We examined the systematics of round-eared bats (Tonatia and Lophostoma) using sequence data from the nuclear recombination activator gene-2 (Rag2) gene and the mitochondrial valine transfer RNA, 12S ribosomal RNA (rRNA), and 16S rRNA. Some analyses of the mitochondrial and combined data sets indicate that round-eared bats may be paraphyletic relative to the genera Phyllostomus, Phylloderma, and Mimon. Both nuclear and mitochondrial data sets indicate substantial genetic divergence between Tonatia and Lophostoma, and neither data set unambiguously demonstrates monophyly of round-eared bats. However, our analyses cannot exclude the possibility that round-eared bats form a monophyletic lineage that separated anciently into Tonatia and Lophostoma. Within the Tonatia lineage, T. bidens and T. saurophila are sister taxa but are divergent for both nuclear and mitochondrial sequences. Nuclear data suggest that L. silvicolum may be paraphyletic, as currently recognized, because L. evotis appears within this clade.

Relationships of 5 families within traditional Yangochiroptera (Furipteridae, Mystacinidae, Myzopodidae, Natalidae, and Thyropteridae) have been debated considerably for more than a century, resulting in several alternative hypotheses for their evolution and zoogeography. A recent cladistic assessment of diverse morphologic traits and another of mitochondrial deoxyribonucleic acid (mtDNA) sequences have contradicted both traditional classification of yangochiropterans and each other. Our goals were to test alternative phylogenetic hypotheses by examining DNA sequences (1.4 kb) from a nuclear gene (recombination-activating gene-2; Rag2) and, if appropriate, to examine family-level relationships based on concatenation of Rag2 and mtDNA sequences (4.1 kb). Relationships suggested by parsimony and Bayesian analysis of Rag2 data were congruent with mtDNA, and combined analysis afforded high statistical support for all but 2 clades. These molecular data strongly support Noctilionoidea (Furipteridae, Mormoopidae, Mystacinidae, Noctilionidae, Phyllostomidae, and Thyropteridae) and Vespertilionoidea (Molossidae, Natalidae, and Vespertilionidae) and strongly contradict traditional association between Myzopodidae and other noctilionoid or vespertilionoid families. This study, current distributions, and limited fossil record strengthen the hypothesis of a New World origin for Noctilionoidea and suggest an Old World origin for Myzopodidae. Despite considerable statistical support afforded by these molecular data, further study using extensive taxonomic sampling of all bat families is needed to fully resolve relationships among Myzopodidae, Noctilionoidea, and Vespertilionoidea.

The murine mouse opossum Marmosa murina is a widely distributed species in tropical South America. In northeastern South America, authors propose the recognition of several subspecies, of which 2 might be found in French Guiana: a paler taxon (M. murina murina) inhabiting the narrow coastal strip and a darker one (M. m. muscula) occurring in the inner rainforests. We present here results of molecular analyses for 2 mitochondrial fragments (cytochrome-b gene and control region) and morphological examination of 3 external and 15 cranial measurements. These data support the presence of only 1 subspecies (M. m. murina) in French Guiana based on the absence of genetic structure and morphological divergence. Nevertheless, it appears that M. murina shows substantial morphometric variation across the Guianan shield with respect to the dental measurement M1–M4. This suggests that M. murina could be a differentiated taxon in the Guianas, likely comprising more than one biological entity.

The Colombian small-eared shrew, Cryptotis colombiana Woodman and Timm, was described from the Colombian Andes in 1993. Its original allocation to the C. nigrescens group recently was questioned based on several cranial characters the species appeared to share with some members of the C. thomasi group. We review characteristics of the C. nigrescens and C. thomasi groups, and we describe the humerus of C. colombiana and the humerus and manus of C. medellinia. The morphology of the humerus joins the suite of characters that supports the hypotheses that C. colombiana is not a member of the C. thomasi group and that all remaining South American species form a cohesive, definable set that is probably monophyletic.

Information regarding morphology of wild cheetahs is scant, and even where data exist they rarely were collected using a standardized methodology. We used a consistent technique to examine 241 wild Namibian cheetahs (Acinonyx jubatus jubatus) to study morphology, sexual dimorphism, growth rates, and physical condition and to investigate how these data compared with those in previous studies. Significant sexual dimorphism was evident for all measurements. The majority of cheetahs were in excellent condition at the time of examination, although old cheetahs and those that had been held captive for more than a month were in significantly poorer condition. Both male and female cheetahs reached adult body mass at 49–96 months of age. These data differed significantly from those collected during other studies, although such differences may be due to variations in collection methodology. It is therefore vital to standardize morphometric data collection techniques so that the true extent of differences between populations can be assessed more accurately. A suggested standardized collection methodology is presented.

The sibling multimammate mice, Mastomys natalensis and M. coucha, occur throughout southern Africa, exhibiting limited sympatry. We examine body mass and growth characteristics of both species, from birth to 26 weeks of age. Gompertz growth curves were fitted to data for body mass and lengths of head and body, tail, hind foot, and ear. Males of both species exhibited greater asymptotic values, faster maximum growth rates, later age of maximum growth, and extended growth periods than females. However, neither species established body mass dimorphism before weaning, suggesting that differential maternal investment between sexes is not important in preweaning growth. Furthermore, M. natalensis exhibited significantly faster maximum growth rates to reach a greater predicted asymptotic mass than M. coucha. We discuss these results in relation to mating system and interspecific competition.

The fundamentals of mechanics provide a strong basis for the hypothesis that allometry could be an important constraint on evolutionary changes in shape. Empirical evidence that allometry accounts for sufficient shape variation to be an effective constraint is much weaker. Numerous studies claim to show that most shape variation is correlated with size, but nearly all these studies use morphometric methods that confound size and shape. Consequently, the proportion of the shape variation correlated with size remains unknown. To address this issue, I examined ontogenetic change and adult variation in lower jaws of the fox squirrel, Sciurus niger. Jaw morphologies were quantified using traditional distance measurements and geometric shape variables computed from landmark coordinates. The same analyses were performed on each data set. As expected, analyses of the distance measurements found that allometry accounted for nearly all ontogenetic variation. The same analysis on the coordinate data found that allometry accounts for <50% of the ontogenetic variation in shape. In analyses of adults, allometry explained >50% of the variation in distance measurements but <25% of the variation in shape. These results confirm that analyses of distance measurements confound size and shape and that this can lead to erroneous claims about the importance of allometry.

Sperm quantity and quality were examined in 2 populations (from Mar de Cobo and Necochea, Argentina) of the subterranean rodent Ctenomys talarum (tuco-tuco) for which polygyny was confirmed as their mating system. Nonetheless, differential population attributes allow us to propose that polygyny may be exerted at different levels. Mean epididymal sperm counts were not different, but the Necochea population was characterized by higher variance in sperm counts. Low sperm production, with little variance, in the Mar de Cobo population is consistent with a more extreme polygyny, with aggression playing an important role in the males securing monopolization of females. In the Necochea population, where males were less likely to maintain female exclusivity, subordinant males are not driven away and may invest more in sperm production than in male–male interactions. However, C. talarum males from both populations produce high-quality sperm cells, based on their motility, percentage of live sperm cells, and morphology.

Glossophagine bats (Phyllostomidae, Glossophaginae) are specialized visitors to the flowers of several hundred species of neotropical plants. They are able to exploit flowers in hovering flight by imbibing nectar with a highly protrusile brush-tip tongue. As tongue extension is achieved by muscular and vasohydraulic mechanisms, its operational length can be inferred only from actively feeding animals. For this study, we measured maximum tongue extensions during nectar feeding in 9 species of glossophagine bats. We trained bats to feed from vertically oriented glass test tubes (9- and 15-mm inside diameter). The maximum depth of nectar drainage by a bat was recorded as maximum operational tongue length. Measured operational tongue lengths were in the range of the total body length of bats. The record length was 77 mm (in tubes with 15-mm inside diameter) in the 17-g flower specialist Choeronycteris mexicana. This compares with only 11–24 mm in the nonglossophagine frugivorous bat Carollia perspicillata, an opportunistic nectar feeder. The capacity for tongue extension proves the specialized status of neotropical glossophagines as flower visitors and clearly distinguishes them anatomically and ecologically from nonglossophagine nectar-feeding bats.

Rumination-like behavior, or merycism, of 5 adult male koalas (Phascolarctos cinereus) with various degrees of tooth wear was investigated using acoustically sensitive radio telemetry. Increased tooth wear was associated with a significant increase in mean rate of merycism mastication, mean number of merycism mastications per bout per 24 h, and mean number of mastications per 24 h. The ratio of mean number of ingestive mastications to mean number of merycism mastications per 24 h remained approximately 17:1 with increasing tooth wear. These results suggest that in contrast to true rumination, alterations in merycism behavior may be important in compensating for reduced molar effectiveness.

We provided 2 social groups of yellow-bellied marmots (Marmota flaviventris) with 2 types of supplemental feed (high and low protein) to test hypotheses about effects of food abundance and quality on juvenile growth rates and survival. Both supplemented litters and reference litters ceased to gain body mass by 2 weeks before hibernation even though supplemented litters had access to supplemental food. Body mass at weaning did not differ significantly between the 2 groups, but supplemented young had significantly higher growth rates (21.4–48.7 g/day) than reference young (24.1–33.3 g/day) and therefore had higher body mass late in the season. Juveniles that received high-protein supplements grew faster than the low-protein group. The addition of high-protein feed did not increase survival; however, juveniles that received low-protein feed were more likely to survive. Juveniles with higher body mass were not more likely to survive. Marmots must reach a critical body mass to survive hibernation and do not appear to benefit from mass gain beyond the critical body mass.

Muskoxen (Ovibos moschatus) are sexually dimorphic ruminants from a highly seasonal environment. Five males and 4 females were assigned at the start of spring (309 days) to supplemental diets of either 12.8% or 25.1% protein with ad libitum grass hay (9.1% protein). Males grew more rapidly than females especially in the 2nd autumn (0.29 versus 0.15 kg/day) but returned to slow growth in the next winter (0.09 kg/day). Water space (³H₂O) grew from 62 to 94 kg, whereas fat increased from 1.36% to 16.52% of body mass from 312 to 522 days of age. Depth of subcutaneous fat was greater on the high nitrogen (N) supplement, which indicated deposition of excess dietary protein as lipid. Differences in protein content and ¹⁵N enrichment of the supplements did not affect density, composition, or enrichment of hair, which indicated minimal incorporation of supplemental protein into lean mass and a low requirement of N for growth. Low body fat may impair survival of muskoxen during the 1st winter, whereas gains of mass as fat and lean tissue in the 2nd summer may be influenced by diversity and abundance of forage and by differential maturation of males and females.

Many female bats give birth to a single large young that is weaned at about 90–95% adult size and about 70–80% adult postpartum mass. The need for young to become independent fliers as quickly as possible presumably drives this burdensome development. We considered whether minerals or nitrogen in milk could limit reproductive and developmental capacity in bats. Milk samples were collected during the course of lactation from captive Artibeus jamaicensis and Phyllostomus discolor with known-aged young. Milk mineral (calcium, magnesium, sodium, potassium, and iron) and nitrogen concentrations did not significantly change during the course of lactation, except for sodium, which decreased in A. jamaicensis. When compared with other bats, concentrations of minerals and nitrogen in milk were weakly associated with phylogeny. We calculated daily accretion rates and total amounts of minerals and nitrogen in the body of young bats for each day of development. We also present calculations of the mass of milk required each day to meet accretion of minerals and nitrogen throughout the course of postnatal growth. From these analyses, we found that, except for calcium, minerals and nitrogen in milk were present in concentrations that exceeded the needs of developing young.

We tested the hypothesis that induced ovulation is adaptive in North American carnivores by providing a mechanism to overcome the risk of unsuccessful mating in solitary species living in seasonal environments and a method for females to evaluate male quality via sexual selection inside the reproductive tract. We obtained published data on North American carnivores and determined from their distribution a coefficient of seasonality and primary productivity. Using traditional statistics and comparative methods, we determined that induced ovulators lived in more seasonal environments apparently not influenced by energy. No statistical differences in behavioral traits existed between induced and noninduced ovulators, but trends in data were consistent with our predictions, with induced ovulators tending to have larger home ranges and longer estrous periods. Mating systems also differed between the groups: induced ovulators were characterized by mostly (93%) multimale mating systems, whereas noninduced ovulators were monogamous (42%), multimale (33%), or polygynous (25%). Also, induced ovulators exhibited larger sexual dimorphism and smaller neonates than noninduced ovulators or felids. We suggest that induced ovulation evolved through sexual selection as a reproductive strategy beneficial for males (assurance of egg fertilization during short pair bonds) and females (postcopulatory mate choice based on level of stimulation causing induced ovulation).

We examined reproductive seasonality in 2 populations of the harbor porpoise (Phocoena phocoena) in the eastern and western North Atlantic Ocean and compared our observations with historical data from the Baltic and North seas. Dates of conception for individuals were back-calculated from fetal size and an estimated fetal growth rate of 83 mm/month. Mean conception date was 6 July ± 9.5 days (SD) in the Bay of Fundy and Gulf of Maine and 25 July ± 20.3 days in the Kattegat and Skagerrak seas. Timing of conception did not differ between the Kattegat and Skagerrak and the North seas but was significantly earlier there than in the Baltic Sea (18 August ± 11.8 days). Based on mean body size at birth (a mass of 6,025 ± 440 g and a length of 762 ± 54 mm), gestation was estimated to last for approximately 10.4 months. We hypothesize that differences in mating seasons reflect seasonal patterns in distribution and behavior of prey, so calves are born when maternal prey is abundant and is of high quality.

We investigated scale-dependent habitat selection by the southern red-backed vole (Clethrionomys gapperi) in subalpine forests and 20- to 30-year-old regenerating timber harvests of the central Rocky Mountains. At the macrohabitat level, C. gapperi preferred forest stands, which had more overstory canopy cover, more uniformly distributed coarse woody debris (CWD), and more dwarf huckleberry (Vaccinium scoparium) than regenerating harvested stands. Further, C. gapperi was captured in forest stands up to harvest boundaries but crossed them significantly less than expected by chance. Analysis of microhabitat selection indicated that, in forest stands, C. gapperi showed selection at a fine spatial scale, strongly favoring CWD microhabitats and avoiding those dominated by V. scoparium. Our results suggest that older, regenerating clear-cuts in the Rocky Mountains can have clearly defined impacts on C. gapperi similar to those immediately after timber harvests, but that regenerating clear-cuts do support some use by C. gapperi. The results support the association of C. gapperi with CWD and forest overstory in western montane habitats and indicate a noticeable response to forest boundaries but no direct edge effect.

Many biological theories have been proposed to explain latitudinal and elevational gradients of species richness, but only recently have theories been proposed that suggest that these patterns may be due solely to geographic constraints. These null models predict mid-domain peaks in species richness as a consequence of geometric patterns resulting from overlapping species ranges between 2 geographic boundaries. Desert rodents exhibit a marked mid-domain peak in species richness for boundaries defined by the latitudinal extent of North American deserts (19°N–45°N). Empirical patterns are compared with predictions of 2 null models: an analytical–stochastic model and the binomial model. Empirical species richness occurs almost entirely within 95% prediction curves of the analytical–stochastic model. Observed species richness is highly correlated with predictions of the binomial model (r² = 93%) but does not generally occur within 95% confidence intervals, in part because empirical range-size distributions differ from predicted distributions. Other diversity theories, species–area relationships, productivity gradients, latitudinal gradients, and Rapoport’s rule are evaluated; none is consistent with empirical patterns. These results demonstrate that the mid-domain effect is a consequence of overlap of variably sized ranges within a bounded region for both ecologically defined hard boundaries and boundaries determined by the shape of the earth. The significant deviations from null-model predictions become the biological points of interest: skewed or localized (or both) pulses or depressions of species richness. Deviations in the present analysis demonstrated a localized pulse in richness caused by a local hard boundary, the Baja peninsula.

Niches of 2 cervids (chital, Axis axis and sambar, Cervus unicolor) and 2 bovids (nilgai, Boselaphus tragocamelus and chinkara, Gazella bennetti) from semiarid forests in western India were studied for habitat use and food habits. Habitat use was analyzed by discriminant analysis using 20 variables, and food habits investigated by analyzing undigested plant remains in pellets. Cervids and bovids differentiated primarily according to vegetation and terrain features, and the 2 deer species showed separation in diet. The 2 cervids selected forested areas, whereas the 2 bovids selected scrubland and were more tolerant of disturbances like livestock grazing and also showed a high similarity in food habits. Habitat use and food habits were analyzed with nonmetric multidimensional scaling to assess their combined effects. A greater degree of similarity in resource use between the 2 bovids suggests that they may be competitive, at least during periods of forage scarcity.

Habitat loss might be one of the primary reasons for the decline of the swift fox (Vulpes velox) in the western Great Plains of North America. From 1998 to 2001, we monitored 42 swift foxes in a landscape interspersed with native short-grass prairies, nonnative grasslands enrolled in the Conservation Reserve Program, irrigated agricultural fields, and dry-land agricultural fields. Survival estimates ranged from 0.52 to 0.66 for both adults and juveniles, and the primary causes of death were vehicle collisions (42% deaths) and coyote (Canis latrans) predation (33%). Annual home-range size was similar for males and females (10.8 and 10.5 km², respectively). Within the study area, swift foxes selected only short-grass prairies and had lower-than-expected use or complete avoidance of all other habitat types. Our results indicate swift foxes are more specialized in habitat selection than other North American canids; thus, protection of native short-grass prairies might be necessary for their long-term existence.

We studied demographics of a population of gray foxes (Urocyon cinereoargenteus) that has been protected for over 50 years on the United States Department of Energy’s Savannah River Site, near Aiken, South Carolina. The percentages of individuals in the 10-, 22-, and ≥34-month-old age classes were 37.2, 10.3, and 52.6, respectively. This differed significantly from age structure at this same site in 1954–1956. Sex ratio was biased toward females (58.7%). Average litter size was 3.6 ± 0.2 SE, and the barren rate was 11.1%. The greater proportion of females, however, resulted in an overall per capita reproductive rate that was still comparable with populations subject to harvest pressure.

Large carnivores range more widely than many other terrestrial mammals, and this behavior tends to bring them into frequent conflict with humans. Within any carnivore population, individual variation in patterns of space use should be expected to make some animals more vulnerable than others to risks of mortality from humans and other sources. In this study, our goal was to document variation among individuals in space use by female spotted hyenas (Crocuta crocuta). We examined predictions of hypotheses suggesting that space use by female hyenas is affected by reproductive state, social rank, and local prey abundance. Home-range size, distance at which females were found from the current communal den, and distance at which they were found from the nearest territorial boundary all varied significantly with the 3 independent variables. Females with den-dwelling cubs had smaller home ranges, were found closer to the communal den, and were found farther from the territorial boundary than were females with no den-dwelling cubs. Neither social rank nor prey availability significantly influenced the space-use patterns of females with den-dwelling cubs. Among females with no den-dwelling cubs, high-ranking females had smaller home ranges, were closer to the communal den, and were farther from the territorial boundary than were low-ranking females. The females ranging most widely were low-ranking individuals with no den-dwelling cubs when they were observed during periods of prey scarcity.

We used observations of known-age, free-ranging spotted hyenas (Crocuta crocuta) from a large social group to develop age-estimation models. A model based on tooth-eruption data estimates the ages of animals 10.0–15.5 (±1.1 SD) months old. We used tooth-wear data to estimate the ages of adult males ±4.9 months and ages of females ±22.6 months. Analysis of known and estimated ages shows that males usually disperse from their natal group when 24–60 months of age. Eight of 20 males whose fates were known lived in 3 groups over time, and at least 7 of 41 resident immigrant males appeared to arrive in the study group years after leaving their birthplaces. Thus, males of this species often engage in multiple dispersal events.

Numbers of banner-tailed kangaroo rats, Dipodomys spectabilis, have declined sharply in some but not all populations monitored in southeastern Arizona over the past 20 years. We describe concurrent changes in vegetation and report the results of microhabitat manipulation experiments in which we removed broom snakeweed, Gutierrezia sarothrae, from 1.00-ha (pilot) or 0.56-ha (replicate follow-up) plots. D. spectabilis became extinct on control plots, but populations remained stable on plots where snakeweed was removed. On a larger scale, declines in numbers of kangaroo rats coincided with increases in density of woody plants. The data substantiate the preferences of this species for structurally open microhabitats and document that survival rates are higher in areas that are more open. Large kangaroo rat species like D. spectabilis are often regarded as keystone species, and our results indicate that they are vulnerable to grassland degradation.

We studied the Prince of Wales flying squirrel (Glaucomys sabrinus griseifrons) in temperate rain forest of southeastern Alaska to provide the 1st quantitative estimates of demography from southeastern Alaska and test predictions of the hypothesis that Sitka spruce (Picea sitchensis)–western hemlock (Tsuga heterophylla) forest is primary habitat for G. sabrinus in southeastern Alaska. We expected that abundance, body condition, productivity, and summer and overwinter survival of G. sabrinus would be higher in spruce–hemlock forest (which typically are the old-growth forests of upland sites [upland-OG]) than in peatland-scrub–mixed-conifer (peatland-MC) forest. Mean values of minimum number of animals known alive and density during autumn were higher in upland-OG than in peatland-MC, and both were about 2 times higher than corresponding spring values. Age and sex composition of the population was similar among years, between seasons, and between habitats. Males comprised a larger portion of the population in upland-OG than in peatland-MC forest. Mean body mass was similar between habitats. Minimum summer survival varied among years and between habitats. Overwinter survival was less varied and similar among years and between habitats. Reproductive females were more abundant in upland-OG than in peatland-MC, but percentage of reproductive females during spring and percentage of juveniles during autumn were similar between habitats. These results support the conclusion that upland-OG forests of southeastern Alaska are primary habitat for northern flying squirrels. Still, squirrel densities in peatland-MC were higher than those reported for several managed and unmanaged forest types in the Pacific Northwest, and some demographic parameters were similar between upland-OG and peatland-MC. In southeastern Alaska, peatland-MC habitat likely contributes to breeding populations of G. sabrinus and reduces risk of viability in managed landscapes.

Common brushtail possums (Trichosurus vulpecula) are environmental and agricultural pests in New Zealand. This article investigates their denning behavior and the response of such behavior to density reduction. Brushtail possums prefer to den in trees with large diameters. Individuals in the populations recovering from density reduction used more den sites than those in preremoval populations. Simultaneous den sharing was uncommon in both preremoval and recovering populations. Sequential den sharing was common and occurred mostly between females and males. Den-sharing frequencies were not reduced by population reduction. Our results indicate that transmission of diseases between brushtail possums through den sharing is not likely to be greatly affected by density reduction.

We studied roosting ecology of reproductive (pregnant or lactating) adult female eastern pipistrelles (Pipistrellus subflavus) in Indiana. Nineteen bats were radiotagged and 37 roost trees identified. Pipistrelles roosted exclusively in foliage, typically in clusters of dead leaves (65%) and less often in live foliage (30%) or squirrel nests (5%). Oaks (Quercus species) were preferred as roost trees. Roost trees and height of foliage roosts were both located well below the forest canopy. Bats remained at roost trees for 6 days on average before moving to new roosts and traveled approximately 19–139 m between roost trees. This is the 1st thorough analysis of roosting habits of this common species under natural conditions.

We examined movements and habitat use by female Rocky Mountain elk (Cervus elaphus) and mule deer (Odocoileus hemionus) using a large telemetry data set collected over 6 years at the Starkey Experimental Forest and Range in northeastern Oregon. The analysis contrasted hourly movements of elk and deer within the mosaic of vegetation and landforms at Starkey with daily and seasonal demands for forage, security, and other resources. Telemetry data from 15 April to 14 November, 1991–1996, were stratified into 30-day intervals and tested for daily cycles relative to habitat use and movements. Both elk and deer exhibited strong daily and seasonal patterns of movements and habitat use. Daily cycles were most pronounced during spring and autumn, were composed of crepuscular and intraday habitat transitions, and were more pronounced for elk than for deer. Although crepuscular transitions were accompanied by sharp increases in velocity, intraday changes in habitat were not. The results add considerable detail to previous studies that sampled only limited hours of the day and seasons of the year. The findings have significance for modeling efforts that attempt to replicate animal behavior on diverse landscapes.

Olfaction is important in mammals and other animals for foraging, predator avoidance, and communication. However, very little is known about how the physical environment influences the activity of odorants. Many pesticides are organic molecules that appear to behave similarly to odorants of interest to rodent foragers. In this article, the literature on pesticide residues is used to construct a conceptual model of how odorants might behave under different environmental conditions. The primary focus of the model concerns how the environment might affect detection of buried seeds by rodents. The most important environmental variable influencing volatilizing of pesticides from soil is water content of soil. In dry soil, pesticides are adsorbed onto soil particles. However, when soil moisture increases above a monomolecular layer, pesticides desorb and vapor densities increase dramatically. These observations on changes in vapor density of pesticides as soil moisture changes are consistent with experimental data on olfaction in rodents. Other factors that influence pesticide volatilization include relative humidity, temperature, wind, soil characteristics (particle size, organic matter, and bulk density), and burial depth. Limited data suggest that these factors also influence the vapor density of odorants and, therefore, olfaction. The literature on pesticides allows us to make predictions about how animals detect odorants and then test those predictions experimentally.

Predation and food are dominant forces regulating snowshoe hare (Lepus americanus) population density, yet manipulations of these factors have not proven sufficient to explain all aspects of hare population dynamics. Social interactions among hares have often been dismissed as unimportant in population regulation, but the mechanisms and consequences of such interactions have not been well studied. In this study, we examined one aspect of social behavior in snowshoe hares that has been hypothesized to be important in the spacing behavior of other species of small mammals: interactions among related individuals. We sampled 68 hares on two 7.3-ha grids in the southwest Yukon Territory during a cyclic peak phase of population density and used livetrapping and radiotelemetry to quantify spacing behavior. Hares were genotyped at 7 microsatellite DNA loci, and relatedness (r) among individuals was estimated and correlated with spacing. Average relatedness was low on both grids (≤0) because very few close kin were present. Hares were not more or less likely to associate with kin than they were with nonkin. The results were similar when males, females, adults, and juveniles were considered together or separately and are thus consistent with a lack of sex-biased dispersal in snowshoe hares. Kin are not clustered in snowshoe hare populations, thus interactions among kin do not likely have a strong influence on hare spacing behavior. This study supports the idea that spacing behavior has little influence on hare population dynamics, at least during the peak phase of the cycle.

This study examined spatial-learning ability of the least shrew, Cryptotis parva, in a complex maze and the effects of senescence on spatial learning and maximal running speeds. This represents the 1st such study on these parameters for soricids. Shrews from 3 age groups, juvenile (20–23 days old), young but sexually mature (50–54 days), and senescent (20 months), were tested in a maze containing 5 blind alleys. The number of blind-alley errors was recorded during a 10-day training period. On the 1st day of training, there was a significant difference in performance between senescent (123.4 errors ± 14.1 SE) and young (68.9 ± 5.8 errors) shrews and between senescent and juvenile shrews (74.3 ± 7.2 errors). During the 10-day period, there was a significant decrease in mean number of errors: from 74.3 to 3.3 for juvenile shrews, 68.9 to 2.4 for young shrews, and 123.4 to 16.6 for senescent shrews. There was no significant difference in decrease in errors between juvenile and young shrews. Young shrews had significantly higher maximal running speeds (15.3 km/h ± 3.2 SE) in a racetrack as compared with senescent shrews (8.8 ± 2.7 km/h). These results demonstrate for the 1st time that aging impairs running speed and spatial-learning ability in C. parva and that these 2 parameters may be related.