Marine mammals are a K-selected relict megafauna that escaped the mass extinctions that affected their terrestrial counterparts at the end of the Pleistocene. Over the last 500 years they have been severely impacted as humans have mastered the marine environment. Some stocks and species went to extinction, and extinction of others was narrowly averted through international efforts regulating commercial exploitation. In the late 20th century new threats arose through contamination of the marine environment and these will be exacerbated and added to as human numbers double and economies grow over the next century.

Critical habitat for marine mammals is defined in terms of the functioning ecological units required for successful breeding and foraging. This definition is used to consider the potential effects of environmental change in the 21st century on abundance and distribution of marine mammals. Critical habitat for breeding can be identified relatively easily for pinnipeds and some coastal and freshwater cetaceans. Critical habitat for foraging is more difficult to define, particularly for pelagic species. However, telemetry-based studies have indicated that relatively localized areas may be particularly important for some species. Habitat degradation, as a result of reduction in prey density and increased risks of mortality due to human activity, is likely to be a problem for most species. Ice-breeding seals, particularly those that are endemic to inland seas and large lakes, are most likely to be affected by climate change. Climate change will also affect distribution and availability of prey in the short and long term. Although highly mobile species, such as marine mammals, can respond more rapidly to effects of climate change than their terrestrial counterparts, central-place foragers, such as many otariid seals, may still be seriously affected.

We discuss the potential for commercial fisheries to adversely impact ≥1 population of marine mammal by the end of the 21st century. To a large degree, patterns over the last 50 years regarding human population growth, success and failure in marine-fisheries management, and life history and status information on marine mammals are the basis for 6 predictions. First, annual worldwide landings of fish and shellfish by the end of the 21st century will be less than 80 million tons. Second, virtually all of the predictions regarding species composition and energy flow within a marine community, based on models developed to date with incomplete information on species abundance, food habits, genetic effects of fishing, and variability of predator food habits, will prove wrong on a decadal or longer time scale. Third, the most common type of competitive interaction between marine mammals and commercial fisheries will be that in which commercial fisheries adversely affect a marine-mammal population by depleting localized food resources without necessarily overfishing the target species of fish (or shellfish). Because of this, the number of extant populations and species richness of marine mammals will be reduced by the end of the 21st century, and coastal populations and species will be affected more negatively than will noncoastal species. Fifth, predator control programs designed to reduce local populations of marine mammals will be common without changes in existing forms of fishery management. Finally, protein from marine mammals will become a more important component of the human diet than it currently is.

Historically, distributions of plants and animals have shifted with changes in regional and global temperatures. Current predictions from general circulation models show changes in level and variation in temperature and rainfall over the next several decades. The magnitude and direction of such changes vary regionally. Studies are beginning to show that these changes will impact distribution of species of plants and animals, and, concomitantly, species composition of plant and animal communities. We used geographic information systems, vegetation models, and general circulation models to predict the impact of global climate change (GCC) on the distribution of vegetation at a regional scale, the state of Texas. Then we used habitat preferences for species of rodents in the state to predict how GCC would impact their geographic range and species richness. Our determination of suitable habitats for species of rodents included an average of 98% of capture points, and we found that suitable habitat averaged 62% of the geographic range of species. Size of habitat-corrected range increased an average of 2- to 3-fold under GCC, indicating that rodents were more adaptable to changes in vegetation than were other mammals we studied (e.g., lagomorphs and insectivores), whose range decreased, but similar to Chiroptera, whose ranges also increased. Geographic ranges shifted an average of 54% under a warmer, wetter climate and 61% under a warmer, drier climate, resulting in inclusion of an average of 60% new vegetation associations in the ranges under the former scenario and 64% under the latter scenario. The impact of GCC on rodents in Texas was greatest under the warmer, drier climatic scenario. Two species, Oryzomys cousei and Microtus mexicanus, were predicted to go extinct because their suitable habitats did not occur under GCC. These results demonstrated that the type of climate change (warmer, drier or warmer, wetter) and its severity would be important. GCC was predicted to have the greatest impact on rodent distributions in eastern Texas under a scenario of a warmer and wetter climate because forests expanded, whereas the impact would be greatest in western and southern Texas if climate becomes warmer and drier because desert and shrub habitats expanded. Life-history variables (e.g., habitat type or diet) were correlated with changes in size of range, location, or habitat composition, and reflected broad changes in the relative distribution of vegetation types. Granivores and herbivores used fewer new habitat associations that entered Texas after GCC than did omnivores or insectivores, as did terrestrial rodents compared with fossorial or arboreal rodents.

We investigated fungal consumption and resulting patterns of potential spore dispersal by 6 small mammals in old-growth habitat in the Sierra Nevada of the United States, a region in which this ecological interrelationship is poorly understood. Small mammals consumed a wide array of food items, although only feces of northern flying squirrels (Glaucomys sabrinus), golden-mantled ground squirrels (Spermophilus lateralis), and Douglas squirrels (Tamiasciurus douglassi) frequently contained spores of hypogeous fungi, whereas those of lodgepole chipmunks (Tamias speciosus), long-eared chipmunks (T. quadrimaculatus), and deer mice (Peromyscus maniculatus) did so rarely. Feces from the 3 squirrel species also contained a greater number of hypogeous fungal genera per sample than did samples from the latter 3 species. Flying squirrels potentially dispersed the greatest variety of ectomycorrhizal fungi (16 genera): 8 in spring and 15 in autumn. Frequency of occurrence of 9 genera in the feces of flying squirrels differed between spring and autumn. Interspecific differences in patterns of fungal consumption, coupled with differences among these small mammals in habitat use, mobility, and digestive physiology, suggest that these small mammals may disperse fungi in ecologically nonredundant ways and that the integrity of entire small-mammal communities may be important to the maintenance of ectomycorrhizal diversity in coniferous forests.

The suckling behavior of some mammals is characterized by preferences for anterior or posterior nipples and consistent return by individual young to particular nipples or nipple pairs. Some murid species also display tenacious nipple attachment. Pine voles (= woodland voles, Microtus pinetorum) have tenaciously clinging young and 2 pairs of abdominal mammae. We examined whether young pine voles preferred particular nipple pairs and whether young on the 2 pairs were differentially groomed or dislodged by their mothers. We also examined whether young showed fidelity to suckling location. Young pine voles preferred the hindmost nipples and were dislodged less frequently from those nipples than from the more anterior pair. We found no evidence that mothers differentially groomed young on the 2 pairs. Fidelity to nipple and nipple pair was greater in small than in large litters, which may reflect less competition for hind nipples in small litters and the need to consistently stimulate a nipple to ensure productivity.

The annual reproductive cycle of adult male Formosan wood mice (Apodemus semotus) collected monthly from the Alishan area, Taiwan, was investigated. Mean monthly body mass varied between 25.0 g ± 0.8 SE and 27.1 ± 1.3 g and did not show significant seasonal change. Mass of reproductive organs, spermatogenic activity, and levels of testicular and plasma androgen exhibited a distinct pattern of seasonal change. Testes, epididymides, and seminal vesicles were lightest and spermatogenesis was virtually arrested in January and December. For the remainder of year, all animals examined were spermatogenically active. However, spermatogenic activity was most intense and reproductive organs were heaviest in March–April and August–September. A decline occurred in mass of reproductive organs and diameter of seminiferous tubules in May–July, but spermatogenesis was unaffected qualitatively. Levels of testicular and plasma androgen were elevated in March–April and August–September, coinciding with periods of intense spermatogenic activity and the heaviest reproductive organs and were significantly correlated with mass of testes, epididymides, and seminal vesicles, and diameter of seminiferous tubules. Day length and temperature, but not precipitation, were correlated with mass of testes, epididymides, and seminal vesicles. This is the 1st study to investigate seasonal patterns of androgen levels in plasma and testes in the genus Apodemus.

The energetics of 5 species of the flying fox genus Pteropus were measured with respect to ambient temperature. These data and those from 2 species in the literature were examined in relation to body size and to their distribution on continents or small islands. Log₁₀ body mass accounted for 94% of the variation in log₁₀ basal rate of metabolism of those 7 species. Females belonging to large species of Pteropus were smaller than conspecific males and consequently had lower (total) basal rates than males. No factor other than body mass in this analysis was correlated with basal rate in Pteropus. However, in the context of 21 species of pteropodids, continental Pteropus have basal rates that are 28% greater than small-island endemics. The effect of island size was not demonstrated in Pteropus, when examined alone, because the smallest species studied are small-island specialists, and the largest species live on continents, which means that effects of mass and island size are confounded, which leads to a high scaling power (1.06) for basal rate in this genus. Log₁₀ thermal conductance in Pteropus increased with log₁₀ body mass, 5 species having low thermal conductances by mammalian standards. Body temperature was independent of body mass.

We compared 2 bat detecting systems that use condenser microphones, 1 that performed computer analysis (Anabat6) of the output of a zero-crossing period meter (Anabat system) and the other that performed computer analysis (Canary 1.2) of the output of slowed-down (= time-expanded) recordings (Racal system). The 2 systems provided significantly different pictures of both numbers and characteristics (highest frequency, lowest frequency, and duration) of echolocation calls, whether recorded from free-flying bats in the field or from a stationary bat in the laboratory. Although the AnabatII detector was slightly more sensitive than the QMC S200 detector, the Racal system detected more echolocation calls than the Anabat system; the 19-dB difference in sensitivity was associated with a zero-crossing period meter in the Anabat system. Results suggest 2 recommendations. First, that analysis using zero-crossing period meters should not be used to describe echolocation behavior or calls of bats. Second, that studies of activity and use of habitat based on analysis using zero-crossing period meters should involve calibration against more sensitive bat-detecting systems.

Although echolocation calls of most bats exhibit species-specific characteristics, intraspecific variation can obscure differences among species and make reliable acoustic identification difficult. We examined levels of intraspecific variation in search-phase calls of 7 species of vespertilionid bats from several locations in the eastern and central United States. Echolocation calls were recorded from light-tagged bats using the Anabat II detector and associated software. Analook software was used to calculate values for 5 parameters of calls: duration, maximum frequency, minimum frequency, frequency of the body, and slope of the body. Analysis of our results indicates that most intraspecific variability in calls was attributable to differences among individuals and within individual call sequences. Observed levels of geographic variation, although significant in all species examined, were comparatively small and showed no trends among areas. We include a preliminary description of variability in echolocation calls of Nyticeius humeralis and Myotis leibii.

Bats are known to use areas above perennial streams and rivers for foraging and traveling; however, little is known about bat use of smaller streams that flow intermittently. We compared bat activity among 3 size classes of streams and upland sites in a northwestern California watershed during summers 1996 and 1997. Stream size was classified based on channel width. Ultrasonic Anabat II® bat detectors were placed in stream channels and at upland sites, and bat activity was recorded remotely at night. Analysis of bat detector data revealed a significant difference in activity among the 4 habitat types in both years. In 1996, bat activity was greatest along medium and large intermittent streams, was intermediate at small intermittent streams, and was least at upland sites. In 1997, a similar pattern was found, but no significant difference was found in bat activity between small stream and upland sites. To determine species presence, bats were captured in mist nets at stream sites with the highest bat activity. Results are presented indicating differences in number of captures by species between medium and large streams.

Intrageneric relationships within Noctilio were examined using the entire 1,140 base pairs of the mitochondrial cytochrome-b gene and 1,398 base pairs of the nuclear recombination activating gene-2. Sequences were analyzed to establish the relative time frame during which piscivory, the feeding strategy for hunting and eating fish, evolved in this genus. Piscivory represents the derived morphologic state for the genus Noctilio, and N. leporinus evolved from a N. albiventris-like ancestor. Distance values for specimens of N. leporinus from the Antilles, Central America, and South America suggest that N. leporinus speciated recently, 0.28–0.7 million years ago. Within N. albiventris, evidence exists that specimens from Peru diverged 1.16–2.9 million years ago. Analysis of these data suggests the possibility that 2 biological species are present within N. albiventris.

We document the known distribution of Molossus bondae as far south as northern Argentina. Argentine specimens include the type series of M. obscurus currentium Thomas, 1901, a name with priority over M. bondae. Analysis of morphometric variation across the species' geographic range revealed the presence of 3 distinct populations of M. bondae. We reassessed taxonomic and nomenclatural status of populations previously included under the name M. bondae and concluded that the valid name for this taxon is Molossus currentium Thomas. Based on 12 cranial and 2 external characters we recognize 3 subspecies for this species, 1 of which we formally describe as new.

Sixteen populations of Peromyscus on islands in the Sea of Cortéz (= Gulf of California), Mexico, were compared with 9 mainland species of Peromyscus based on sequence data for a 699-base-pair fragment of the mitochondrial DNA (mtDNA) COIII gene. An unrooted neighbor-joining tree based on corrected pairwise estimates of sequence divergence among variable mtDNA haplotypes indicated a recent (late Pleistocene) origin from a source on the adjacent mainland for 10 island forms representing P. boylii, P. crinitus, P. eremicus, P. eva, P. fraterculus, and P. maniculatus. Five other populations did not seem to be derived from species currently on the nearest mainland, suggesting overwater dispersal or distributional changes on the mainland after drowning of land-bridge connections. One population, possibly of more ancient origin, on Isla Cerralvo near the Baja California peninsula, probably originated via trans-Gulf rafting from the Sonoran mainland. Based on these results, 4 insular species (P. stephani, P. interparietalis, P. caniceps, and P. dickeyi) should be considered subspecies of P. boylii, P. eremicus, P. fraterculus, and P. merriami, respectively. The emergent view of evolutionary relationships within the subgenus Haplomylomys in the region reflects pre-Pleistocene phylogeographic events on the mainland surrounding the Gulf and a more recent origin of island populations.

Phylogenetic relationships among 4 subspecies of Neotoma floridana 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 support the recognition of N. f. magister as a distinct species (N. magister). Populations of eastern woodrats from the southern and western United States also possessed relatively high levels of sequence divergence (5.3%), which may be indicative of ongoing divergence between these populations. These findings support conclusions from previous studies and add clarity to the biogeographic processes influencing evolution and diversification of this group of rodents.

Starch gel electrophoresis at 36 presumptive loci was used to study genetic variation and systematic status of 110 wood mice (genus Apodemus) from 19 sites scattered across Anatolia, Armenia, and Iran. Seventeen loci were monomorphic and fixed for the same allele among populations, whereas 19 loci were found to be polymorphic or discriminant among samples. The following species were determined in the material: A. flavicollis, A. uralensis, A. hermonensis, and a taxon provisionally called Apodemus cf. hyrcanicus. The study material was compared with previously analyzed samples from western Anatolia, increasing the total material to 245 specimens from 31 localities. In general, the pattern of variation and level of genetic differentiation within and among species were comparable between western and eastern samples. Intraspecific genetic distances were low, ranging from 0 to 0.051, but interspecific distances were an order of magnitude higher. Similarly, neighbor-joining trees showed negligible differentiation between populations of individual species and no sign of intraspecific structuring. A. uralensis seems to prefer humid sites, whereas A. hermonensis and A. flavicollis also occur in drier places. Individuals referred to Apodemus cf. hyrcanicus were limited to lowlands south of the Caspian Sea. Problems associated with the systematic relationships and taxonomy of A. falzfeini–fulvipectus–hermonensis–arianus and A. cf. hyrcanicus from northern Iran are briefly discussed.

We studied characteristics of paired antlers, including types of asymmetry, from 1,501 Alaskan moose (Alces alces gigas). We observed no evidence of antisymmetry in moose antlers, but number of tines was greater on left than right antlers, indicating directional asymmetry. Absolute and relative fluctuating asymmetry (FA) occurred for palm characteristics but not for beam circumference. Relative FA varied inversely with the overall size of antlers for attributes of the palm, which was expected for a secondary sexual characteristic. Smaller-antlered males exhibited greater FA than did larger-antlered moose in palm characteristics. Because large-antlered males, which mate most often among moose and other polygynous cervids, expressed the least relative FA, we hypothesize that this metric indicates quality of individual moose. Whether symmetry of antlers is related to antler breakage or honest advertisement or whether females select mates based on FA is unknown and deserves additional study.

Few studies of sexual segregation in ruminants have tested widely invoked mechanisms of segregation in mixed-sex groups. In a sexually segregated population of Roosevelt elk (Cervus elaphus roosevelti), we examined if adult males had reduced intake of forage when in mixed-sex groups and if intersexual differences in aggression caused females to avoid males. Based on a mechanistic model of forage intake, animals with lower instantaneous feed intake should have higher cropping rates. Focal animal sampling indicated that adult males and females in summer and winter had similar cropping rates in mixed-sex groups, whereas males in male-only groups had lower rates of cropping than males in mixed-sex groups. Outside the mating season, males in male groups spent proportionally less time ≤1 body length of congenders than females in female groups, and the rate of aggression ≤1 body length was higher for males. Female–female aggression was higher in mixed-sex groups that contained more males than the median proportion of males in mixed-sex groups. Female and mixed-sex groups walked away when groups of males numbering >6 were ≤50 m but did not walk away when male groups ≤50 m had ≤5 individuals. Sexual segregation was associated with behaviors of sexes in mixed-sex groups: reduced intake of forage by males and increased female–female aggression with more males.

From 1995 to 1999, we conducted an ecological study of thamin (Cervus eldi thamin) at Chatthin Wildlife Sanctuary in central Myanmar; we maintained records on deer sightings and radiotracked 11 adult male and 8 adult female deer. Based on 747 sightings, a 0.63:1.0 adult male : female ratio and 0.51:1.0 fawn : adult female ratio were observed. Mean group size was variable (1.0–5.9 deer) and showed seasonal differences, with few groups observed in August–September and groups of ≤70 individuals observed in March–April. Based on the fixed-kernel method, annual home range was 9.04 km² ± 5.67 SD and 7.25 km² ± 3.45 SD for males and females, respectively. Thamin increased their seasonal home range during the hot–dry season, possibly in response to decreased forage and water availability and increased mating activity. The observed synchrony of estrous onset (March–April) and fawning (October–November) in female thamin is unusual for a tropical cervid species, but reproductive seasonality appears timed to balance fawn survival with doe nutrition in a monsoon environment.

We monitored use of plants and habitat in a population of thamin (Cervis eldi thamin) in Chatthin Wildlife Sanctuary in central Myanmar from 1996 through 1999. Habitat use within the deciduous dipterocarp forest was monitored by radiotracking 19 individuals during daylight hours and conducting biannual fecal pellet surveys along 87 km of marked transects. Habitat abundance was determined by classifying a LANDSAT image of the region, collecting vegetation parameters at 201 plots located within the sanctuary, and pacing habitat types along marked transects. Thamin consumed primarily forbs, grasses, and agricultural crops but also fruits of 8 common tree species. Thamin used dipterocarp forest habitat but showed some seasonal shifts and distinct individual differences in habitat use. Except during of the mating season (January–April), females were found more often in degraded forests and closer to crops than males. Sex differences in habitat selection were due to either female selection of habitats with lower predation risk or increased nutritional needs associated with lactation.

We used 11 microsatellites, highly variable nuclear markers, to infer kinship among 35 San Joaquin kit foxes,Vulpes macrotis mutica, and combined this information with field observations to gain insight into fox social behavior. Fox social units consisted of solitary foxes, mated male–female pairs, and trios consisting of a mated pair plus another adult. Pair-mates were not closely related. The additional adult (1 male, 1 female) in 2 trios was the offspring of at least 1 of the pair-mates. Foxes living on adjacent home ranges tended to be more closely related than foxes that did not live on adjacent home ranges, largely because females on adjacent home ranges were often closely related. F_IS values indicated a deficiency of homozygotes that was likely due to clusters of relatives living on adjacent home ranges. Foxes that shared the same den on the same day were usually members of the same social group. Contrary to expectations, however, we sometimes found foxes sharing dens with foxes from other social groups. Many cases involved unpaired individuals and appeared to be unsuccessful attempts at pair formation. Other cases involved members of 2 adjacent social groups, a pair and a trio. Both members of the pair were closely related to ≥1 member of the trio, indicating that kit foxes can maintain enduring social relationships with adult offspring or siblings that have dispersed to a new home range and found a mate.

We collected information on the movement patterns of wolves (Canis lupus) captured within a 30,000-km² area in the Northwest Territories and western Nunavut. Currently, diamond mining and road construction are occurring in the area used by these migratory wolves for denning. During summers of 1997 and 1998, 23 wolves in 19 different packs were captured and fitted with collar-mounted satellite transmitters. Areas used by these wolves varied seasonally and seemed to correspond to movements of migratory caribou (Rangifer tarandus). Annual home-range sizes (95% minimum convex polygon), averaged 63,058 km² ± 12,836 SE for males and 44,936 ± 7,564 km² for females. Wolves began to restrict movements around a den site on the tundra by late April. They did not depart from their summer ranges until late October, after which they followed caribou to their wintering grounds. Straight-line distances from the most distant location on the winter range to the den site averaged 508 ± 26 km during 1997–1998 and 265 ± 15 km in 1998–1999 (P < 0.01). Home range in summer averaged 2,022 ± 659 km² for males and 1,130 ± 251 km² for females. No difference was detected between sexes or years. All but 2 of 15 wolves returned to <25 km of a previous den, and 2 wolves returned to the same den site. We believe that human activities that disturb or displace denning wolves, or that alter the distribution or timing of caribou movements, will have negative affects on reproductive success of wolves.

Bacular development is described for the Weddell seal, Leptonychotes weddelli, based on specimens from 1 to 18 years of age. The bacular apex, cross-sectional configuration of the shaft, base, and other aspects are described and compared with other genera of phocids. The anterior dorsal aspect of the baculum of Leptonychotes is unique among phocids in development of a pronounced crest as an adult.