Bat researchers currently use a variety of techniques that transform echolocation calls into audible frequencies and allow the spectral content of a signal to be viewed and analyzed. All techniques have limitations and an understanding of how each works and the effect on the signal being analyzed are vital for correct interpretation. The 3 most commonly used techniques for transforming frequencies of a call are heterodyne, frequency division, and time expansion. Three techniques for viewing spectral content of a signal are zero-crossing, Fourier analysis, and instantaneous frequency analysis. It is important for bat researchers to be familiar with the advantages and disadvantages of each technique.

We surveyed abandoned mines, caves, and bridges to identify habitat preferences of day-roosting Townsend's big-eared bat (Corynorhinus townsendii) in northern Utah. Of 820 sites surveyed (676 mines, 39 caves, and 105 bridges), 196 (23.9%) were occupied by C. townsendii. Caves were the most frequently used type of roost (84.6%), 21.2% of abandoned mines were used as day roosts, and no bridges were used. Bats occupied mines and caves at lower available elevations (1,350–2,440 m), which were associated with sagebrush–grass steppe, juniper woodlands, and mountain brush vegetation. In general, roosts with single low (<1.5 m height) entrances were more likely to be occupied than those with multiple or tall entrances. Day roosts typically were subject to little disturbance by humans. Aspect and width of entrance, stability and complexity of interior, presence of multiple entrances, length of tunnel, amount of internal air flow, presence of multiple levels, and presence of internal water were not associated significantly with occupancy; however, maternity colonies tended to be located in large complex sites with multiple openings.

I evaluated the diet of the golden-tipped bat, Kerivoula papuensis (Vespertilionidae), at 3 sites in eastern Australia. Spiders (Araneida) dominated (>95%) feces collected from captured individuals or from beneath roosts at all sites. Araneida also occurred in 63% of 27 captured individuals; fragments of prey were located between teeth or adhering to facial fur at 1 site. A small percentage of fragments were identified to family, and all belonged to the web builders, Araneidae or Tetragnathidae. Marked K. papuensis individuals were observed only in cluttered rain forest, with all individuals flying among vegetation at an average height of about 3.4 m (range, 1–10 m). No direct gleaning attempts were observed, although hovering may have represented a strategy to capture Araneida suspended in webs. These results indicate that K. papuensis is a spider specialist, although smaller quantities of other types of prey were taken, including Coleoptera and Lepidoptera, demonstrating dietary flexibility.

Until now, our knowledge of Balantiopteryx infusca has been limited to 5 specimens collected 100 years ago. In 1991, we netted this bat at the entrances of 2 railroad tunnels near the type locality in northwestern Ecuador. The sex ratio in our small samples favored females; we found no evidence of sexual dimorphism. We refine the designation of the type locality and comment on the original series of this bat collected by W. F. H. Rosenberg.

Rates of field metabolism and water influx of 6 endangered species of marsupials living on Barrow Island, Western Australia, were measured using doubly labeled water. Field metabolic rates (FMRs) of these arid-habitat species are related to body mass according to the following equation: FMR (kJ/day) = 9.58 g^0.539 (r² = 0.935). The allometric equation for water influx rates (WIRs) in 9 arid-habitat species or subspecies obtained in our study and from the literature is as follows: WIR (ml H₂O/day) = 0.777 g^0.693 (r² = 0.848). These relationships indicate that marsupials from arid-habitats use about 35% less energy and water each day than do marsupials from nonarid habitats. Food intake for arid-zone marsupials may be estimated from the following equation: dry matter intake (g/day) = 0.501 g^0.601 (r² = 0.977). A water-economy index indicates that 3 of 6 species studied probably drank standing water, but 2 species may not have drunk water to maintain body mass during the rainless study period. The remarkably similar reduction in daily energy and water needs of arid versus nonarid Australian marsupials, compared with arid versus nonarid North American and African eutherians, suggests that this similarity is an example of convergent evolution.

We examined the effect of food quality on ingestion, digestion, and metabolic rate during pregnancy and lactation in Octodon degus, a precocial rodent, under laboratory conditions. We also examined standard energetics during reproduction in relation to litter size and litter mass. Resting metabolic rate increased significantly during lactation, and that increase resulted from variations in food quality. The highest increase (39%) in resting metabolic rate was found in lactating females maintained on high-quality food when compared with nonreproductive females. Although food intake was always higher during lactation, the maximum intake was observed among lactating females that were given high-quality food. A significant positive correlation also was found between resting metabolic rate and food intake during early lactation, which revealed an increase in energy processing during that demanding period. Significant positive relationships also were found between resting metabolic and ingestion rate relative to litter mass and size. Allocation of energy in O. degus during lactation did not follow the mode typical of precocial rodents. In contrast, conversion efficiency of metabolizable energy into tissue growth appears to be linked to environmental quality of food.

Duration of torpor by eastern chipmunks, Tamias striatus, kept at 5°C progressively increased at the beginning of hibernation (autumn phase), remained long and relatively constant (winter phase), and then decreased (spring phase) in a fashion similar to that observed in hibernators that store energy as body fat. Duration of bouts of torpor in winter and spring and amount of time animals hibernated before starting the energetically demanding spring phase were related inversely to amount of food provided at the beginning of the experiment. In addition, chipmunks given the least amount of food (400 g) continued to hibernate until they consumed all seeds; those provided with abundant food (5,000 g) terminated hibernation spontaneously early in the spring phase and remained euthermic thereafter. Animals given an intermediate ration (1,000 g) hibernated until food was gone (42%) or spontaneously terminated hibernation with abundant food uneaten (58%). Thermoregulatory responses of chipmunks appear more flexible than those of species that store energy as body fat, but the match between use and availability of energy during dormancy is imprecise.

Geographic variation in body size of Sylvilagus floridanus was investigated from 3 climatically different and disjunct regions of the range of this species (region 1, northeastern United States and southern Canada; region 2, southeastern United States; region 3, southwestern United States and northern Mexico). On a rangewide scale, body size decreased from east to west and less strongly north to south, consistent with Bergmann's rule, and was associated most strongly with variability in winter precipitation. On a regional scale, body size decreased from northwest to southeast in region 1 and southwest to northeast in region 3. We detected no trend in region 2. Large body size in region 1 was found in cold and dry environments. Body size in region 3 increased with cooler and wetter summer environments, high elevations, and low variability in winter precipitation. Bergmann's rule was supported within region 1 but not in region 2 or 3. Directions and magnitudes of trends in body size appear to depend on severity of climate; the 2 most climatically stressful regions (1 and 3) had stronger climatic correlations than region 2.

We examined the relationship between mammalian hair diameter and body mass at several taxonomic levels (interordinal, intrafamilial, intrageneric, and intraspecific) and showed a significant, positive allometric relationship between hair diameter and body size at all taxonomic levels examined. The allometric coefficient (α) ranged from 0.13 to 0.33. Within pocket gophers (Geomyidae), a significant positive relationship exists between hair diameter and rostral groove dimensions of their chewing lice, Geomydoecus, which use the rostral groove to grasp hairs of their host. Coupled with previous evidence of a strong allometric relationship between rostral groove width and louse body size, our findings suggest that hair diameter of the host is an important determinant of body size in chewing lice that parasitize pocket gophers.

Dasyuromorphian relationships were investigated using cladistic analysis for 24 species using 77 cranial and dental features. Among the 7 extinct taxa used were 6 recently described fossil species, each well represented by cranial and dental material (3 ameridelphians, 1 peramelemorphian, and 2 dasyuromorphians). Monophyly for the Dasyuromorphia and several clades widely recognized therein is supported, but in many instances, relationships among extant dasyurids departs greatly from general consensus. Where congruence with previous investigations is evident, few taxa are united by unique synapomorphies within Marsupialia. Many clades are united by combinations of locally derived features only. Bootstrap and Bremer support is weak for most clades. Thus, although supported by cladistic analysis, the status of many synapomorphies identified in the course of this study are tentative. However, for some groups, notably Dasyuridae and a dasyurid clade inclusive of all modern subfamilies, the synapomorphic nature of some derived features appears to be robust, even where they also are present in some outgroup taxa. This argument applies to shared apomorphies of the basicranium in particular. No potential sister taxon to Dasyuromorphia is favored. The case for australidelphian and microbiotheriid affinity of some American and Antarctic fossil taxa was considered to be highly equivocal.

The mitochondrial 12S ribosomal RNA (rRNA) gene was sequenced from 16 individuals representing 10 species of the genus Geomys. DNA sequences of Cratogeomys castanops, Thomomys bottae, T. umbrinus, Dipodomys phillipsii, and Pedetes capensis were included as outgroup taxa. Levels of 12S rRNA sequence divergence (average 3.5%, range 0.6–7.5%) suggested low levels of genetic differentiation within Geomys, with the transition:transversion ratio lower than that observed in other mammalian groups. Relative rate tests did not detect significant levels of rate heterogeneity between Geomys and outgroup taxa; however, certain ingroup taxa did show significant levels of rate heterogeneity when compared with other ingroup members. Phylogenies consistently supported previously identified relationships among taxa of Geomys.

Simple counts of individuals are commonly used in studies of mammalian populations. However, such counts are known to routinely underestimate population size. When used, counts are assumed to be proportional to population size. We tested the validity of that assumption by analyzing capture–recapture data on 5 species of rodents trapped at a single site during monthly sessions from 1973 through 1993. For each 3-day trapping session, we estimated numbers of animals of each species residing on our trapping grid with selected-model and interpolated-jackknife estimators from the program CAPTURE, the modified Lincoln–Petersen estimator, and the Jolly–Seber estimator. We tested for proportionality by fitting a regression line, constrained to pass through the origin, of estimated population size to each of 3 “counts”: numbers of individuals, numbers of captures, and minimum number known alive (MNKA). We then tested validity of these equations by predicting estimated population size from counts from 1994 through 1998. In general, counts were proportional to estimated numbers within a species, so counts were indices of density and yielded similar patterns of population fluctuations. However, regression coefficients, which reflected probabilities of capture, varied among species. Consequently, counts were not appropriate for interspecific comparisons of abundance, even when trapping protocols were invariant. Probabilities of capture also are likely to vary among sites, trapping protocols, and perhaps by seasons, so conditions for counts as valid indices of population size are restrictive.

Nocturnally active Acomys cahirinus and diurnally active A. russatus cooccur in hot rocky deserts, and their temporal partitioning results from competition. We studied their population biology at Ein Gedi near the Dead Sea to determine their spatial relationships and gain insight into their ecological overlap. Individuals of both species were trapped repeatedly for almost 2 years. Mean body mass did not change seasonally, and A. russatus was significantly heavier than A. cahirinus. Density of A. russatus was significantly greater than that of A. cahirinus. Acomys russatus had a shorter reproductive peak that overlapped the longer reproductive season of A. cahirinus. Acomys russatus showed a significant preference for boulder habitat versus open habitat at all seasons, whereas A. cahirinus showed a preference for boulder habitat only half of the time. Sexes of both species overlapped in home range.

The smoky shrew (Sorex fumeus) and the masked shrew (S. cinereus) are common soricids in mature southern Appalachian hardwood forests. To better understand the role of body size and niche relationships in these syntopic species, 12 50- by 50-m plots were established in the Pisgah National Forest of western North Carolina. Trapping was conducted from August through November 1996 and from March through August 1997 using Y-shaped drift fences with associated pitfalls. Prey items and microhabitat components were measured to examine correlations with abundance of shrew species. Total shrew captures (n = 176) included 105 (59.7%) Sorex fumeus and 41 (23.3%) S. cinereus. Smoky shrews were significantly larger than masked shrews in both mass and body length. Stepwise multiple regression analyses determined that a combination of litter moisture, class 5 coarse woody debris (CWD), and number of invertebrates and mountain dusky salamanders (Desmognathus ochrophaeus) was the best predictor of S. fumeus abundance (R² = 92.8%), whereas S. cinereus abundance was best explained by a combination of litter moisture, leaf-litter depth, class 3 CWD, and invertebrate size (R² = 57.7%). Microhabitat niche breadth (MB) of S. cinereus (2.11) was narrower than that of S. fumeus (2.27). Linear discriminant function analysis revealed significant ecological separation between the 2 shrew species (D² = 0.62), despite high levels of microhabitat niche overlap (MO = 65.7%). The larger body size of smoky shrews may provide an advantage in that it can use parts of the microhabitat that are inaccessible to its smaller congener, thereby reducing interspecific competition.

Herbivory and soil movement by subterranean mammals influences structure and species composition of plant communities they inhabit. Tunnels constructed by pocket gophers (Geomys bursarius) in Kansas produced an edge effect wherein biomass of the dominant plant species, big bluestem (Andropogon gerardii), increased adjacent to tunnels, then decreased, before increasing again. This wave-like phenomenon was attributed to reduction of biomass of big bluestem above tunnels releasing plants adjacent to tunnels from intraspecific competition. We tested for edge effects on vegetation over tunnels of Attwater's pocket gopher (Geomys attwateri) in a floristically diverse (>10 species of monocots, >30 species of dicots) prairie in coastal Texas. No community-level edge effect was detected; neither biomass, species richness, nor diversity of all plants, monocots alone, or dicots alone over tunnels differed significantly from that in quadrats 0 to 10, 10 to 20, 20 to 30, or 30 to 40 cm away from tunnels. Biomass of 4 individual species of plants prominent in the diet of G. attwateri did not show an edge effect. We conclude that tunnels of pocket gophers have a minor impact on plant biomass or community structure in the floristically diverse coastal prairie of Texas. This result contrasts to the negative effect of deposition of mounds above ground on plant biomass in prairies elsewhere in Texas and Kansas.

We determined characteristics of nest trees and surrounding habitats used by northern flying squirrels (Glaucomys sabrinus) in subboreal forests of northwestern British Columbia during winters 1996–1997 and 1997–1998. Nineteen radiocollared flying squirrels (12 males, 7 females) were located in 82 daytime nests. Animals used an average of 5.6 nest trees (±0.5 SE; range, 3–10) per animal. Core nest areas used by flying squirrels averaged 2.74 ± 0.62 ha in size; areas were more variable for males (range, 0.86–8.58 ha) than females (range, 0.03–2.23 ha). Nest trees were highly variable, suggesting that animals select more for suitable nest sites than for tree size: diameter at breast height was 16.7–79.0 cm, age was 42–174 years, and height was 11.2–32.7 m. A significant proportion of nest trees, however, were larger, older, and taller than trees that were randomly available in the locale of nest trees. Variation in habitats used by flying squirrels in the subboreal spruce (Picea) zone of British Columbia is evidence of the ability of this animal to occupy a wide range of conditions in a region that is not typified by old-growth forests.

We monitored movements of small mammals resident on floodplains susceptible to spring floods to assess whether and how these animals respond to habitat inundation. The 2 floodplains were associated with 6th order river segments in a semiarid landscape; each was predictably inundated each year as snowmelt progressed in headwater areas of the Rocky Mountains. Data from live trapping, radiotelemetry, and microtopographic surveys indicated that Peromyscus maniculatus, Microtus montanus, and Dipodomys ordii showed different responses to inundation, but all reflected a common tendency to remain in the original home range until “forced” to leave. The reluctance of Dipodomys ordii to abandon the home burrow often resulted in death in situ, whereas individual P. maniculatus and M. montanus moved to nearby higher ground but not necessarily toward upland. This behavior could lead to occupancy of an island that disappeared as floodwaters rose. Peromyscus maniculatus climbed into sapling cottonwood, but the quality of such arboreal refuges was unclear. We found only weak support for the hypothesis that displacement was temporary; most floodplain residents, including P. maniculatus, disappeared over the flood period. No secondary effect from flooding on adjacent upland small-mammal assemblages was detected. Our data suggest populations of facultatively riparian, nonarboreal small mammals such as M. montanus and D. ordii generally experience habitat inundation as a catastrophy. Terrestrial species capable of using an arboreal refuge, such as P. maniculatus, face a more variable risk, determined in part by timing and duration of the flood event. River regulation can affect both sets of risks.

Homestead Cave, a paleontological site located in a low-elevation arid setting in the northern Bonneville Basin of northcentral Utah, documents the local extinction of Neotoma cinerea during the Middle Holocene. N. cinerea is present there today, and the Homestead Cave record suggests that recolonization likely occurred sometime prior to 1,000 years ago. This history supports the view (forwarded by T. E. Lawlor) that cross-valley dispersal by mammals that generally are most abundant in cooler and moister (and therefore higher elevation) parts of the Great Basin is still occurring, showing that Brown's model of Great Basin montane mammalian biogeography is incorrect. These dispersal patterns suggest that conservation efforts directed toward montane mammals in the Great Basin must include low-elevation access corridors to mountain masses.

In 5 autumns and 1 summer during a 13-year study of Richardson's ground squirrels (Spermophilus richardsonii) in southern Alberta, Canada, carcasses of 27 ground squirrels were scatter hoarded by badgers (Taxidea taxus). Cached ground squirrels, which rarely exhibited external signs of trauma, were hoarded singly either above ground (n = 16) or underground (n = 11) in a curled head-to-tail posture in a pocket of firm soil and then covered with loose soil. Except for 3 carcasses cached by a mother badger in June, remaining ground squirrels were cached between 7 September and 28 November, with most hoarding (n = 17) occurring from 16 October to 17 November. Of 24 ground squirrels cached in autumn, 23 were in hibernation at the time of capture. Badgers retrieved the majority (14 of 18 available) of carcasses, with the latest retrieval occurring on 9 December. Carcasses were retrieved, in the order they were cached, 1 to 55 days (X̄ = 14 days) after caching. Cache storage, cache retrieval, and consumption of freshly caught prey were prevalent in autumn, often occurring on the same night, indicating that caching contributed to fattening in autumn rather than as a food reserve to be used by badgers during winter.

We examined shelter and maternity dens used by 97 adult female polar bears (Ursus maritimus) in relation to conditions of sea ice. Obligate use of maternity dens for pregnancy, birth, and lactation varied little with latitude or area. In contrast, timing of facultative use of shelter dens switched from autumn in the southern area (<70°N) to winter in the northern area (>75°N). For the southern area, 13 of 16 female polar bears used shelter dens in autumn versus winter (median dates of entry and exit, 11 September and 2 November; total = 56 days), whereas in the northern area, 11 of 17 bears used shelter dens in winter versus autumn (median dates, 24 December and 2 March; total = 65 days). Difference in facultative use of shelter dens was associated with conditions of sea ice. Southern regions had no sea ice when polar bears used shelter dens. In contrast, northern areas had more constant ice conditions that included presence of ice throughout the year. Southern regions seem to have greater primary productivity and more seals as a result of a pronounced seasonal cycle of annual ice. Polar bears in northern areas responded to the more constant ice conditions and less productive environment with use of shelter dens during the period with lowest seal accessibility.

We studied interactions of reintroduced wolves (Canis lupus) with bison (Bison bison) in Yellowstone National Park. Only 2 of 41 wolves in this study had been exposed to bison before their translocation. Wolves were more successful killing elk (Cervus elaphus) than bison, and elk were more abundant than bison, so elk were the primary prey of wolves. Except for a lone emaciated bison calf killed by 8 1-year-old wolves 21 days after their release, the 1st documented kill occurred 25 months after wolves were released. Fourteen bison kills were documented from April 1995 through March 1999. All kills were made in late winter when bison were vulnerable because of poor condition or of bison that were injured or young. Wolves learned to kill bison and killed more bison where elk were absent or scarce. We predict that wolves that have learned to kill bison will kill them more regularly, at least in spring. The results of this study indicate how adaptable wolves are at killing prey species new to them.

Home range, movements, and activity patterns of pampas deer (Ozotoceros bezoarticus) were studied in Emas National Park, State of Goiás, Brazil. Four pampas deer were located daily during 1 year by radio tracking. Additionally, during 8 sampling periods, locations were determined every 30 min for 12 consecutive hours to determine activity patterns. Vegetation was sampled monthly to detect for seasonal variation in food availability. Pampas deer were active during the day and night, and individual variation in activity patterns was observed. Average home ranges of pampas deer were larger than the average area used by other Odocoileinae. Home ranges were similar in size in the dry (April–September) and wet (October–March) seasons, but deer moved more during the rainy season—a pattern apparently related to availability of flowers.

We studied effects of maternal age, body mass, and parturition date on birth mass and stage of development at birth in harbor seals (Phoca vitulina) on Sable Island, Nova Scotia, over a 10-year period. As predicted, effects of maternal mass and age on pup traits varied with maternal age. Premature pups, characterized by extensive fetal pelage termed lanugo, weighed 20% less than newborns without lanugo and were born early in the season to low-body-mass females 4–6 years of age. Among intermediate-age females (7–10 years old), percentage of lanugo on pups was correlated negatively with female postpartum body mass but not with female age. Thus, maternal condition rather than age had stronger effects on stage of development of offspring at birth. Overall, maternal age explained 54% of the variance in birth mass, whereas postpartum mass of females explained only 20% of the variance. These relationships did not differ with sex of the pup, although male pups were 3.7% heavier than female pups. Effects of maternal age were strongest among young females; however, reproductive parity was more important than age itself in determining offspring birth mass.

Clear genetic and osteological characters exist to distinguish 2 sympatric species of bottlenose dolphins (genus Tursiops) in the waters of China. However, these characters are not useful for the identification of free-ranging dolphins. To determine if these species could be differentiated by external morphology, a discriminant analysis was performed on 8 external morphometric characters of 57 specimens, 40 of which were classified a priori as T. truncatus and 17 as T. aduncus using genetic, osteological, and other information. External morphological separation of the 2 species was highly significant. Furthermore, discriminant scores were nonoverlapping, and classification functions were successful in classifying several new specimens from the waters of China and Indonesia. Rostrum length as an absolute measure and as a proportion of total body length or snout-to-eye length revealed nonoverlapping distributions for the 2 species in the waters of China and thus offered useful field characters for classifying fresh carcasses, stranded individuals, captive specimens, photographs, and in some cases free-ranging individuals.