Large-scale ecological patterns emerge from multiple biological processes that interact on several scales and are affected by the heterogeneity of the environment. I use a landscape simulation model to explore and analyze how interactions among various ecological processes affect patterns of mammalian species diversity according to body size. The model incorporates ecological realism by using mammalian allometric relationships with realistic values taken from field data. It uses energy as a common currency to model and compare how species of different sizes use their environment. Components of the model include landscape, habitat, patch, community, species, and population. Processes include continuous-time population growth, saturation effect, species–habitat matching, demographic stochasticity (local-scale), dispersal, and catastrophic stochasticity (landscape-scale). I simulated a 16-patch landscape, with each patch having a unique habitat, and a 10-species pool in which species differ only in body size. Summed over the landscape, a log-normal relationship between body size and species abundance emerges. Additionally, geographic range increases nonlinearly with the log of body size. These patterns are qualitatively consistent with patterns of mammalian species diversity observed in natural systems, suggesting that they can emerge from scaling of habitat use with body size. I also simulated a simple 4-patch landscape, with each patch having a unique habitat, and a 26-species pool to draw from in which species differ only in body size. The results show that interspecific competition by itself reduces species diversity in each habitat and in the entire landscape. Stochasticity depresses mean population sizes but opens opportunities for species to avoid competitive exclusion. It also allows different habitats to have different communities that are characterized by the consequences of which large species become locally extinct at random. Demographic and catastrophic stochasticities differ, however, in their characteristic effects on species diversity. These characteristic effects can be used as fingerprints to identify processes acting in nature. Dispersing individuals move between habitats and reestablish the local populations of their species. Overall, the model provides us with predictions of how process-interactions in heterogeneous landscape may affect species composition and community structure.

Corridor effects on population densities and habitat use of 3 small-mammal species were assessed during 1998–2000 in an experimentally fragmented landscape. Corridor presence did not have a statistically significant effect on population densities of cotton rats (Sigmodon hispidus) or cotton mice (Peromyscus gossypinus); however, a significant effect was observed for old-field mice (Peromyscus polionotus) during 2000. Cotton rats were captured more frequently than expected in corridors, while old-field mice were captured more frequently than expected in habitat-patch interior; and cotton mice exhibited a more uniform distribution across habitat types. These results suggest that landscape fragmentation and habitat structure may have varying effects on population densities of different species.

The European rabbit (Oryctolagus cuniculus) is a key prey species in Mediterranean ecosystems and is ecologically plastic. However, ecological responses of rabbits to different habitats are poorly understood. We present data on abundance, distribution, activity, and survival in 3 neighboring habitats in southwestern Spain differing in refuge and forage availability. Scrubland presents dense cover but low forage abundance; grassland offers little protective vegetation but high food availability; the ecotone provides intermediate levels of both resources. Rabbits reached the highest abundance in ecotone, whereas low food and refuge availability seemed to limit their abundance in scrubland and grassland, respectively. In scrubland, rabbits were dispersed among the cover. In grassland, rabbits were linked to aggregated burrows. In ecotone, rabbits dug burrows in the bordering bushes that abutted grassy feeding pasture. Predation by raptors was low in scrubland, and mortality due to mammalian carnivores was higher in spite of more diurnal rabbit activity. Carnivore predation also caused higher mortality in grassland, where rabbits were more nocturnal. In ecotone, the effect of both mammalian carnivores and raptors on rabbits was similar. Mortality by disease seemed to be linked to level of rabbit aggregation.

We conducted exploratory analyses to examine the relative roles played by natural and anthropogenic influences on persistence of a montane mammal. We revisited historical locations of pikas (Ochotona princeps) within the hydrographic Great Basin during summers of 1994–1999. Seven of 25 populations (28%) reported earlier in the 20th century appeared to have experienced recent extirpations. We assessed causative agents of faunal change using several alternative, but not mutually exclusive, hypotheses. Higher probability of persistence was correlated with greater area of talus habitat at local and mountain-range scales, higher elevation, more easterly longitude, more southern latitude, lack of livestock grazing, greater distance to primary roads, and wilderness management. However, only area of habitat in the mountain range, maximum elevation of talus habitat, and distance to primary roads appeared in the most parsimonious model of persistence when we used Akaike's information criterion model-selection technique. These results suggest that relaxation of montane faunas may occur more rapidly than previously expected; that biogeographic models of species occurrence can be refined by including more proximate factors (e.g., grazing status, proximity to roads); and that habitat-based approaches to modelling vertebrate trends should be accompanied by field data because population loss can occur with no apparent change in habitat.

Sea otter (Enhydra lutris) populations were exploited to near extinction and began to recover after the cessation of commercial hunting in 1911. Remnant colonies of sea otters in the Aleutian archipelago were among the first to recover; they continued to increase through the 1980s but declined abruptly during the 1990s. We conducted an aerial survey of the Aleutian archipelago in 2000 and compared results with similar surveys conducted in 1965 and 1992. The number of sea otters counted decreased by 75% between 1965 and 2000; 88% for islands at equilibrial density in 1965. The population decline likely began in the mid-1980s and declined at a rate of 17.5%/year in the 1990s. The minimal population estimate was 8,742 sea otters in 2000. The population declined to a uniformly low density in the archipelago, suggesting a common and geographically widespread cause. These data are in general agreement with the hypothesis of increased predation on sea otters. These data chronicle one of the most widespread and precipitous population declines for a mammalian carnivore in recorded history.

We use a multistate mark–recapture model incorporating information on body mass, sex, time of capture, and natal colony to estimate the probabilities of survival, capture, and mass-state transition of New Zealand fur seal (Arctocephalus forsteri) pups from 3 sites (colonies) on Otago Peninsula, South Island, New Zealand. Apparent survival for a mean sampling interval of 47 days was high (≥0.850) after correcting for tag loss, and there was evidence that there were differences between sexes and among sites even after controlling for mass at capture. Survival did not differ among body-mass classes. Heavier pups had lower capture probabilities; however, differences in mass adequately explained any potential differences in capture probability due to sex. State-transition probabilities among mass classes also differed with time of capture, and between sexes and among sites. Although bias in estimates of survival probability is minimal when survival is high, heterogeneity in capture probabilities among different classes of individuals can bias estimates of pup growth rate and sex ratio. We recommend measuring mass of individuals and incorporating this and perhaps other pertinent information into multistate mark–recapture models when attempting to estimate survival and to determine the effect of capture probability on estimates of other life-history parameters.

We evaluated size of home ranges for male and female black bears (Ursus americanus) at 3 study sites in Washington to determine whether home-range sizes differed between sexes, study sites, and objectives of forest management. Vegetative conditions differed among study sites as a result of differences in mean annual precipitation (52, 200, and 380 cm/year) and forest management practices. We analyzed ranked proportions of forest-cover types within error polygons for telemetry locations as measures of use, interspersion, and juxtaposition of cover types and compared these with ranks of cover types available within composite home ranges for all bears in each study site and with those available within adaptive-kernel home ranges for individual bears. Fixed-kernel estimates of home ranges for males were 3.8 times larger than those for females. Home-range size for females differed (P = 0.04) between study sites but home-range size for males did not (P = 0.79). In the study site with intensively managed and relatively undisturbed forestlands, home ranges for females were of similar size. Males and females occupied cover types different from that available within study sites and within individual home ranges. Differences among study sites for home-range sizes for females may be correlated to differences in available forage plants and cover, which may be explained by differences in annual precipitation. Behavioral differences for males and females, too, may explain differential use of forest-cover types. Hence, differences in home-range sizes between males and females and among regions may result, in part, from climatic and vegetative conditions, as well as from social status.

The wolverine (Gulo gulo) is an uncommon, wide-ranging carnivore of conservation concern. We evaluated performance of landscape models for wolverines within their historical range at 2 scales in the interior Northwest based on recent observations (n = 421) from Washington, Oregon, Idaho, and Montana. At the subbasin scale, simple overlays of habitat and road-density classes were effective in predicting observations of wolverines. At the watershed scale, we used a Bayesian belief network model to provide spatially explicit estimates of relative habitat capability. The model has 3 inputs: amount of habitat, human population density, and road density. At both scales, the best models revealed strong correspondence between means of predicted counts of wolverines and means of observed counts (P < 0.001). Our results can be used to guide regional conservation planning for this elusive animal.

We used stable carbon and nitrogen isotope analyses to test the hypothesis that nectar-feeding bats Leptonycteris curasoae and Glossophaga longirostris depend on cacti and agaves as food sources in Venezuelan arid zones and to compare their trophic positions. We measured the isotopic compositions of muscle tissue in the 2 species during 1 year at 3 arid locations. Overall carbon isotopic composition (∂¹³C) of L. curasoae (−11.76‰) and G. longirostris (−13.28‰) resembled values characteristic of columnar cacti and agaves (−12.47‰), which have in common the crassulacean acid metabolism (CAM) photosynthetic pathway. L. curasoae appears to be more dependent on cacti and agaves (98% CAM in the diet) than G. longirostris (85% CAM in the diet). CAM dependence, as we designate dependence on cacti and agaves, was evidenced across sites. Level of CAM dependence slightly varied over the year only in G. longirostris. We concluded that the 2 species of bats mainly rely on CAM plants in Venezuelan arid zones. Overall nitrogen isotopic composition (∂¹⁵N) did not differ between L. curasoae (15.87‰) and G. longirostris (15.37‰). Although our results suggest that the 2 bats occupy the same trophic position, no conclusive evidence supported this observation. The strong interdependence between these bats and their host CAM plants in northern South America suggests that a disturbance affecting 1 component of the interaction would have a strong effect on the other.

Specimens may pose a risk to personnel handling them such as the radioactive fauna collected from contaminated areas in Chornobyl. To minimize radiation exposure and to evaluate an inexpensive molecular tool in identifying species of shrew, we analyzed DNA sequences from the cytochrome-b gene. Specimens were visually identified as Sorex araneus, S. minutus, and Neomys fodiens, and morphological variants were noted that could represent additional species. Cytochrome-b sequences indicated the apparent variants represented intraspecific polymorphisms. This approach substantially reduced exposure to radioactivity present in the archived material. Excluding salaries and cost of equipment, the analytical cost per specimen was US$9.00. The benefit and accuracy in identifying specimens this way is justified based on the reduction of risk these samples may pose.

A polymerase chain reaction–based method was developed for gender determination in a wide variety of marine and terrestrial mammals, including cetaceans, pinnipeds, ungulates, canids, and ursids. An intron within the zinc-finger x (Zfx) and zinc-finger y (Zfy) genes was amplified. Size variation between the Zfx and Zfy introns results in a Y-specific band in males. Size of the Zfy intron varies more across species than that of the Zfx intron. This technique is simple and rapid, requires small amounts of DNA, and can be applied to a variety of mammalian species. In contrast to previous methods, only 1 primer set is needed for both gender determination and internal verification of amplification.

To assess genic differentiation and phylogenetic relationships among selected species in the subgenus Aporodon, we screened 31 presumptive genetic loci in 6 species in the subgenus Aporodon (R. creper, R. gracilis, R. mexicanus, R. microdon, R. spectabilis, and R. tenuirostris) and in 4 species in the subgenus Reithrodontomys (R. chrysopsis, R. fulvescens, R. megalotis, and R. sumichrasti). The resulting phylogenetic trees were compared with the results of previous molecular and morphological studies. Results demonstrate that the subgenus Aporodon is monophyletic. Relationships determined on the basis of allozymes are largely congruent with an earlier analysis based on morphological and molecular characters. However, samples of R. mexicanus do not form a monophyletic lineage. Accordingly, populations from north-central Oaxaca and Costa Rica each likely represent an undescribed species.

Phylogenetic relationships among 8 members of the Sorex cinereus group (S. camtschatica, S. cinereus, S. haydeni, S. jacksoni, S. portenkoi, S. preblei, S. pribilofensis, and S. ugyunak) and S. longirostris were estimated using DNA sequence data from 2 mitochondrial genes, cytochrome b (1,140 base pairs) and nicotinamide adenine dinucleotide dehydrogenase 4 (582 base pairs). S. hoyi, S. monticolus, S. palustris, S. tenellus, S. trowbridgii, and S. vagrans also were included in our analyses. Phylogenetic analyses of the combined data recovered 2 major clades within the species group: a northern clade that includes the Beringian species (S. camtschatica, S. jacksoni, S. portenkoi, S. pribilofensis, and S. ugyunak), S. haydeni, and S. preblei and a southern clade that includes S. cinereus and S. longirostris. Mitochondrial DNA clades generally corresponded to previously identified morphological groups with 2 exceptions: inclusion of S. longirostris with S. cinereus in the southern clade and inclusion of S. preblei within the northern clade. With the exception of the 5 Beringian species, taxa were readily differentiated with strong bootstrap support in our topologies. We also noted phylogenetic concordance with the general ecological affiliations of each species; the northern clade generally includes xeric-affiliated species, whereas the southern clade includes species with mesic habitat affinities.

The taxonomic status of white-backed hog-nosed skunks (genus Conepatus, subgenus Oryctogale) was examined using external and cranial morphology as well as mitochondrial deoxyribonucleic acid sequence. Two species, Conepatus leuconotus and C. mesoleucus, and their subspecies were determined to represent only a single species, C. leuconotus. Within this species there are 3 management units, or subspecies, recognized conservatively. These subspecies are C. l. leuconotus (including C. l. texensis, C. m. mearnsi, C. m. mesoleucus, C. m. nelsoni, C. m. venaticus, C. m. nicaraguae, C. m. sonoriensis, and C. m. filipensis); C. l. figginsi (=C. m. figginsi and including C. m. fremonti); and C. l. telmalestes (=C. m. telmalestes). In the case of C. l. figginsi and C. l. telmalestes, further genetic research may indicate that these taxa are not valid, but the populations that they represent (if not extinct) will require different management strategies from the wide-ranging C. l. leuconotus.

Temporal genetic variation was examined in a coyote (Canis latrans) population that experienced intensive removal for several decades. The population experienced separate periods of nonselective and selective control, and comparisons were made between control methods. Analyses at 11 microsatellite loci revealed only subtle genetic differences between removal regimes when analyzed by year of birth or resident status. Numbers of alleles per locus (4–16) and expected heterozygosities (0.617–0.915) were high across groups and few 1st-order relatives were detected within groups. Coyote social structure and dispersal patterns appear to adequately maintain genetic variation and promote genetic homogeneity over relatively small geographic scales during periods of locally aggressive removal.

Bullar volume was estimated by external measurements for the subterranean genus Ctenomys (Rodentia, Ctenomyidae) and 24 species of surface-dwelling caviomorphs. Bullae were larger in Ctenomys than in caviomorphs. Larger bullar size may reflect good low-frequency audition and could be an adaptation for subterranean vocal communication. Estimated bullar volume of the Pliocene rodent Actenomys was intermediate between that of Ctenomys and surface-dwelling caviomorphs, in agreement with the presumed intermediate subterranean lifestyle of Actenomys.

Large carnivores that become marauders and man-eaters are frequently thought to be old or infirm, apparently incapable of normal predatory behavior. To evaluate whether this “infirmity theory” offers a general explanation for animal–human conflicts, we examined teeth and jaws of lions (Panthera leo) in museum collections. Although tooth wear and breakage are normal in lions, they are rarely accompanied by severe pathologies. Although the infirmity theory may explain specific instances of carnivore–human conflict, including the infamous case of Tsavo's man-eating lions, most other conflicts can be linked to alternative explanations, especially prey depletion in human-dominated areas, which trigger the opportunity and necessity of exploiting people or livestock (or both) as prey.

Despite their widespread distribution and relative abundance, little is known about the antipredator behavior of agile wallabies (Macropus agilis). The ability to modify time allocation as a function of group size is an antipredator behavior that has been reported in some, but not all, previous studies of members of the genus Macropus. We studied group-size effects and space use for agile wallabies foraging in the open to develop a better understanding of behavior of mid-sized macropods. We found that agile wallabies modified time allocated to foraging and vigilance as a function of group size but were insensitive to distance from cover. We contrast the group size results from agile wallabies with those from other macropodids and speculate that predation by saltwater crocodiles (Crocodylus porosus) may have a profound effect on how agile wallabies perceive and manage predation risk.

We describe design of echolocation signals in 5 species of aerial-hawking insectivorous bats from Malaysia. These bats forage in open spaces above the forest or in large clearings and belong to 2 families: Molossidae (Chaerephon johorensis, Mops mops, Cheiromeles torquatus) and Vespertilionidae (Hesperoptenus blanfordi, Pipistrellus stenopterus). As is typical for aerial-hawking bats, all 5 species produced narrowband calls of long duration (6–21 ms) and low peak frequency (16–44 kHz). However, sequences recorded from bats flying at high altitude (>10 m) were characterized by an alternation between calls that differed in frequency of maximum energy (peak frequency), switching between high- and low-frequency calls. In some species, the types of calls also differed in duration and sound pressure level. We consider possible implications of the alternation of types of calls for the detection of prey in open spaces.

To examine the effects of spatially complex habitat (i.e., cluttered) and prey availability on habitat selection by bats, we constructed 3-dimensional “clutter cones” and monitored activity of free-ranging bats in them. Cones were paired with cones of equal clutter density and size in which we placed ultraviolet (UV) light sources to attract nocturnal insects and hence increase prey availability. We tested predictions arising from resource-partitioning experiments in previous works from laboratories and the field. Activity by bats of all sizes was unaffected by density of clutter, and activity by small-sized bats at all UV-illuminated sites increased significantly, whereas activity by large-sized bats was unaffected. Also, Myotis lucifugus did not negotiate clutter densities as complex as those in previous laboratory work. This suggests that habitat complexity is likely one means by which foraging areas are partitioned between those bats that can exploit them (i.e., smaller species) and those that cannot and that cluttered habitats are avoided except when they may serve a purpose such as an energetic benefit. Although behavioral studies conducted in the laboratory serve to obtain data on ultimate capabilities, differences between results from the laboratory and the field suggest that an animal's behavior may be specific to its present environment.

The feeding ecology of most neotropical bat species is still poorly known, indicating that many complex ecological relationships may be obscured. During a study of bats and their potential role as seed dispersers at the Botanical Garden of Rio de Janeiro, southeastern Brazil, we obtained data on 2 species, Chiroderma doriae and C. villosum, that act as seed predators rather than as seed dispersers. Fecal sample analyses and captive-feeding experiments confirmed this previously undocumented feeding strategy in bats. Both species use a specialized strategy of fig-seed predation, ingesting the rich nutrient content of seeds and discarding most of the coat fragments as compact oral pellets. Evidence from the more abundant C. doriae showed that seeds were consumed in both drier and wetter seasons and by individuals of both sexes, all age classes, and all reproductive stages. Use of seeds, in addition to fruit pulp, probably represents an improvement in the acquisition of nutrients available in figs, showing that the degree of feeding specialization of Chiroderma on this resource may be higher than previous data have shown.

Activities and habitat use of lesser mouse-deer (Tragulus javanicus), a common but poorly studied ruminant native to lowland tropical forests of Southeast Asia, were investigated by full-day radiotracking and direct visual observations in the Kabili-Sepilok Forest Reserve, Sabah, Borneo. The mouse-deer was thought to be nocturnal, but diurnal distance moved per hour and behaviors observed directly in wild mouse-deer indicated that they were mainly active during the day and rested at night. Active individuals foraging or moving from shelter to shelter were mainly observed during the day, and inactive individuals resting on open forest floor were mainly observed during the night. Captive mouse-deer observed in a farm enclosure (1.5 ha in size) also showed activities similar to those observed in the forest. Radiotracking for 24 h revealed that mouse-deer significantly preferred crown-gap areas with dense undergrowth of creeping bamboo (Dinochloa) during the day but that they tended to move to the higher and drier ridge areas at night. These results indicated that mouse-deer used crown-gap areas as foraging sites and ridge areas as resting sites. Our results strongly suggest that mouse-deer use food resources in gap areas in tropical forests.

We studied the influence of human activity, hunting of prey by wolves, reproduction, and weather conditions on daily patterns and duration of activity of 11 radiotracked wolves (Canis lupus) in the Białowieża Forest (Poland) from 1994 to 1999. On average, wolves were active 45.2% ± 0.9 SE of the time and traveled 0.92 ± 0.05 km/h. The mean length of activity bouts was 0.76 ± 0.05 h, whereas inactivity bouts averaged 1.02 ± 0.07 h. Wolves were active throughout the day, but their activity peaked at dawn and dusk, which coincided with periods when they killed most prey. Periods of reproduction and high temperatures had less pronounced effects on activity patterns. Human activity and other factors did not significantly affect the wolves' daily activity patterns. The influence of humans may be indirect if hunting of ungulates by humans modifies activity patterns of the wolves' prey. We conclude that the daily activity patterns of wolves in our study area were mainly shaped by their pattern of hunting prey.

This study presents the first description of social behavior and structure in native populations of the coypu (Myocastor coypus). Data from behavioral observations and trapping were used to describe group composition and behavior at 3 study areas in east-central Argentina in 1999–2000. Seven groups were described (11 coypus/group ± 1.5 SE). Groups were characterized by several adult and subadult females, 1 dominant male, several adult and subadult males, and a variable number of juveniles. Subgroups (mainly composed of juveniles and small adult males) were also identified within some groups. Group fidelity was relatively high. Amicable interactions and cooperative behaviors such as nursing in groups, allogrooming, and alarm calls occurred within groups. Agonistic interactions and marking behavior were rare but suggested that the largest male was socially dominant. This study confirms gregarious habits and a polygynous mating system for the species and provides the first report of the existence of some cooperative behaviors.

Positional behavior of Japanese giant flying squirrels (Petaurista leucogenys) was studied based on 3,318 positional bouts and 2,687 instantaneous samples. Resting, feeding and foraging, locomotion, and grooming were the most common behaviors. The most common locomotor behaviors were leaping, scrambling, walking, bounding, vertical bounding, and gliding. The most common postural behaviors were quadrupedal squatting, hind-limb squatting, vertical clinging, clinging, and crouching. Compared with smaller tree squirrels, Sciurus igniventris and Microsciurus flaviventer, P. leucogenys exhibited a higher frequency of “scrambling” for foraging among terminal branches. The tree squirrels foraged on terminals but fed on larger branches. They also foraged and fed more on vertical surfaces. P. leucogenys spent the most time on small supports, whereas the smallest squirrel (M. flaviventer) spent most on the largest supports.

Ctenomys talarum is a solitary subterranean rodent that maintains exclusive territories by constant movement through a sealed tunnel system. In this study we evaluate the distance traveled in an artificial burrow and maximum natural locomotor speed reached in a 24-h period. Distance moved per day was 179.99 m ± 69.62 SD, and ratio of distance moved to total burrow length was 12.4:1. Maximum locomotor speed was 0.75 m/s ± 0.01 SD. No relationships were found between either distance moved or speed and photoperiod or ambient temperature, and between body mass and distance moved or locomotor speed. Distance moved by C. talarum is related to maintenance of burrow and territorial defense, and locomotor speed, probably, responds to aboveground predation.

Aspects of sexual dimorphism, reproduction, postnatal development, and seasonality of breeding in a solitary bathyergid rodent, the silvery mole-rat (Heliophobius argenteocinereus), as based on a field study in Malawi and on a study of animals kept in a laboratory, are reported here for the 1st time. Sex ratio in all animals (n = 173) did not differ from equality. Wild-captured males were heavier (190 ± 58 g) than females (162 ± 47 g). Mating took place during the cold and dry season (April–July), and births occurred during the hot and dry season (August–October). Mean gestation length was 95 ± 8.5 days, and mean litter size was 3.2 ± 0.9. The altricial neonates weighed 12.8 ± 2.3 g and opened their eyes about 14 days after birth. Postnatal growth rate was slow with a mean growth constant of 0.01 and a mean maximum growth rate of 0.53 g/day. The reproductive biology of H. argenteocinereus reveals characteristics of both social and solitary bathyergids. Thus, parameters believed so far to be typical of social mole-rats, such as long pregnancy and slow postnatal development, can be found in solitary silvery mole-rats as well, calling for a reevaluation of the role of reproductive biology in shaping social life.

We monitored reproduction of 11 female Amur tigers (Panthera tigris altaica) on and near the Sikhote-Alin Biosphere Zapovednik, Russia, 1992–2000, using radiotelemetry, capture, and conventional tracking (using snow and soil substrates). Tigers gave birth in all but 3 months of the year, with a peak in late summer (χ² = 10.68, d.f. = 3, P = 0.014; n = 19 litters from 11 mothers). Minimum age of 1st reproduction for 4 tigers was 4 ± 0.4 years (mean ± 95% confidence interval). Mean interval between litters was 21.4 ± 4.4 months (n = 7 pairs of consecutive litters for 4 tigers). Mean litter size was 2.4 ± 0.6 cubs (n = 16 litters of 9 tigers) when litter size was 1st determined but, due to 41–47% cub mortality (n = 19 litters), decreased to 1.3 ± 0.5 cubs (range = 0–4, n = 19 litters) by the time cubs were 12 months old. At least 57% of cub mortality was anthropogenic. Mean age at dispersal was 18.8 ± 1.5 months (n = 5 litters). Mean reproductive rate was 1.4 cubs/year, but only 0.7 cubs/year survived up to 12 months old. We believe that recent conclusions that tiger populations can grow and recover rapidly from substantial losses may be overly optimistic.

During a 2-year period, radiotelemetry was used to continuously monitor body temperature (T_b) of free-ranging woodchucks (Marmota monax) in southeastern Pennsylvania. Hibernation was preceded by daily T_b fluctuations (“test drops”) of 2–4°C. During hibernation, woodchucks exhibited the characteristic pattern of torpor bouts. Time of arousals occurred randomly, but onset of torpor occurred predominantly between 1800 and 0000 h. Males had shorter hibernation periods (mean of 104.8 days) than did females (121.8 days). Males had shorter torpor bouts, but euthermic bouts were the same length as in females. Males also maintained higher T_b during torpor. Overall, the cost of hibernation was greater for males than for females: males spent 38% more energy than did females. The primary energetic expense for both sexes was the periodic maintenance of euthermy throughout hibernation, which accounted for 75.2% of the energy budget for males and 66.8% for females. Compared with the 1999–2000 hibernation seasons, woodchucks during the 1998–1999 season had longer euthermic bouts, fewer torpor bouts (11.8 compared with 13.1), and spent less time in torpor (68% compared with 75%). These differences conserved more energy during the 1999–2000 hibernation season and may have been the result of severe drought conditions during summer 1999. After emergence from hibernation, woodchucks generally maintained a constant state of euthermy throughout the active season, with T_b fluctuating daily by 1–2°C. However, during the summer drought of 1999, daily T_b fluctuated 8–17°C in 5 of 8 woodchucks, presumably to conserve energy and water.

We analyzed the influence of environmental temperature (open versus shaded habitat) and experimental food availability on surface activity of the degu (Octodon degus), a day-active herbivorous rodent that inhabits central Chile. We manipulated food availability and compared open and shaded study plots to determine the influence of thermal conditions on aboveground activity. Degus displayed a bimodal pattern of daily activity during relatively warmer thermal conditions in the austral autumn, whereas activity was unimodal during colder conditions in winter. However, they had a unimodal activity pattern under warm conditions in the shade when food availability was artificially enhanced in autumn. We observed more animals active in the plots where food was supplemented under all conditions. Our results illustrate spatial and temporal shifts in activity of degus involving a trade-off based on avoidance of exposure to heat and the search for food.