“… discovered a Village of Small animals that burrow in the grown (those animals are Called by the french Petite Chien) … we found 2 frogs in the hole and Killed a Dark rattle Snake near with a Ground rat [prairie dog] in him … Those Animals are about the Size of a Small Squ[ir]el … much resembling a Squirel in every respect … his tail like a ground squirel which they shake and whistle when allarmd … it is Said that a kind of Lizard also a Snake reside with those animals.” (Meriwether Lewis, Lewis and Clark Expedition, 17 September 1804)

Of the 3 major factors (habitat loss, poisoning, and disease) that limit abundance of prairie dogs today, sylvatic plague caused by Yersinia pestis is the 1 factor that is beyond human control. Plague epizootics frequently kill >99% of prairie dogs in infected colonies. Although epizootics of sylvatic plague occur throughout most of the range of prairie dogs in the United States and are well described, long-term maintenance of plague in enzootic rodent species is not well documented or understood. We review dynamics of plague in white-tailed (Cynomys leucurus), Gunnison's (C. gunnisoni), and black-tailed (C. ludovicianus) prairie dogs, and their rodent and flea associates. We use epidemiologic concepts to support an enzootic hypothesis in which the disease is maintained in a dynamic state, which requires transmission of Y. pestis to be slower than recruitment of new susceptible mammal hosts. Major effects of plague are to reduce colony size of black-tailed prairie dogs and increase intercolony distances within colony complexes. In the presence of plague, black-tailed prairie dogs will probably survive in complexes of small colonies that are usually >3 km from their nearest neighbor colonies.

Intercontinental movements of invasive species continue to modify the world's ecosystems. The plague bacterium (Yersinia pestis) has colonized and altered animal communities worldwide but has received much more attention as a human pathogen. We reviewed studies on the ecology of Y. pestis in ancient foci of central Asia and in western North America, where the bacterium apparently has become established much more recently. Although rodent populations on both continents are affected dramatically by epizootics of plague, the epidemiologically important species of Asia demonstrate resistance in portions of their populations, whereas those of North America are highly susceptible. Individual variation in resistance, which is widespread in Asian rodents and allows a microevolutionary response, has been documented in few North American species of rodents. Plague increases costs of sociality and coloniality in susceptible hosts, increases benefits of disease resistance in general, and increases benefits of adaptability to variable environments for species at higher trophic levels. Prairie dogs (Cynomys) epitomize taxa with high risk to plague because prairie dogs have uniformly low resistance to plague and are highly social. Relationships to plague are poorly understood for many North American rodents, but more than one-half of the species of conservation concern occur within the geographic range of plague.

Long-term research with marked individuals shows that black-tailed, Gunnison's, and Utah prairie dogs (Sciuridae: Cynomys ludovicianus, C. gunnisoni, and C. parvidens) all reproduce slowly, despite claims of ranchers and early naturalists. Five factors are responsible for the slow reproduction. First, survivorship in the 1st year is <60% for all 3 species, and it remains low in later years. Second, even under optimal conditions, females of all 3 species produce only 1 litter/year. Third, the percentage of males that copulate as yearlings is only 6%, 24%, and 49% for black-tailed, Gunnison's, and Utah prairie dogs, respectively. The percentage of females that copulate as yearlings is only 35% for black-tailed prairie dogs, but it is 100% for both Gunnison's and Utah prairie dogs. Fourth, the probability of weaning a litter each year is only 43%, 82%, and 67% for female black-tailed, Gunnison's, and Utah prairie dogs, respectively. Fifth, for those females that wean offspring, mean litter size at 1st juvenile emergence from the nursery burrow is 3.08, 3.77, and 3.88 for black-tailed, Gunnison's, and Utah prairie dogs, respectively.

During 1997–1998, we undertook an aerial survey, with an aerial line-intercept technique, to estimate the extent of colonies of black-tailed prairie dogs (Cynomys ludovicianus) in the northern Great Plains states of Nebraska, North Dakota, South Dakota, and Wyoming. We stratified the survey based on knowledge of colony locations, computed 2 types of estimates for each stratum, and combined ratio estimates for high-density strata with average density estimates for low-density strata. Estimates of colony areas for black-tailed prairie dogs were derived from the average percentages of lines intercepting prairie dog colonies and ratio estimators. We selected the best estimator based on the correlation between length of transect line and length of intercepted colonies. Active colonies of black-tailed prairie dogs occupied 2,377.8 km² ± 186.4 SE, whereas inactive colonies occupied 560.4 ± 89.2 km². These data represent the 1st quantitative assessment of black-tailed prairie dog colonies in the northern Great Plains. The survey dispels popular notions that millions of hectares of colonies of black-tailed prairie dogs exist in the northern Great Plains and can form the basis for future survey efforts.

Despite the broad and relatively stable distribution of the black-tailed prairie dog (Cynomys ludovicianus) throughout much of the Pleistocene and Holocene, anthropogenic activities have reduced the current range of this native grassland species and its associated biotic community to <5% of its historic range (approximately 1800—Miller et al. 1990, 1994). We studied the biogeography of the black-tailed prairie dog along the southeastern edge of its geographic range with 3 primary objectives: to assess the status of the species in this region and identify trends in town coverage and mean town size over the past century, to test whether town persistence was associated with area and isolation of towns, and to assess the protection status of towns >10 ha by comparing locations of extant towns to those of protected public lands. Prairie dog towns in this region now represent only 1% of presettlement estimates and continue to decline in total acreage because of advanced agricultural practices, systematic control measures, and outbreaks of plague. Further, <1% of the area now occupied by prairie dog towns >10 ha occurs within protected locations. As the total coverage of towns has declined, mean size of towns has decreased, and towns have become increasingly more isolated. Persistence of towns between 1989 and 1997 was highest for the largest and most isolated towns, even in regions that were not known to be influenced by plague.

Habitat alteration, agricultural control, recreational shooting, and most recently, sylvatic plague (caused by Yersinia pestis) contributed to local extinctions and a steady decline of black-tailed prairie dog (Cynomys ludovicianus) throughout its range. As a consequence, prairie dogs currently live in metapopulations, where their overall persistence will depend on a balance between extinction of colonies and recolonization from extant colonies. Patterns of genetic similarity among colonies, as measured by neutral molecular markers, provide an estimate of the dispersal and gene flow among colonies within prairie dog metapopulations. We sampled 13 colonies of black-tailed prairie dogs in short-grass prairie of northern Colorado, 100-km east of Fort Collins, Colorado. We used historical records and genetic analysis to show that colonies undergo regular extinctions, which subsequently are recolonized by individuals from multiple source colonies. We examined 155 individuals for variation at 7 microsatellite loci and found moderate levels of genetic differentiation among colonies (Θ [=F_ST] = 0.118). We also used assignment and exclusion tests based on multilocus genotypes of individuals to determine the probability that individuals originated from the same colony in which they were captured. About 39% of individuals could not be assigned to colonies where they were captured, indicating they were either immigrants (adults) or the offspring of immigrants (adults and juveniles). We tested for genetic isolation by distance among colonies by comparing genetic distances to geographic distances between colonies. Akaike's Information Criterion for model selection revealed that dispersal most likely occurred along low-lying dry creek drainages connecting isolated colonies. Genetic distances between colonies were also related to ages of colonies; older colonies were more similar genetically than younger colonies. This underscores the importance of dispersal among prairie dog colonies and has important implications for persistence of prairie dog metapopulations, in which all colonies, regardless of size, are vulnerable to extinction from plague.

Levels of sequence variation in mitochondrial cytochrome-b gene were examined to ascertain if this molecule can provide a reference point in making decisions concerning species-level distinctions. DNA-sequence data from 4 genera of rodents (Neotoma, Reithrodontomys, Peromyscus, and Sigmodon) and 7 genera of bats (Artibeus, Carollia, Chiroderma, Dermanura, Glossophaga, Rhinophylla, and Uroderma), including recognized sister species, were examined to develop hypotheses for evaluating levels of sequence variation. Several patterns associated with DNA-sequence variation emerged from this study. Specifically, genetic distance values <2% were indicative of intraspecific variation; values between 2 and 11% had a high probability of being indicative of conspecific populations or valid species and merit additional study concerning specific status; and values >11% were indicative of specific recognition. It appears that genetic distance values may be useful for determination of species boundaries under the framework of the Genetic Species Concept.

Using a long-term data set (1989–1999), we examined how changes in abundance of 2 ecologically dominant species, prairie voles (Microtus ochrogaster) and hispid cotton rats (Sigmodon hispidus), affected the local diversity of a grassland rodent community at varying temporal scales. Species richness was associated positively with long-term fluctuations in the abundance of prairie voles and cotton rats over the 10-year period. Although increased vole densities consistently had a significantly negative effect on total community evenness, evenness of other community members was unaffected by fluctuating vole densities. Presence of cotton rats negatively affected both the relative abundance of other community members and the species richness during the years of high density (1991–1995), but did not exhibit longer-term influences. Thus, despite their numerical dominance, changes in prairie vole abundance had little ecological effect on the rest of the community, whereas the influence of cotton rats was density- and temporally dependent.

The prairie deer mouse (Peromyscus maniculatus bairdii) was more common than the white-footed mouse (P. leucopus) in museum collections from the 6 Illinois counties of the Chicago region before 1920 but constitutes only 5% of specimens deposited since 1970. Because white-footed mouse prefers woody vegetation and because prairie deer mouse is limited to prairie or large open habitats, the change in proportion is likely driven by a disproportionate loss of prairie among remaining natural habitat and increases in woody vegetation within grasslands. The decline of the prairie vole (Microtus ochrogaster) relative to the meadow vole (M. pennsylvanicus) and the lack of recent specimens of Franklin's ground squirrel (Spermophilus franklinii) corroborate the hypothesis that prairie habitats have declined much more so than wooded habitats in the Chicago region. Based on extinction models using museum records, it is probable that S. franklinii is already locally extirpated. Regression analysis suggests the white-footed mouse will be the only local Peromyscus in 0–140 years.

Baylisascaris procyonis is a parasitic nematode of raccoons (Procyon lotor) capable of infecting many species of small vertebrates as intermediate hosts. In these hosts, migrating larvae often cause fatal or severe central nervous system (CNS) disease. Previous research suggested that intermediate hosts become infected with B. procyonis while visiting raccoon latrines. We tested effects of ambient availability of food and duration of exposure on dynamics of transmission of B. procyonis to white-footed mice (Peromyscus leucopus) in a factorial design within enclosures containing artificially constructed raccoon latrines. Fifty percent of experimental mice acquired B. procyonis infections and 43% of infected mice developed CNS disease. Visitation to latrines was marginally greater (P = 0.095) for mice subjected to low availability of ambient food. The mean number of larvae per mouse was greater (P = 0.001) in low food group after exposures of 14–28 days. Probability of infection varied predictably as a function of duration of exposure (P = 0.005), and probability of CNS disease varied predictably as a function of level of ambient food available (P = 0.023). We conclude that transmission of B. procyonis occurs at raccoon latrines and that increased visitation to latrines and duration of residence in close proximity to a latrine, both increase probability of mortality due to CNS disease, especially when individuals are stressed by reduced resources or poor habitat.

We present the 1st detailed field study on the giant mole-rat (Cryptomys mechowi), a eusocial subterranean bathyergid rodent from mesic areas of subequatorial central Africa. In Copperbelt Province, Zambia, we found giant mole-rats in a variety of habitats including agricultural fields, bushland, marshes, and forests. Soil types varied in hardness and air content, and varied vertically and horizontally. Burrow systems of single colonies were 0.2–2.5 ha. The diameter of burrows was about 8 cm, and the maximum depth was about 200 cm. Nests were found at an average depth of 91 cm (n = 8). Further characteristics of nests, food and defecation chambers, diet, helminth parasites, and commensals are described. Colony size ranged from 3 to >20 with a sex ratio of 1:1.2 (n = 65) in favor of females, with 8% juveniles, 39% subadults, and 53% adults. A significant sexual dimorphism was found in the body mass (345 g ± 95 SD in males versus 252 ± 34 g in females). A defined breeding season was not apparent. Because C. mechowi occurs in a variety of habitats across a broad geographic range, generalizations based on the examination of selected study sites and consequent linking of behavioral ecology with habitat parameters should be done with caution.

The golden spiny mouse (Acomys russatus), an inhabitant of rocky deserts, exhibits adaptations to diurnal activity, but also some characteristics that appear evolutionarily constrained to a nocturnal mode of life. This species is probably driven into diurnality by its congener, the common spiny mouse (A. cahirinus). We carried out a comparative study of the retinal morphology of A. russatus and A. cahirinus, in search of possible anatomical adaptations for diurnal activity in the eyes of golden spiny mice. The observed photoreceptors of both species had rod-pattern properties that characterize nocturnal mammals. We also carried out a field study of the foraging microhabitat use of golden spiny mice and of illumination levels in those microhabitats. Throughout the year, golden spiny mice preferred to forage between and particularly under boulders, where light intensities were lower than in the open. Thus, the retinal structure of golden spiny mice has not evolved to meet with their needs as a diurnal species, but the combination of the biochemical properties of their eyes, coupled with their foraging microhabitat selection, may enable them to withstand diurnal activity with nocturnally adapted retinas.

There is a paucity of empirical data on gliding abilities of most gliding mammals, including flying squirrels in the genus Glaucomys. I assessed gliding performance of the northern flying squirrel (Glaucomys sabrinus) by calculating glide parameters for 100 glides observed between July 1999 and July 2000 in southern New Brunswick, Canada. G. sabrinus had a glide angle of 26.8° and a glide ratio of 1.98. The difference between the vertical drop at the start of a glide and the vertical rise at the end of a glide was about 1.91 m. Males tended to glide farther than females (X̄ = 19.0 m versus 14.2 m), although sexes did not differ in heights of launch (X̄ = 9.8 m) or landing (X̄ = 2.0 m). Red spruce (Picea rubens) trees were favored as landing sites over hardwood species. Most glides (59%) were with the slope of terrain, allowing a greater net height loss (X̄ = 10.2 m) than initial height of launch. Horizontal glide distance ranged from 3.2 to 45 m, with most glides being 5–25 m.

Many temperate rodents show a break in reproductive activity to conserve energy during harsh winter conditions. However, even in species that use photoperiodic changes to adjust reproductive functions, winter breeding has been recorded frequently and most likely is caused by different responses to changes in photoperiod. Furthermore, these reproductive phenotypes show clear physiologic and morphologic differences. We investigated winter reproduction in natural populations of 2 European rodents, the yellow-necked mouse (Apodemus flavicollis) and the bank vole (Clethrionomys glareolus). Analyses of our data indicate that winter breeding was due to nonresponsive phenotypes in both sexes. A broad range of gonadal changes was found, particularly in males, and individual differences in testis size were linked to differences in body weight. Population genetic analyses provided no hint of assortative mating between the 2 phenotypes.

Throughout the range of the Steller sea lion (Eumetopias jubatus), nearly all births of full-term pups observed from 1968 to 1998 occurred between 15 May and 15 July. We found significant differences in timing of births between rookeries with the earliest mean date of birth (4 June) at Forrester Island, Alaska, and the latest (21 June) at Año Nuevo Island, California. Mean date of birth becomes progressively later both north and south of Forrester Island. Births at individual rookeries were synchronous, with 90% of pups born within a 25-day period. We hypothesize that timing of births at rookeries is determined through selection for time periods when weather conditions are generally favorable for pup survival and when adequate prey items are predictably available near rookeries for lactating females. Temporal differences also were found in mean date of birth at 4 rookeries, with a maximum difference between earliest and latest mean date of birth of 10.2 days at Año Nuevo Island. The most likely explanation for temporal variability at individual rookeries is variable nutritional status of reproductive females.

Vocalizations of white-nosed coatis (Nasua narica) emitted in nonaggressive and aggressive contexts were measured and compared to determine if these calls exhibited acoustic characteristics in accordance with motivation-structural (MS) rules. “Chirp” and “squawk” calls were compared spectrographically using 11 coatis from 3 zoos. Chirps were short-duration (68.6–212.0 ms), high–maximum frequency (16.2–17.9 kHz), tonal calls with frequency modulations. Squawks were longer-duration (177.9–546.5 ms), low–maximum frequency (8.4–13.2 kHz), wide-bandwidth calls with 6 resonances and little frequency modulation. Squawks differed from chirps in duration, maximum frequency, and change in frequency (P < 0.001). Chirps were emitted during nonaggressive behaviors, whereas squawks were emitted during agonistic encounters. Squawks conformed to MS rule predictions for aggressive calls, and chirps supported MS rule predictions for nonaggressive contexts, but some exceptional characteristics were noted in chirps. Many chirps (67.7%) concluded with a short-duration, broad-bandwidth sound with high energy in low frequencies, and may represent variations of a graded call.

Many systematic relationships among Chinese white-toothed shrews of genus Crocidura are presently unresolved. In this paper, a taxonomic revision of Crocidura from Southern China is presented. We studied 338 specimens from Burma, China, Korea, Pakistan, Turkey, Middle and Central Asia, and Russia (^{Appendix I}), 285 of which had complete skulls that were analyzed with principal component and discriminant analyses. Results indicated that 6 species of Crocidura can be recognized in South China. C. fuliginosa occurs in Southwestern and Eastern China, C. attenuata is broadly distributed throughout Southern China, and C. horsfieldii is restricted to the southern part of China. C. vorax and C. rapax, usually placed as synonyms of the European C. russula, are recognized as 2 valid species whose ranges overlap in Southwestern China. C. shantungensis of Eastern Asia extends to the northern part of Southern China and is distinct from C. suaveolens and C. gmelini of Middle and Central Asia, respectively.

Karyotypes of 7 taxa of the rodent genus Oligoryzomys trapped in 33 localities from an area ranging from 01°N to 32°S in Brazil were analyzed. Three species were trapped exclusively in the Cerrado biome: O. stramineus, diploid number (2n) = 52, fundamental number (herein, number of autosomal arms; FN) = 68; O. eliurus, 2n = 62, with 2 fundamental numbers, FN = 64 and 66; and Oligoryzomys sp., 2n = 70, FN = 74. In the Amazon, we caught O. cf. messorius, 2n = 56, FN = 58, and O. microtis, 2n = 66, FN = 74. Oligoryzomys nigripes (2n = 61, 62, FN = 80–82) was trapped in 24 localities in various biomes, and O. flavescens from several sites in southern Brazil presented the same karyotypes as those already described at other sites. The C- and NOR-banding were performed for all species, and the (T₂AG₃)_n telomeric probe hybridized in situ to both the short and long arms of all pairs of karyotypes of O. cf. messorius, O. eliurus, and Oligoryzomys sp. An analysis performed with 11 microsatellite DNA heterologous primers improved differentiation of O. nigripes from O. eliurus individuals, 2 species that presented 2n = 62 and that were trapped at the same site.

Systematic relationships within the 5 recognized species of Glossophaga were assessed using the complete cytochrome-b gene (1,140 base pairs). Our samples from 4 species, G. commissarisi, G. leachi, G. longirostris, and G. morenoi, show little intraspecific geographic subdivision. Alternatively, G. soricina has a major mtDNA subdivision that may reflect 2 biological species. Our data suggest that G. soricina is the sister taxon to the remainder of the genus, G. leachi and G. longirostris are sister taxa, and the position of G. morenoi is unresolved, placed either with the G. leachi–G. longirostris clade or with the G. commissarisi clade. Distance values among G. morenoi, G. commissarisi, G. longirostris, and G. leachi were similar, suggesting a similar time of speciation for these 4 species.

We studied clinal variation in karyotypes of Peters' tent-making bat (Uroderma bilobatum) along a transect from south-central El Salvador to northwestern Nicaragua. Nondifferentially stained karyotypes were scored for 291 specimens from 5 localities. Each locality was near a locality from which similar data on U. bilobatum have been reported in the literature 18 years ago. G-tests indicated no significant differences between our data and the historical data at 2 localities in El Salvador; significant differences were found at the contact zone in Honduras. Based on a combined sample of 834 specimens, by means of the point at which genotype frequencies equal 20% and 80% (20/80 rule), we estimated that 3 chromosomal morphs (designated Aa, Bb, and Cc) had an average clinal width of 33.3 km. The widest cline, Bb, was 12.53 km wider than the narrowest, Cc. Morph Cc was detected at 2 localities, 72 and 80 km northwest of the nearest locality from which it was previously known. Overall, we detected little change in clinal architecture during the intervening years between these 2 analyses. Four investigators who used the same data set have published 4 different interpretations of clinal dynamics. These interpretations are mutually contradictory and so all cannot be correct.

We tested for a relationship between number of bat species and surface area of 20 caves in central Mexico and investigated the role of the habitat diversity model as an explanation for this relationship. There was a significant positive correlation between the logarithm of species richness and the logarithm of cave surface area, evidence of a species–area relationship. Our data suggest that roost site diversity, as indicated by spatial variation in relative humidity and presence of avons (conical depressions in cave ceilings) is a cause of the species–area relationship.