were in better condition than those with asymmetrical horns. Similarly, horn asymmetry was related negatively to body mass in adult females but not in other sex–age classes. Horns of dominant females were more symmetrical than those of subordinate females. Females that produced a young in their year of capture had more symmetrical horns than females that did not reproduce, and horn asymmetry was correlated negatively with long-term reproductive success in females. Nonetheless, asymmetry in horn length of females did not influence survival of young and was not related to age of primiparity. Analysis of our results indicates that asymmetry in horn length is a phenotypic marker of individual quality in females but does not point to a strong relationship between horn asymmetry and life-history traits in adult males.

I examined prevalence of mandibular oligodonty in wild sheep (Ovis) and related it to evolutionary theory and classification. Inspection of 5,300 mandibles that included most subspecies of sheep revealed that this anomaly was widespread in New World sheep (subgenus Pachyceros) but was rare in Old World sheep (subgenus Ovis). Among the pachyceriform sheep, Siberian snow sheep (O. nivicola) had the highest prevalence of mandibular oligodonty (60.3%), followed by Dall's sheep (O. dalli, 23.0%), and bighorn sheep (O. canadensis, 10.1%). In Old World sheep, occurrence averaged 1.7% for argalis (O. ammon), 1.0% for urials (O. vignei), and 1.7% for mouflons (O. gmelini). Prevalence in domestic sheep was 4.3%. Overall, more recently evolved types exhibited the anomaly to a greater degree than did more primitive ones.

We examined diets of bison (Bos bison) bulls, cows, juveniles, and calves to determine differences in quality of diets between groups. Our results showed that bulls had a significantly higher proportion of C₄ grasses in their diet than cows, juveniles, or calves. Diets of calves were of higher quality than diets of bulls, cows, or juveniles. Our results provide support for the sexual dimorphism–body size hypothesis of sexual segregation in large ungulates.

Large males are solitary or occur in small groups in numerous ruminants. I propose that large males may become less social because of differences in costs and benefits of aggression as they age and increase in size and social status. Outside the mating season, large males have little to gain from sparring and interacting aggressively with other large males. I examined if large male Roosevelt elk (Cervus elaphus roosevelti) were more solitary or in smaller groups than other size or sex classes, associated with other large males, directed more aggression to small males, and displayed behaviors that reduced aggression when in groups. Large males were in the smallest groups and solitary more than twice as often as small males and females, and groups with large males had ≥50% of the group composed of large males. In relation to small males, large males sparred less frequently, were more dispersed in groups, and directed more aggressive behaviors toward them. Differences in costs and benefits of aggression between small and large males may help explain the asocial nature of large males.

We studied behavioral and ecologic effects of differential predation pressure on moose (Alces alces gigas) in the eastern Talkeetna Mountains, Alaska, during 1996–1998. Annual mortality from grizzly bear (Ursus arctos) and wolf (Canis lupus) predation was higher for solitary yearling moose than for dependent yearlings (those with adults) and solitary adults. We tested hypotheses that solitary yearlings have heightened levels of vigilance and greater variation in vigilance responses and spend more time near protective cover than do dependent yearlings or adults. Proportion of time spent vigilant did not differ between solitary and dependent yearlings, and no differences were found between solitary yearlings and adults. However, variation in vigilance increased with distance to protective cover for yearlings but not for adults. Only at distances ≥20 m from protective cover did variation in vigilance differ between solitary yearlings and adults. Increased variation in vigilance at distances far from protective cover, locations where putative vulnerability to predators is greatest, may account for increased mortality among solitary yearlings. Mean distance to protective cover was not different between solitary and dependent yearlings or between solitary yearlings and adults. Because hypotheses regarding differences in vigilance and use of protective cover between age and social status categories generally were not supported, other factors may be involved in promoting high vulnerability of independent yearlings to predation. Smaller body size and maternal defense are unexplored alternatives for explaining differential mortality between yearlings with and without mothers.

We applied optimal foraging theory to test effects of habitat and predation risk on foraging behavior of mule deer (Odocoileus hemionus) subject to predation by mountain lions (Puma concolor). We predicted that deer would spend less time foraging, have higher giving-up densities of food (GUDs), and have higher vigilance behavior when occupying patch edges than when in open and forest interiors. We also measured GUDs in 3 microhabitats within 3 forest types. We used pellet-group surveys to estimate habitat and microhabitat use, and we assessed vigilance behavior with automatic camera systems. The GUDs (perceived predation risk) were greater in forests of Douglas fir (Pseudostuga menziensii) than mountain mahogany (Cercocarpus ledifolius). In forests of Douglas fir, GUDs were greatest in the forest interior, declined at the forest edge, and were lowest in the open microhabitat. Microhabitat features did not influence GUDs in the mountain mahogany forest. Pellet-group data indicated more activity in the open than in the edge or forest. Based on photographs, deer were more vigilant at forest edges than in open and forest areas. We concluded that deer are responding to predation risk by biasing their feeding efforts at the scale of habitats and microhabitats and altering their habitat-specific patterns of vigilance behavior.

Photographic identification of naturally marked animals is a powerful and nonintrusive technique for obtaining information on behavior, population size, and life-history parameters in wild populations. Yet handling large quantities of photographs is time consuming and prone to error. Computer-aided matching can limit the number of photographs that must be examined visually to confirm that 2 sightings are the same individual. To identify individuals, I used a 3-dimensional (3-D) computer-matching system to aid in matching nearly 10,000 photographs of Serengeti cheetahs, Acinonyx jubatus, taken over 25 years. Accuracy in matching 2 photographs increased to 100% as the computer-generated similarity coefficient increased to 0.600 on a scale from 0 to 1. Probability of missing a match decreased to 6.4% when I used a threshold of similarity of 0.450. Poor quality of photographs decreased accuracy and resulted in up to 33% of matches being missed. Comparisons of photographs at skewed camera angles generally reduced similarity coefficients. Similarity coefficients were no higher for related or unrelated animals, suggesting that the technique is not appropriate for distinguishing subtle similarities. Because 3-D computer-aided matching does not require familiarity with distinctive features of the particular study animal, it is robust to matcher inexperience. This technique can be modified for other species that have complex and variable pelage patterns.

Enamel of several fossil and recent arctoid carnivores was studied with light and scanning electron microscopy. As in other carnivorans, 3 types of Hunter–Schreger bands (HSB) were observed: undulating, acute-angled, and zigzag HSB, which differ in their 3-dimensional complexity. Data on arctoid carnivores were used to test the hypothesis that zigzag HSB evolved multiple times to resist cracking of the enamel under high tensile stress. Distribution of HSB, except presence of zigzag HSB in the herbivorous panda, Ailuropoda, supported the hypothesis.

We studied the influence of prey size and abundance on social organization and space use by eastern coyotes (Canis latrans) in 2 areas of Nova Scotia, Canada. Breeding pairs formed the nucleus of coyote social groups, and these often traveled with 1–3 other coyotes during winter. Increased use of white-tailed deer (Odocoileus virginianus) was insufficient to explain group size and cohesiveness by eastern coyotes. Winter-traveling group size was similar for family groups using deer (X̄ = 2.6) or snowshoe hares (X̄ = 2.7) as a primary prey in winter. Estimated densities of coyotes in winter was 4.3–13.9 coyotes/100 km². Coyotes used the same general areas during winter and summer and from year to year. However, territory sizes decreased with increasing densities of deer (partial r² = 0.21, P = 0.043) and hares (partial r² = 0.40, P = 0.007). During winter, coyotes used areas of high deer density in proportion to their availability, but in some instances, they used areas that contained few or no deer proportionately more than expected, probably because deep snow and few trails increased vulnerability of deer in these areas. Territoriality seemed to prevent coyotes from concentrating in deer wintering areas and kept the coyote : deer ratio relatively low (<1:25).

American martens (Martes americana) are associated strongly with mature conifer forests and once occurred throughout the mountains of the coastal Pacific states. We sought to document the distribution of martens in this region using historical records and to understand recent change in their distribution. We described the distribution of martens from 1900 to 1949 using museum and trapping records and compared it to recent (1989–1998) detections at camera and track-plate stations. Martens were detected at only 12 of the 237 (5.1%) survey sample units in coastal California, Oregon, and Washington. Martens are absent from most of the historical range of the Humboldt marten (M. a. humboldtensis) in California and also may have declined on the Olympic Peninsula of Washington. Few data exist from northwestern Oregon and southwestern Washington, but the limited amount of protected public land and absence of reported road kills are reasons for concern for populations in this region. Martens still occur in the central and southern coastal mountains of Oregon. Our results suggest that conservation of martens in coastal forests will require new initiatives to protect existing populations and new efforts to document all populations of martens in this region. Conservation measures should include a reevaluation of timber harvest plans that affect habitat in coastal forests, interagency cooperation on a coastal marten conservation assessment, and the collection of new survey information, especially on private lands in southwestern Washington and northwestern Oregon.

We used microsatellite genotyping to determine the genetic relatedness of 7 apparent twin dyads of Weddell seals (Leptonychotes weddellii) born in McMurdo Sound, Antarctica. Genetic evidence for twinning in wild pinnipeds has not been reported previously. A review of 14 years of demographic data combined with pathological exams, behavioral observations, and molecular genetic evidence suggests that twinning is extremely rare in Weddell seals and that females do not wean both pups in the wild. The incidence of live twin births was about 0.1% (2/1,439 births), recorded over 3 seasons in Erebus Bay, McMurdo Sound. Additionally, a single case of true twinning was documented from 23 known pregnancies observed in an isolated population of Weddell seals located within McMurdo Sound. The 3 twin sets were dizygotic full siblings, 1 nontwin dyad represented a case of adoption, and the 3 remaining putative twin sets were identified as instances of foster nursing. These results indicated that observation of mother–offspring behavior was not a reliable method for identifying a twin birth in this species. Use of genetic techniques to verify presence of twins in species with low or unknown twinning rates offers the opportunity for a refinement of estimates in studies of reproductive success, fostering behavior, and adoption.

Growth models (mass and length) were constructed for male (≥1 year old), female (≥1 year old), and pregnant female Steller sea lions (Eumetopias jubatus) shot on rookeries or haulouts, or in coastal waters of southeastern Alaska, the Gulf of Alaska, or the Bering Sea ice edge between 1976 and 1989. The Richards model best described growth in body length and mass. Females with fetuses were 3 cm longer and 28 kg heavier on average than females of the same age without fetuses. Males grew in length over a longer period than did females and exhibited a growth spurt in mass that coincided with sexual maturity between 5 and 7 years of age. Average predicted standard lengths of males and females ≥12 years of age were 3.04 and 2.32 m, respectively, and average predicted masses were 681 and 273 kg, respectively. Maximum recorded mass was 910 kg for an adult male. Males achieved 90% of their asymptotic length and mass by 8 and 9 years of age, respectively, compared with 4 and 13 years, respectively, for females. Residuals of the size-at-age models indicated seasonal changes in growth rates. Young animals (<6 years old) and adult males grew little during the breeding season (May–July), and adult males did not resume growth until sometime after November.

We analyzed growth of the sigmodontine rodent Oryzomys albigularis under laboratory conditions, fitting data to growth models, to test the null hypothesis that no differences exist between sexes. We propose a biologic criterion for growth-model selection, under the assumption that the curve should show critical stages of the organism's postnatal development and growth. Following this approach, growth of O. albigularis best fits a logistic curve. Our results show that, although males and females grow at the same rate, the final size is significantly different, being slightly dimorphic. These results, together with behavioral observations of the animals in the laboratory, support the hypothesis of a monogamic mating system for this species.

We evaluated the accuracy in using the Small Animal Composition Analyzer (EM-SCAN®, Model SA-2) for estimating body composition of live meadow voles (Microtus pennsylvanicus). To investigate the necessity for a species-specific calibration equation, we compared the average error in estimates of lipid mass using meadow vole data in calibration equations derived for meadow voles in this study to equations derived for prairie voles (very similar in size and shape to meadow voles) and to those provided by the manufacturer. Analyses using a complete data set (n = 27 voles) and 2 subsets representing “lean” voles (n = 16) and “fat” voles (n = 11) were performed. The equation derived for meadow voles more accurately estimated lipid mass than the other equations with an average error of 1.55 g compared to 3.64 g using the prairie-vole equation and 4.73 g with the manufacturer equation, supporting the need for a species-specific equation even with species of very similar size and morphology.

The effect of light intensity on activity was investigated in a study of captive leaf-eared mice, Phyllotis xanthopygus. This nocturnal mouse lives in rocky outcrops but forages in open areas with little vegetative cover. Primary predators are raptors and canids, all of which are expected to have increased hunting success under higher levels of moonlight. Because of this correlation between light intensity and predation risk, we predicted that increased light intensity during the dark period would result in decreased nocturnal activity. Data were collected continuously for 3 days under varying light intensities and were analyzed using cosinor analysis to estimate parameters describing the activity rhythm (mesor, amplitude, and acrophase). Number of diurnal activity bouts increased after exposure to light intensities similar to full moonlight (3.0 lux). Total activity of mice in middle (1.5 lux) and high (3.0 lux) light treatments was depressed as evinced by significantly lower mesor and amplitude estimates compared with those of mice in control conditions (0.0 lux). The acrophase also was significantly different between the control and the 2 treatment groups.

The “triangular” pattern of reproduction in arvicoline rodents predicts small fecundity early and late in life and high fecundity in the middle. In producing this pattern, the effects of maternal age and parity are typically highly confounded. We present results of a laboratory study designed to disentangle these effects in the common vole (Microtus arvalis) by analyzing variation in sizes of the first 2 litters born to 3 age classes of females subjected to photoperiods of 8 h and 16 h of light. Although the youngest females, paired at 2 weeks of age, decreased size of the 2nd litter in either light environment, the older 2 classes, paired at 3–4 months and 1 year of age, increased their 2nd litters, as predicted by the triangular pattern. This age-specific effect of parity could be explained by differences in the size of 1st litters.

Although facultative torpor has been observed in laboratory populations of black-tailed prairie dogs (Cynomys ludovicianus), it is widely believed that these animals remain normothermic throughout winter in the field. We monitored body temperatures (T_b) of 5 black-tailed prairie dogs in the field for about 100 days during winter and spring 1998–1999. All animals entered torpor during this period. Major torpor bouts averaged 140.5 h ± 2.4 SD (range = 77.6–214.4) with a minimum T_b of 19.0 ± 3.6°C. Minor torpor bouts averaged 46.2 ± 20.9 h (9.5–98.5), with minimum T_b reaching 30.3 ± 2.3°C. There was no distinct relationship between ambient air temperature (T_a) and entry into torpor. All torpor bouts occurred following a sudden reduction in T_a, but not all sudden reductions in T_a induced torpor. Precipitation was not associated with entry into or arousal from torpor. Our study demonstrates that facultative torpor occurs in free-ranging black-tailed prairie dogs in the field.

We report a previously undescribed seed-storing behavior of banner-tailed kangaroo rats (Dipodomys spectabilis) that reduces losses to microbes. D. spectabilis cuts upper stems of the grass Sporobolus cryptandrus into 3- to 5-cm sections that we refer to as seed stems. Seeds within these seed stems remain attached to their rachis and are protected by an enveloping leaf. Most seed stems are bundled together tightly in packs of about 50 to several hundred individual stems and jammed vertically into cul-de-sacs excavated in the walls of their burrows. This behavior reduces rate of infection of seeds by fungi and also may reduce number of seeds pilfered by arthropods. Furthermore, compared with seeds of S. cryptandrus housed in middle sections of seed stems, those housed in the ends had a higher rate of infection. Simulated seed stems of wheat straw containing seeds of white millet (Panicum miliaceum) had a lower rate of infection and fewer species of fungi than seeds only protected by wire mesh. Seeds closer to the top of the simulated seed stems were more likely to be infected and had more species of fungi. Community structure and dynamics of microfungi also appeared affected by the protective layering of seed stems. We suggest that D. spectabilis manages the structure, and perhaps dynamics, of communities of microbes within their food caches by modifying position, location, or organization of food items.

We assessed the spatial and temporal pattern and scale of an irruption by a population of deer mice (Peromyscus maniculatus) in the summer of 1997 in New Brunswick, Canada. We tested the prediction that spatial scales finer than the extent of the irruption would not reveal domains of population growth. Increases in the abundance of mice were seen across an extensive set of study grids (separated by >15 linear kilometers); however, growth rates were autocorrelated spatially over short distances (<300 m). The extensive irruption may have been a result of finer-scale irruptions occurring simultaneously.

Causes of cyclic fluctuations in abundance (population cycles) of some small-mammal populations remain poorly understood despite 6 decades of research and >20 hypotheses. Population cycles are demographic processes and cannot be fully explained without considering demographic mechanisms that underlie cyclic fluctuations in abundance. From simulation studies, we have recently shown that phase-related, density-dependent changes in age at maturity, abetted secondarily by changes in juvenile survival, are likely the main demographic causes of cyclic fluctuations in population size. The suggested mechanism of population cycles is based primarily on changes in age at maturity (α); we refer to this idea as the α-hypothesis. Here, we fully develop the α-hypothesis and present a testable, demographically based, mechanistic explanation of population cycles. The α-hypothesis identifies the demographic basis of population cycles and provides a mechanistic explanation of how changes in key demographic variables (age at maturity and juvenile survival) might cause cyclic fluctuations in abundance and biologic attributes of the cycles. The α-hypothesis is supported by, and logically consistent with, empirical patterns of life history and dynamics of cyclic populations of small mammals. Future research should focus on empirically determining causes of phase-related changes in age at maturity and juvenile survival.

The American Society of Mammalogists has held 80 annual meetings between 1919 and 2000. These meetings have been held in 32 states, the District of Columbia, Canada, and Mexico. At least 86 people have served as the chair or co-chair of the Local Committee planning the meetings. The number of technical presentations has grown from a low of 17 in 1921 to 340 in 1994. Symposia were an early feature of annual meetings but did not become a regular feature until 1971. Poster presentations were introduced in 1979 and reached a high of 195 posters at the 1994 annual meeting. Two trends are evident in the analyses of presentation data from annual meetings. There has been a major increase in the number of presentations, especially since 1968, when the number of presentations first exceeded 100. The other trend is the significant increase of participation of women scientists in the annual meetings of the Society. This trend had its origins in the late 1960s and was significantly aided by the addition of poster sessions, which have been popular venues for women scientists to present their research results. However, women are not as well represented as organizers or invited participants in symposia.