We hypothesized that energy intake of lactating females is the main factor determining growth of the young and that use of maternal energy reserves is less important when food is available in abundance. We studied reproducing female common spiny mouse (Acomys cahirinus) offered millet seeds and water ad libitum. Females gave birth to 1 or 2 young, and growth rate was similar between litters of 1 infant and 2 infants combined. In addition, energy intake of the 2 groups of females was similar. Lactating females increased energy intake by 45% (per g^0.75) over that of nonreproducing females. Energy intake and change in body mass of the lactating female each explained about 50% of the variance in infant growth and, therefore, our hypothesis was not supported. Energy intake and change in body mass of the lactating female together explained approximately 76% of the variance in growth of young.

We studied the use of mineral licks by African elephants (Loxodonta africana) during the dry season in a Kalahari-sand habitat in Hwange National Park, Zimbabwe, to investigate the role of geophagy as a mechanism for supplementing low Na levels in browse and natural water supplies. Plant, water, and soil macrominerals were measured to evaluate mineral availability for elephants during the dry season. Elephant behavior was monitored at licks to investigate the intensity of geophagy (measured by number of mouthfuls of soil consumed) in relation to fecal-Na loss. Female elephants, which probably had greater requirements than did males because of pregnancy and lactation, consumed more mouthfuls of soil and spent a greater part of their activity budget feeding on soil than did males, suggesting that geophagy may be driven by a nutritional requirement. We found the following consistent with the Na -supplementation hypothesis: 1) unlike other minerals, Na in woody plants and natural water supplies may be inadequate to meet the minimum requirements of elephants during the dry season; 2) soils consumed by elephants differed from other soils primarily in their high Na content; 3) intensity of geophagy was negatively correlated with fecal Na ; and 4) elephants in non–Kalahari-sand habitats do not appear to create or use licks, probably because they are able to meet their Na requirements from ubiquitous Na -rich water supplies, which do not occur naturally in Kalahari-sand habitats.

We measured water-influx rate during the hot summer in free-ranging adult Arabian oryxes (Oryx leucoryx) in Mahazat as-Sayd, a 2,244-km² protected area in west-central Saudi Arabia. Oryxes obtained 2,294 ml/day of water in their food and from oxidative water, the latter amounting to 14.2% of total water influx. For ungulates living in hot environments, we constructed an allometric curve: log(water-influx rate [liters/day]) = −0.885 0.922·log(body mass [kg]), (r² = 0.77, F = 26.8, P < 0.001, n = 10). The Arabian oryx had the lowest mass-specific water-influx rate (31.5 ml kg^−0.922 day⁻¹), only 32% that of the camel (99.3 ml kg^−0.922 day⁻¹), emphasizing the degree of evolutionary specialization in oryx. Between June and September, oryxes grazed primarily on 3 grasses, Panicum turgidum, Lasiurus scindicus, and Stipagrostis. P. turgidum, taken in largest quantity, had the highest moisture content, 35–45% per g of wet matter. Dry matter intake averaged about 3.1 kg during the summer months; plant intake varied inversely with moisture content.

The total captive population of the pygmy hippopotamus Hexaprotodon (=Choeropsis) liberiensis has a highly female-biased sex ratio at birth (41% males), which exceeds most of the other known distorted sex ratios in captive mammals. Deviation from an even sex ratio was not compensated by a higher juvenile mortality in females. I examined the possible causes of that deviation and could not find any association between offspring sex and inbreeding, parity, or mother's age. I found, however, a significant difference in sex ratios among different zoological gardens, suggesting that husbandry influenced sex at birth in the pygmy hippopotamus. Further analysis suggested that high feeding intensity and “hands-on” husbandry favored production of daughters. However, not all the observed patterns and relationships could be explained by classic sex ratio theories.

We conducted a study of the effects of horn sizes and trophy hunting on mating behavior and survival of rams in hunted and unhunted populations of Dall sheep (Ovis dalli), Rocky Mountain bighorn (O. canadensis canadensis), and desert bighorn (O. c. nelsoni) sheep. Mating success was positively correlated with horn size in Dall sheep (P = 0.03) and Rocky Mountain bighorns (P = 0.05), but not in the desert bighorn (P > 0.05) taxa. Group sizes, rams per rut group, and competition between rams were lowest in desert bighorn sheep. There were indications of greater harassment of ewes by young rams in trophy-hunted populations. In hunted populations, compared with unhunted, ewes ran away more often from approaching rams, ewes moved farther away from courting young rams (P = 0.003), younger rams performed fewer courtship displays (P = 0.042) and more aggressive displays to ewes, and sheep interacted 27% more of the time. Ram-to-ewe interaction times per individual ewe did not differ for any of the taxa (P > 0.05), and, apparently as a consequence of this, we found no discernable effects of trophy hunting on survivorship of ewes, ewe fecundity, or recruitment of young (P > 0.05). There were greater energy expenditures by young rams in the heavily hunted Dall sheep population versus the paired Dall sheep unhunted population, but not in the lightly hunted Rocky Mountain and desert bighorn populations when compared with unhunted populations. This was consistent with evidence for depressed survivorship of rams too young or too small to be hunted (approximately ages 4–6) in the heavily hunted Dall sheep population (P = 0.0001), but not in the bighorn sheep populations (P > 0.05).

I hypothesize that predation on newborn young represents a seasonal analog to time-lagged predator–prey cycles and can cause directional selection against late birthing. Newborn offspring represent an irruption of vulnerable prey to which predators can respond by adapting their search efforts to find and capture these prey. Those born early would be the 1st to achieve the size or mobility necessary to escape predators. Simple models of predation on moose calves were used to demonstrate how changes in predator efficiency as newborns appear, combined with a short period of offspring vulnerability, would produce selection against late birthing. Of the 9 published studies of mammals, 6 showed evidence of selection against late-born young that could be driven by predation on neonates. If true, this hypothesis has consequences for the way we interpret evidence for “predator swamping” and optimal birthing periods in mammals and other taxa with synchronous reproduction.

We examined the relationship between physical condition and vulnerability to predation in 2 species of mammals having different life history traits. We predicted that predators would be more likely to kill substandard individuals disproportionately in red squirrels (Tamiasciurus hudsonicus) than in snowshoe hares (Lepus americanus), given that sciurids apparently are less susceptible to predation. We also predicted that differences would exist between patterns of substandard-prey selection among groups of predators of red squirrels but not among predators of snowshoe hares because of differential predator efficiencies in capturing elusive prey. Through radio tracking, we found that substandard squirrels (n = 113) were disproportionately vulnerable to predation, whereas hares (n = 125) were killed irrespective of condition. Although the relationship between condition and vulnerability to predation, relative to predator groups, did not differ significantly for either species of prey, the difference was qualitatively greater in squirrels than in hares. These results support the notion that predators are more likely to kill substandard individuals disproportionately when targeting prey species that are difficult to capture and, moreover, that the tendency for particular species of predators to take substandard prey may be a reflection of the predator's hunting strategy and efficiency.

Predicting animal populations over time often is done using models of density–habitat relationships that assume animal density is a reflection of habitat quality. We explored whether this assumption was true for the North American red squirrel (Tamiasciurus hudsonicus), a species present at different densities in 3 conifer habitats: white spruce (Picea glauca; high resource quality, unstable availability), mixed conifer, and lodgepole pine (Pinus contorta; lower resource quality, stable availability). We documented density, body condition, survival, reproduction, and turnover in these 3 habitats during a failure of spruce-cone crop, when the potential for the relative importance of habitats to change was greatest. During this time squirrel densities in white spruce decreased by 66% to match with those found in pine and mixed-conifer forests. Red squirrels in spruce forests experienced lower survival and fewer females successfully weaned young, and juvenile production was lower. Adult and juvenile immigration was more important than local juvenile production in replacing squirrel mortality in spruce and mixed-conifer forests. Our results indicate that density does not always reflect habitat quality for red squirrels, and we question the historical high-quality rating of white spruce habitat for this species. Further, our findings suggest that movement of ostensibly highly territorial adults in late winter and early spring is an important mechanism in determining annual squirrel densities regardless of habitat type.

Adult white-footed mice (Peromyscus leucopus) were more likely to be captured in traps previously occupied by conspecific individuals of the opposite sex than in traps previously occupied by the same sex, especially during breeding season. Sex of a mouse in the 3rd capture by a particular trap appeared related to the sexes of mice in both the 1st and 2nd captures. Breeding females were more likely to be captured in traps previously containing males than nonbreeding females. Breeding individuals occurred more often than expected in traps that previously held other breeding mice of the same sex rather than nonbreeding mice. Captures of juveniles were more likely to follow previous captures of juveniles than of adults, probably because members of the same litter were being captured. Finally, white-footed mice were less likely to be captured in traps that previously held a potential predator, short-tailed shrew (Blarina brevicauda).

Sampling of populations of small mammals has traditionally focused on use of live traps, which are often costly and labor intensive. We tested track tubes as an alternative technique for assessing populations of small mammals. Track tubes record footprints of small mammals and allow determination of their presence or absence without live capture. We compared results from livetrapping against data from track tubes on 5 sites over 1-week periods in June 1999 and June 2000. Correlations between indices of abundance from the 2 techniques were significant in 1999 (r_s = 0.656, P < 0.001) and 2000 (r_s = 0.715, P < 0.001). Using track tubes we distinguished footprints of 4 species. We were not able to distinguish Peromyscus from Clethrionomys gapperi; species of Sorex could not be distinguished. In comparison with livetrapping, track tubes are inexpensive, are much less labor intensive for researchers, and can be run simultaneously on several sites. The technique has good promise where investigators seek only to identify composition and relative abundance of small-mammal species.

The habitat-heterogeneity hypothesis states that an increase in habitat heterogeneity leads to an increase in species diversity. Although community-level analyses of effects of habitat heterogeneity on species diversity are important, they do not reveal the mechanism through which heterogeneity affects diversity. In contrast, habitat associations of particular species suggest a potential mechanism whereby diversity is affected by habitat heterogeneity. The sand–shinnery-oak ecosystem of southwestern United States contains 2 habitat types: blowouts and matrix. Blowouts are small and infrequent wind-formed open patches without shrubs. These disturbances are surrounded by a dense shrub-dominated matrix, mostly containing the low stature oak, Quercus havardii. Habitat associations of particular species with respect to blowouts versus matrix were assessed using capture frequencies and species abundances. Only Dipodomys ordii was more abundant in blowouts than in surrounding matrix, and this only occurred during summer. This seasonal change could be a consequence of competition or predation. All other species showed a preference for the matrix. Considerations of scale and edge effects between blowouts and matrix may provide additional insight into habitat associations of rodents, leading to a deeper understanding of the mechanistic basis of diversity in this ecosystem.

We studied effects of recolonizing wolves (Canis lupus) in the North Fork of the Flathead area of northwestern Montana on the diets of coyotes (C. latrans) from 1994 to 1997. Wolf and coyote diets differed in frequency of occurrence of prey species during 3 of the 4 summers and winters (P < 0.001) during the study. Coyote diets contained more murid prey items, and wolf diets contained more deer (Odocoileus virginianus and O. hemionus) in the summer and elk (Cervus elaphus) in the winter. Coyotes and wolves ate prey of different size during both the summer (P < 0.001) and winter (P < 0.001) months in 1994–1996: wolves took a greater proportion (P < 0.001) of large (>45 kg) prey species and coyotes, small (<2 kg) prey (P < 0.001). Wolves selected a larger proportion of adults (P < 0.001), whereas coyotes selected a larger proportion of juveniles (P < 0.001) during summer. We believe that differential use of food resources facilitates coexistence of wolves and coyotes in the North Fork of the Flathead area.

As income breeders, lactating female bats rely on current resource intake to support costs of reproduction and so must reconcile the conflicting demands of foraging and nursing. We documented changes in the movement of female little brown bats (Myotis lucifugus) around roosts between pregnancy and lactation. Home-range size dropped by 51% between pregnancy and lactation, resulting in a 35% decrease in flight distances. Although pregnant females rarely returned to roosts during the night, lactating females returned 1–2 times, which led to an increase in activity at the roosts beginning about 3 h after initial emergence. We argue that their high mass-specific milk production forces lactating females to nurse at night, which in turn imposes a constraint on foraging distances. The shift to a smaller home range is probably facilitated by the concomitant increase in insect biomass during the July lactation period.

During the 5-month dry season, I studied the community structure of bats in the Neotropical savanna of Espíritu, Bolivia. This seasonally inundated, grassland-dominated savanna is inhabited by ≥38 species of bats, and diversity is high (H′ = 2.88). Species richness is highest in forest islands (26 species), open woodlands and gallery forests (11 species each), and dense thorny bushes (7 species) and less in other plant associations. Although species from almost all trophic guilds filled by New World bats occur in the area, small medium-size low-flying insectivorous species and medium-to-large fruit-eating bats predominate.

Changes in body mass, length of forearm, and length of total epiphyseal gaps of young Formosan leaf-nosed bats (Hipposideros terasensis) were monitored by marking and recapturing at a maternity colony in central Taiwan. Length of forearm and body mass of 1-day-old neonates averaged 43.3 mm ± 2.7 SD and 15.9 g ± 3.3 SD, respectively. Increase in forearm length and body mass was fastest in the 1st week after birth, but rate of increase decreased thereafter. Length of total epiphyseal gap increased to its maximum size at about 10 days after birth and subsequently decreased linearly. Growth constants derived from the logistic growth model were 0.096 and 0.114 for the increase in length of forearm and body mass, respectively. Age of H. terasensis between 1 and 44 days can be estimated either by length of forearm when forearm length is ≤91 mm or by length of total epiphyseal gap when forearm length is >91 mm. Subsequent monitoring suggested that males of H. terasensis are capable of reaching sexual maturity in their 1st year and females in their 2nd year. When compared with other bats, growth rate of H. terasensis was faster than that of many tropical species but slower than that of most temperate species.

I measured nocturnal activity of 37 New Zealand long-tailed bats (Chalinolobus tuberculatus) during pregnancy, lactation, and postlactation. Availability of flying insects peaked during lactation. C. tuberculatus was active throughout the night, making 4.0 ± 0.2 SE foraging bouts interspersed with roosting periods. Bats were active for 71.3 ± 1.6% of the night (354 ± 10.6 min). The first foraging bout was significantly longer than later bouts, but length of roosting bouts did not vary. Bats returned to the vicinity of their day colonies to roost at night. Ambient air temperature (3–21°C) had little influence on duration of activity. Length of active periods did not differ among reproductive females, nonreproductive females, and adult males. Reproductive females were active for significantly longer periods during lactation than during pregnancy, but not after lactation. I predict few differences between reproductive classes because energy demands are high throughout the reproductive cycle, females have different mechanisms (such as increasing foraging efficiency, using torpor, and selecting thermally beneficial roosts) for balancing high energy requirements, and energy demands limit all classes in a cold temperate climate when food is in short supply.

We compared microwear from shearing facets of lower molars from Parascalops breweri (the hairy-tailed mole) and Scapanus orarius (the coast mole) with that from other small mammal species including a tenrec, a hedgehog, 3 primates, and 2 bats. The 2 mole species exhibit a distinct microwear pattern that is characterized by many short, narrow scratches, and relatively few pits. Although the molars of the streaked tenrec (Hemicentetes nigriceps) differ profoundly in morphology from those of moles, they show a very similar pattern of microwear on their shearing facets. This common pattern (missing in the rest of the comparison sample) is likely a product of the importance of earthworms in the diets of both H. nigriceps and the moles and is plausibly explained by the interaction between teeth and soil from the inside and outside of earthworms. These results may be useful in interpreting microwear patterns in fossil mammals.

Genetic diversity and gene flow were examined within and among populations of nine-banded armadillos (Dasypus novemcinctus) from Paraguay. Although D. novemcinctus is hunted regularly and constitutes an important protein resource in Paraguay, no conservation or management program exists for this species. To contribute toward conservation planning for this species, we examined intra- and interpopulation DNA sequence variation in the mitochondrial cytochrome-b gene from 75 specimens representing 5 populations from Paraguay. Twenty-five haplotypes were identified among the 75 individuals examined. Haplotype diversity (h) and nucleotide diversity (π) ranged from 0.68 to 0.94 and 0.003 to 0.005, respectively. Although genetic homogeneity was observed among all 5 populations, nested-clade analysis revealed continuous range expansion, isolation by distance, and long-distance dispersal of female nine-banded armadillos.

A new species in the genus Gracilinanus is described on the basis of a specimen found in a museum collection. The new species is known only from the type locality, which is located in the Yungas phytogeographic province near the Parque Nacional Calilegua, Jujuy Province, Argentina. Presently, the area is highly disturbed because of agricultural activity, mainly the cultivation of sugar cane. External, dental, and cranial morphology are described, and morphometric data as well as comparisons with other species in the genus Gracilinanus are presented.

We describe a new species of Thomasomys from the Vilcabamba Cordillera, Cuzco, Peru. This thomasomyine is a medium-sized, small-eared, and long-tailed rodent similar in external and cranial features to Thomasomys silvestris, a species from the western Andean slopes of Ecuador. The new species presents a unique combination of characters that includes the absence of genal vibrissae, absence of a “gap” between the hypothenar and thenar pads, short incisive foramina, and a primitive pattern of carotid circulation. The proposed new species is known only from the type locality, suggesting that its restricted distribution could be attributed to the existence of a relict fauna in the area.

This paper describes a stable chromosomal polymorphism in a species of tuco-tuco (Ctenomys minutus) and examines the dynamics of a narrow hybrid zone between chromosomal races distributed parapatrically on the coastal plain of southeastern Brazil. A cytogenetic survey studied 132 specimens of C. minutus from 22 trapping sites within the contact zone and surrounding areas. Seven polymorphic sites were identified; at all other sites, 2n was fixed for 2n = 46 or 48. A single chromosomal rearrangement is involved in the observed variation, which served as a diallelic Mendelian character in a Hardy–Weinberg analysis. Pooling polymorphic populations revealed that the mating system is random among genotypes (i.e., no mating bias is present or there is no purifying selection). Observed frequency of the metacentric chromosome follows a clinal variation. The hybrid zone is located along an ecotone, which could imply that exogenous selection is important in its maintenance. However, applying static-cline methodologies revealed weak exogenous selection, and it is possible that the hybrid zone could be the result of a relatively recent secondary contact with a width determined primarily by neutral diffusion. A historical scenario for the time, place or origin, and spread of the species and its chromosomal races is also presented.

Sequence variations in the mitochondrial cytochrome-b (Cytb) gene and the sex-determining gene of Y chromosome (Sry), which show maternal and paternal inheritance, respectively, were examined in 2 species of Japanese voles of the genus Eothenomys (Arvicolinae), E. andersoni and E. smithii, to elucidate phylogenies within and between species. Considerable intraspecific variation in Cytb was observed in both species, with clear geographic affinities, northeastern and central Honshu, Kii Peninsula of Honshu, Shikoku, and Kyushu (Japan), suggesting fairly ancient colonization in geographic areas. Genealogy of Cytb, however, was complicated and clearly discordant with current taxonomy. For example, the Kii Peninsula population of E. andersoni and the Shikoku population of E. smithii had unique haplotypes that differed from those of the remaining populations of both species. Sry gene variation, in contrast, was species specific and was polymorphic in E. andersoni with substantial geographic distribution, but it was monomorphic in E. smithii, suggesting a recent geographic expansion of E. smithii eastward. We attribute the complicated population genetics to topographic complexity of the Japanese islands and suggest that rearrangement of species was associated with climatic changes during the Quaternary glaciation on the basis of an assumption of divergence time among several murine rodents.

Neotoma fuscipes, the dusky-footed wood rat, is a morphologically diverse taxon with recognized intraspecific subdivisions that are based on both quantitative and qualitative morphology. Although there is substantial morphological variation within this taxon, intergradation among the various forms has been observed by previous workers. A recent survey of mitochondrial DNA revealed a high degree of molecular divergence within the taxon. Here, morphological, mitochondrial sequence, and nuclear microsatellite data are examined in a contact zone between 2 reciprocally monophyletic mitochondrial clades. On the basis of concordance of qualitative cranial, glans penes, and molecular characters, the 2 units appear to be genetically isolated from one another, leading to the elevation of N. macrotis to a species separate from N. fuscipes.

Multiple paternity in single litters (siring of offspring by >1 male) has been documented in several taxa with different mating systems. However, information on occurrence of multiple paternity in ungulates is lacking. We used 19 DNA microsatellite markers to assign parentage in 41 litters of captive white-tailed deer (Odocoileus virginianus) born in 6 pens with multiple males during 1997–1999. We detected multiple paternity in 7 of 27 litters with ≥2 offspring, occurring in 4 of 6 pens: 2 of 3 triplet litters and 5 of 24 twin litters. This is the first reported evidence of multiple paternity for single ungulate litters, which indicates that some aspects of ungulate reproductive ecology are not well understood. The occurrence of multiple paternity in litters of free-ranging ungulates would have implications for ungulate mating systems and reproductive strategies. Sex-linked microsatellite markers may provide a promising method for investigating female promiscuity in free-ranging ungulate populations where litter size is typically ≤2 offspring.

All existing sea otter (Enhydra lutris) populations have suffered at least 1, and in some cases 2, population bottlenecks. The 1st occurred during the 18th and 19th centuries as a result of commercial hunting that eliminated sea otters from much their native range and reduced surviving populations to small remnants. The 2nd bottleneck occurred when small numbers of otters were reintroduced, via translocation, to areas where the species had been eliminated. We examined genetic variation at 7 microsatellite loci and the mitochondrial DNA (mtDNA) control region in 3 remnant populations, Amchitka Island (Aleutian Islands, Alaska), central coastal California, and Prince William Sound (Alaska), and in 2 reintroduced populations, southeast Alaska and Washington, that were founded with transplants from Amchitka, and in the case of southeast Alaska, individuals from Prince William Sound as well. We found no evidence of reduced genetic diversity in translocated populations. Average expected microsatellite heterozygosities (H_E) were similar in all populations (range, 0.40–0.47), and mtDNA haplotype diversities were higher in reintroduced populations (0.51 for both Washington and southeast Alaska) than in remnant populations (X̄ = 0.35; range, 0.18–0.45). The levels of genetic diversity we observed within sea otter populations were relatively low when compared with other mammals and are thought to be the result of fur trade exploitation.

The pine marten, Martes martes, and the beech marten, Ma. foina, are sympatric species that are often mistaken for one another and yet have different conservation and management priorities. Three microsatellites originally isolated from the Eurasian badger, Meles meles, were amplified and sequenced in Ma. martes and Ma. foina. One of the regions includes a dinucleotide repeat, which is long, imperfect, and variable in both Me. meles and Ma. martes but shorter, perfect, and fixed in size in Ma. foina. Probabilities of allele exclusion confirmed that products amplified from these microsatellites could be used as a simple species-specific marker to distinguish the 2 species of Martes.