The cache decisions of scatter-hoarding animals are influenced by a number of factors, including satiety, food quality, number of competitors, and the risk of predation and pilferage. However, it is unknown how animals assess these variables. We investigated this process experimentally in free-ranging fox squirrels (Sciurus niger) by measuring the effects of nut characteristics and social context on nut-handling behavior and subsequent cache decisions. We found that a behavior involved in nut handling, the head flick, was correlated with nut quality, shell presence, the decision to cache rather than eat the nut, and the time and energy spent caching. In contrast, a 2nd nut-handling behavior, the paw maneuver, was correlated with the social context but not the cache decision, and may instead reflect a response to social competition. Our results suggest that fox squirrels assess nut quality using overt, observable nut-handling behaviors. The experimental study of these behaviors can help us understand how animals use information about food and the social context to make adaptive food-storing decisions.

Scatter-hoarding animals store food items to be used later when food is scarce. However, other individuals can pilfer food stores because caches are not usually defended. We tested how associative learning contributes to foraging success of pilferers searching for scatter-hoarded food. We conducted a field-based, seed-removal experiment to test 2 hypotheses. First, yellow pine chipmunks (Tamias amoenus) will learn to associate buried food with recurring objects faster than they will learn to associate food with singular (distinctive) objects. Second, they will learn to associate buried food with man-made objects faster than they will learn to associate food with natural objects. Rodents clearly learned to associate objects with buried food regardless of distinctiveness or origin. The observed pattern of seed removal suggested that high relative humidity (RH) events (storm systems) increased seed odor, facilitating olfaction by rodents, and increasing the rate of seed removal. We tested this hypothesis in a laboratory experiment using 8 wild-caught yellow pine chipmunks and 5 levels of RH (17%, ∼27%, ∼50%, ∼75%, or ∼95%). Foraging success at 17–75% RH was not different from random, but at 95% RH seed recovery was significantly higher than random. High RH facilitates discovery of buried seeds, and with higher foraging success, associative learning of cache markers may be easier. Thus, cache pilfering may be facilitated by high humidity.

We hypothesized that caching could be a mechanism to remove volatile secondary compounds from a plant-based diet. This mechanism has been demonstrated in 1 herbivore and has been hypothesized as a widespread mechanism for reduction of intake of toxins. We examined this hypothesis in both the field and the laboratory by documenting the ability of herbivorous rodents to manipulate alpha-pinene, the major terpene in juniper (Juniperus osteosperma). First, we dismantled middens of Neotoma albigula and found that cached plant material was devoid of alpha-pinene, whereas surrounding trees contained alpha-pinene. In laboratory trials, we examined the ability of woodrat species (N. albigula, N. lepida, and N. bryanti) to reduce toxin intake by storing food before consumption. Each species responded differently when offered terpene-treated pellets. N. albigula controlled terpene intake by increasing reliance on the terpene-free cache. N. lepida controlled terpene intake by decreasing total intake but did not change cache consumption. N. bryanti did not regulate terpene intake. All 3 species abandoned more food in the foraging cage when the food contained terpene. In an additional laboratory trial with N. albigula, we determined that increased abandonment was not related to cache size.

We studied the spatial organization of dusky-footed woodrats (Neotoma fuscipes) in mixed-conifer forest of the northern Sierra Nevada, California, by radiotracking 63 adult woodrats at 2 study sites during May–October 2004–2006. Estimates of home-range and core-area size differed between study sites, but they were within the range reported elsewhere; variability in home-range size was explained in part by density. Home ranges of woodrats overlapped those of multiple neighboring woodrats, both same sex and opposite sex, suggesting that foraging areas were shared. However, core areas showed little overlap between same-sex neighbors. Woodrats occupied multiple houses and frequently moved among them, and sharing of houses (either simultaneously or nonsimultaneously) with neighboring woodrats was common but occurred mostly between male–female pairs. Females typically shared their core area and houses with 1 male, whereas males shared core areas and houses with multiple females; further, males moved more than females. Our results suggest that dusky-footed woodrats are semiterritorial, maintaining near-exclusive use of their core area and houses against same-sex conspecifics, and that the mating system likely is polygynous.

Two hundred twenty-two individuals of the southern plains woodrat (Neotoma micropus) were captured from 198 excavated middens at 10 discrete collecting sites from a single population in south-central Texas. Field data, mitochondrial D-loop haplotypes, and polymorphic microsatellite loci (5–7) were used to determine genetic patterns in parentage, relatedness, and mating strategy. Microsatellite loci were highly polymorphic (average observed heterozygosity  =  0.859) and were used to construct genotypes that were unique for each individual (probability of identical genotypes: 1 in 2,104,567). Results indicated a high frequency of multiple paternity (6 of 9 litters), evidence of repeat mating between the same 2 individuals, and no indication of male dominance at any collection site. Examination of these data suggested a promiscuous mating system. Within a site, average relatedness between adult females was similar to that between adult males. A higher level of cohabitation from that previously documented was recorded and finer-scale analyses revealed high levels of relatedness between most cohabiting individuals. Taken with results from other studies of mating behaviors of N. micropus, our results suggest that mating and social behavior of this species are likely influenced by population density.

Northern rodent populations often exhibit temporal dynamics due to seasonal changes in demographic processes such as survival, reproduction, and movement. Seasonal patterns in their demography partially result from seasonal changes in climate and resource availability. We studied the population ecology of Mongolian gerbils (Meriones unguiculatus), a social rodent living in groups year-round in desert grasslands of China, Mongolia, and Russia, using capture–recapture methods to investigate seasonal patterns in demography. Gerbils were livetrapped biweekly from late April to late October 2006 in Inner Mongolian grasslands, China. We used robust-design models and Cormack–Jolly–Seber models to estimate population size and apparent survival probability. Additionally, we used multistate models to test for a trade-off between reproduction and survival. Like other northern rodents, Mongolian gerbils showed a single annual peak in abundance, but gerbil numbers peaked unusually early in June. Gerbil populations were female-biased and also biased toward older individuals. The breeding season was restricted to the wet season from April to the end of August, and survival declined from April to October. We found a trade-off between survival and reproduction in males but not in females. Kinship and cooperation among females may enhance survival to offset the cost of reproduction.

Recent increases in hurricane activity along the Gulf of Mexico lend urgency to understanding storm impacts on beach mice (Peromyscus polionotus) that occupy dune systems along this coast in Florida and Alabama. We documented changes in occupancy patterns of the Santa Rosa beach mouse (P. p. leucocephalus) from Hurricane Ivan and examined predictors of habitat use before and after the hurricane. The hurricane removed 68% of frontal dune area occupied by beach mice and only 15% of scrub dune area. Occupancy of frontal dunes by beach mice dropped from 100% before to the hurricane to 60% after the hurricane. Occupancy of scrub habitat was lower than occupancy of frontal dune habitat before the hurricane (∼75% occupancy) and did not change with the hurricane. Occupancy of frontal dunes after the hurricane was influenced by percent cover of woody vegetation, dune height, and distance to nearest occupied dune. Probability of occupancy of scrub habitat was positively correlated with individual dune area and amount of surrounding dune habitat before and after the hurricane. Our study supports recent efforts to define scrub dunes as Critical Habitat for beach mice and points to the importance of enhancing dune height and reducing dune isolation in coastal restoration programs.

Using data from a 28-month capture–mark–recapture study that included 3 winters, we compared rates of body growth and survival for a population of hispid cotton rats (Sigmodon hispidus) in eastern Virginia with another marginal population in eastern Kansas, and where possible, with southern populations in coastal Texas and central Florida. Patterns of seasonal growth were similar in Virginia and Kansas, being low, often near 0, in winter but moderate in other seasons, unlike the uniform seasonal growth rates in Texas. Survival rates were similar between the sexes in both Virginia and Kansas but the overall monthly survival rate in Kansas (0.75) was much higher than the means for Virginia (0.69 for females and 0.62 for males). In sum, despite mild and mostly snow-free winters in eastern Virginia, the patterns of body mass and rates of growth and survival were more similar to those of Kansas populations than to those of cotton rat populations from Texas or Florida.

The distribution and taxonomic status of the Alaska marmot (Marmota broweri) have been the subject of much debate and confusion since the taxon was 1st described as a subspecies of the hoary marmot (M. caligata). As a result of its early association with M. caligata and a lack of focused effort to determine its range, our current understanding of the distribution of M. broweri is vague at best and completely erroneous at worst. Through a review of all museum specimens and published accounts of this species, field surveys, and the identification of previously unidentified marmot specimens, we have determined that the current distribution of the Alaska marmot includes not only the Brooks Range, but also the Ray Mountains and Kokrines Hills of northern interior Alaska. We report the 1st confirmed records of this species outside of the Brooks Range and a commensurate range extension of 400 km southward. The Yukon River appears to form the current boundary between the parapatric distributions of M. broweri and M. caligata in Alaska, but additional fieldwork will be necessary to confirm that the 2 species are not allopatric.

Snowshoe hares (Lepus americanus) are widespread in boreal and montane forests of North America, vary in their temporal dynamics, and are major drivers in their food webs. In Yellowstone National Park, Wyoming, hare abundance, distribution, and temporal dynamics are unknown, yet Yellowstone contains a large area within their southern range that is relatively unfragmented by human activities. The 1988 Yellowstone fires have led to extensive regenerating stands, a seral condition that elsewhere supports relatively high numbers of hares. To examine snowshoe hare dynamics in the park from 2002 to 2007, we surveyed stands within 7 cover types and estimated abundance for a subset of sites. Both livetrapping data and fecal pellet count surveys showed that snowshoe hares are rare in Yellowstone. More than 36% of surveyed stands did not support any hares. Mature forest cover types were more likely to have hares than were stands regenerating after the 1988 fires, but very few stands supported high numbers; 96% of stands had <0.5 hares/ha. Three stands that burned in 2003 had hares before the fire, but none afterward. Hare numbers fluctuated modestly over time, but patterns were not indicative of a cycle. Taken altogether, our results indicate that snowshoe hares in Yellowstone are rare, patchily distributed, and apparently acyclic, important findings both for understanding hare dynamics and for implications for the Yellowstone food web that includes the federally Threatened Canada lynx (Lynx canadensis).

Ecomorphological studies reveal the coexistence of many phenotypically similar bat species. If competition theory is correct, these species should occupy different niches. Here we investigate whether 2 sympatric sibling species of insectivorous bats, Scotophilus dinganii and Scotophilus mhlanganii, that are similar in morphology also occupy similar niches as predicted by the ecomorphological paradigm. The only phenotypic differences we found between the 2 species were a 10-kHz difference in their echolocation frequencies (S. mhlanganii 42.6 ± 1.6 kHz; S. dinganii 33.7 0 ± 1.8 kHz) and a higher wing loading in S. mhlanganii (15.5 ± 2.3 N/m²) compared to S. dinganii (13.6 ± 1.5 N/m²) as a result of the former's similar mass but shorter wingspan. However, there was much overlap in the wing parameters, including wing loading, of the 2 species. In support of the ecomorphological paradigm, the similarity in their phenotypes was reflected in the absence of any detectable spatial or temporal differences in their habitat use (determined by radiotelemetry). Furthermore, subtle differences in skull morphology were correlated with subtle differences in the size of dietary items eaten. S. dinganii, with its larger skull, ate a wider range of insect prey sizes (11.2–18.9 mm) than S. mhlanganii (11.6–12.2 mm). The most profound ecological difference between the 2 species was the use of different roosts. S. dinganii always was found in building roosts and S. mhlanganii always in trees. Thus, the ecological similarities with their phenotypic correlates support the ecomorphological paradigm. Assortative mating, resulting from the use of different roosts, combined with genetic drift, may explain the subtle differences reported here.

In response to the rapid decline of greater horseshoe bats (Rhinolophus ferrumequinum) in Europe, conservation efforts have previously focused on protecting maternity roosts and hibernacula. Currently, there is little information available on the ecology of this species outside of these 2 main periods. This study investigates patterns of roost use, ranging behavior, habitat use, and diet of R. ferrumequinum using data collected from a transitional roost studied over 3 years in Dorset, United Kingdom. The roost was predominantly used during the spring and autumn, and acted as a link between maternity roosts and hibernacula. Compositional analysis of ranging behavior collected in the spring revealed that R. ferrumequinum selected grazed pastures and broad-leaved woodland compared with other available habitat. Diet analysis revealed that there was little difference between the diet of individuals using the transitional roost and the nearest known R. ferrumequinum maternity colony. Broad-leaved woodlands within 4 km of transitional roosts used by R. ferrumequinum in the spring should be protected to help conserve this species.

Historic fur returns from Hudson's Bay Company posts in northwestern Canada reveal periodic oscillations in mink (Neovision vision) harvests lagging 2–3 years behind oscillations in muskrat (Ondatra zibethicus) harvests, as would be expected in a predator–prey interaction. Toward central and eastern Canada, the strength of the interaction between time series of harvests of minks and muskrats weakens and the lag between fluctuations of these 2 species decreases to 1 and 0 years, respectively. We tested the hypothesis that this gradient in mink–muskrat interactions is the result of decreased dependency of minks on muskrats in areas where minks have access to more alternate prey. We tested 2 predictions: species richness of mink prey is greatest in eastern Canada and decreases to the west, and percent muskrats in the diets of minks decreases as species richness of mink prey increases. Contrary to the 1st prediction, we found that species richness of mink prey in Canada is highest in south-central Canada. Consistent with the 2nd prediction, percent occurrence of muskrats in the diets of minks was much lower in areas with greater species richness of mink prey. Local species richness of mink prey therefore could influence the degree of specialization of minks on muskrats, but may be insufficient to explain the geographic pattern in the lag between muskrat and mink harvests in eastern Canada.

Sea otter (Enhydra lutris kenyoni) movements, home range, and activity budgets were described from data collected during very-high-frequency radiotelemetry studies of 75 individuals on the outer coast of Washington State between 1992 and 1999. Sea otters were located at least once per week from 22 accessible sites along the coast. Over the 7-year study period, range expansion occurred from the core range north and east into the Strait of Juan de Fuca (SJF) as well as southward on the outer coast. Forty-three percent of the sea otters moved into the SJF at least once, most often in winter, using habitat that had not been occupied by sea otters since their extirpation 100 years ago. All sea otters spent portions of their time in the vicinity of Cape Alava, and many animals demonstrated consistent periodic seasonal shifts between specific portions of the coastline over several years. Ninety-five percent annual linear home ranges differed between sex and age classes. Adult males used the largest amount of coastline (50 km ± 9 SD) and subadult females used the least (24 ± 9 km). Both adult males and females demonstrated high seasonal periodicity in range use in summer and winter. Twenty-four–hour time budgets in the core portion of the range revealed on average sea otters spent 41% ± 14% SD of the time foraging and 45% ± 13% of the time resting (age and sex classes pooled). Adult and subadult female sea otters were most frequently found resting and foraging close to shore (<1,000 m) and in shallow water (0–10 m), whereas adult and subadult males rested and foraged >1,000 m offshore and at depths between 10 and 30 m. Given current rates of population growth and observed mobility, sea otters in Washington have high potential for range expansion into unoccupied habitat such as Grays Harbor, Willapa Bay, the SJF, or along Vancouver Island.

One of the goals of the Florida panther (Puma concolor coryi) recovery plan is to expand panther range north of the Caloosahatchee River in central Florida. Our objective was to evaluate the potential of that region to support panthers. We used a geographic information system and the Mahalanobis distance statistic to develop a habitat model based on landscape characteristics associated with panther home ranges. We used cross-validation and an independent telemetry data set to test the habitat model. We also conducted a least-cost path analysis to identify potential habitat linkages and to provide a relative measure of connectivity among habitat patches. Variables in our model were paved road density, major highways, human population density, percentage of the area permanently or semipermanently flooded, and percentage of the area in natural land cover. Our model clearly identified habitat typical of that found within panther home ranges based on model testing with recent telemetry data. We identified 4 potential translocation sites that may support a total of approximately 36 panthers. Although we identified potential habitat linkages, our least-cost path analyses highlighted the extreme isolation of panther habitat in portions of the study area. Human intervention will likely be required if the goal is to establish female panthers north of the Caloosahatchee in the near term.

Knowing the factors that affect the abundance and activity patterns of pumas (Puma concolor) in South American forests may help in their conservation. Using camera traps, we conducted 4 surveys in 3 areas with different levels of protection against poaching and logging within the biggest continuous fragment of the Upper Parana Atlantic Forest. We used capture–mark–recapture population models to estimate the density of pumas for each area. The core area of Iguazú National Park, with low poaching pressure and no logging for >60 years, had the highest density of pumas (between 1.55 and 2.89 individuals/100 km²). Yabotí Biosphere Reserve, an area with the highest poaching and logging pressure, showed the lowest density (between 0.3 and 0.74 individuals/100 km²). Areas with intermediate levels of poaching and logging pressure had densities between 0.66 and 2.19 individuals/100 km². Puma activity peaked during the 1st hours of morning in the most protected area, but became more crepuscular and nocturnal in areas with less protection. The lower abundance of pumas in the more degraded areas may be related to lower prey abundance. Differences in activity patterns of pumas among areas with different poaching pressures may be a direct response to poaching or to changes in the availability and activity patterns of primary prey. Conservation efforts should focus on decreasing poaching and logging pressures within protected areas to benefit pumas and other endangered species in the Atlantic Forest.

The Pantanal of Brazil is an important area for the conservation of jaguars (Panthera onca). As the size of traditional large ranches in the Pantanal decreases, human access to jaguar habitat increases, resulting in human-altered landscapes that may influence patterns of resource selection and space use by jaguars. We used global positioning system radiocollars to study jaguars in the southern Pantanal. We radiocollared 10 jaguars (6 males and 4 females), obtained 11,787 locations, and examined their space use, movement rates, and social interactions between October 2001 and April 2004. Estimates of 90% kernel home ranges varied among animals and seasons (range: 34.1–262.9 km²). Core areas (50% isopleth) of both females and males did not differ in size between seasons, but home ranges (90% isopleth) during the dry season were generally larger than during the wet season. The stability of home ranges varied among seasons and individuals. Some females maintained ≥80% of their home ranges from 1 season to the next, whereas other females used ≤50% of their home ranges from the previous season. Site fidelity within individual home ranges also varied; ≥70% of the core areas of some females were located in different sites within their home ranges during different seasons. Locations of females suggested a pattern of spatial avoidance among females during the wet season. Home-range overlap among males was extensive, both in the wet and dry seasons, suggesting that males did not maintain exclusive ranges. Overlap between males and females occurred both in the wet and dry seasons, and movements by females were not restricted within the ranges of individual males. Jaguars were located <200 m apart more often than expected, suggesting some degree of sociality. The reproductive profiles of females suggested either a low conception rate, a low survival rate of young, or that jaguars may be more social than previously thought. Interactions among males also suggested some degree of sociality.

We used genetic-based paternity assignments from 3 diverse populations of white-tailed deer (Odocoileus virginianus) to evaluate the long-held assumption that male reproductive success in this species is highly skewed toward a small number of mature, dominant individuals. The study populations represented a range of adult sex ratios and male age structures. Male reproductive success was distributed among a large number of males in all populations, with no evidence for highly skewed access to mating for any individual male. Surprisingly, physically immature males (1.5 and 2.5 years of age) collectively fathered 30–33% of offspring in all populations, even where mature males were present. Ecological and behavioral variables appear to constrain the ability of individual males to monopolize access to females, resulting in a wider distribution of reproductive success than expected based on previous ecological and behavioral studies of white-tailed deer. Qualitative differences in the distribution of male reproductive success among study sites suggested that demographic attributes such as adult sex ratio and male age structure might influence the degree of competition for mates. Further study incorporating known-age cohorts or integrating movements and behavior is necessary for understanding the effects of population demographics as well as the physical and behavioral attributes that confer reproductive success in diverse populations of white-tailed deer.

Studying between-sex differences in body growth has strong implications for understanding life-history tactics of animals. We used age and carcass mass data from 2,312 female and 2,622 male alpine chamois (Rupicapra rupicapra) harvested in the French Alps to model the sex-specific body growth patterns of this species. Males were heavier (asymptotic body mass: 29.6 kg) than females (22.3 kg), with an adult sexual size dimorphism of 32.4%. Sexual size dimorphism originated from both differences in body growth after 1.5 years of age and differences in length of the growth period. Females reached asymptotic body mass almost 3 years earlier (3.5 years) than males (6.2 years). We also found that females 1st reproduced before achieving asymptotic growth, at 78% of their asymptotic body mass. Between-sex differences in growth patterns in this species are most likely due to stronger selection pressure for larger size in males than in females due to intrasexual competition.

Although herbivores are generally known to trade off forage in open habitat patches and cover in forested habitat patches, it remains unclear if high population density and low predation risk can modulate the trade-off between forage and cover. We studied a population of white-tailed deer (Odocoileus virginianus) that was at high density and on a large island free of predators to assess the influence of forage and cover on habitat selection under harsh environmental conditions. We fitted 19 female white-tailed deer with global positioning system collars and delineated summer home ranges and core areas. We sampled vegetation in the core areas and in the rest of the home ranges to determine abundance of forage and forest cover within habitat patches, and assessed habitat selection between open and forested habitat patches. At a coarse scale, white-tailed deer preferred open habitat patches over forested ones, suggesting that they adopted a foraging strategy favoring energy intake. At a fine scale, habitat selection was influenced positively by the percentage of ground cover of forbs and deciduous shrubs, but negatively by conifer density. The biomass of preferred plant species, lateral cover, fir regeneration, and distance to the nearest open–forest edge were not strong predictors of habitat selection by deer. We conclude that fine-scale habitat selection by white-tailed deer at high population density and in the absence of predation is mainly determined by forage abundance. These patterns of habitat selection demonstrate that herbivores can adjust their behavior to other limiting factors when predation risk is relaxed.

The forage-selection hypothesis (FSH) explains sexual segregation in ungulates as a function of different dietary requirements producing different levels of habitat optimality, whereas the reproductive-strategy hypothesis (RSH) explains sexual segregation as a function of different survival strategies between the sexes. Based on observations of habitat use by elk (Cervus elaphus) in Yellowstone National Park, Wyoming with regard to varying levels of wolf encounter risk, we found that our determination of whether the RSH or FSH best applied to sexual segregation varied by the scale at which we were measuring habitat use. At broad spatial scales we found no significant avoidance of wolves by elk. At the habitat scale we found that habitat use by elk was consistent with predictions of the reproductive strategy in that female elk used habitats that offered a balance of forage and escape terrain for themselves and calves, and that the degree to which escape terrain was present was dependent upon the risk of wolf encounter. At the scale of the habitat patch we found that differences in forage availability likely drove the differences in habitat use. Our results highlight the importance of scale when investigating habitat use, nonlethal predation effects, and sexual segregation in ungulates.

We report 3 new species of bats of the genus Murina from Taiwan. One is a larger species that closely resembles Murina leucogaster and Murina rubex both externally and cranially. However, this new species differs from either or both of the latter 2 species in the color of the face and the dorsum, the attachment point of the plagiopatagium, the shape of the upper canine, and dimensions of the skull. The other 2 new species are smaller and differ from each other in the dorsal coloration, brightness of the pelage and the face, the shape of the basioccipital pit, the shape of the 1st upper premolar, and dimensions of the skull. These 2 new species can be distinguished from all known species of Murina by either the body size, the pelage coloration, the shape of the ear, or relative sizes and shapes of various teeth in both upper and lower toothrows, or a combination of these characters.

The kangaroo rat Dipodomys merriami occurs widely over the Baja California peninsula, inhabiting all the arid and sandy lowlands. Its range encompasses diverse climatic, edaphic, and vegetation zones, including 2 islands. The 11 taxa recognized in the merriami complex in this region almost 50 years ago remain valid to the present. The 2 island forms originally were described as different species, and have been treated in different ways by subsequent authors. In this investigation we used a genetic analysis of 2 mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit III (COIII), to study patterns of genetic structuring in this species throughout the peninsula. We supplemented existing morphometric and pelage color data with new data, and integrated these data sets into a phylogenetic analysis. Finally, we explored how our results compared with the existing taxonomic arrangement of species and subspecies. Our phylogenetic analyses of molecular data used the concatenation of 1,140 base pairs (bp) of the Cytb gene and 690 bp of the COIII gene; cladograms were generated using maximum-parsimony, maximum-likelihood, and Bayesian inference procedures. A hierarchy of nested clades was produced, the highest level of which revealed 2 reciprocally monophyletic clades separated by 20 mutational steps. There is a Southern Clade extending north to the Vizcaíno Desert in the west and San José Island in the east, and a Northern Clade that includes all the populations farther to the north. At a shallower level, the Southern Clade contains 4 subclades, including the populations of San José and Margarita islands, whereas the Northern Clade is composed of 3 subclades. Adding the morphometric and pelage coloration data sets to the analyses resulted in support for the 11 previously recognized taxa arranged in a single species, Dipodomys merriami, but with improved understanding of how the subspecies relate to each other. As is increasingly appreciated, our investigation supports a comprehensive approach involving multiple data sets that are sensitive to a wide temporal range of evolutionary history for phylogenetic reconstruction.

I document odontometric variation across ground-dwelling squirrels of the Holarctic tribe Marmotini. Dental size, which correlates well with published average body mass values across species, accounts for most odontometric variation across the clade. Dental shape variation primarily reflects relative size of P3 (upper cheek teeth) and relative width of p4–m1 length of m3 (lower cheek teeth). Shape variables and relative tooth crown height covary significantly across species, suggesting a common functional complex or shared genetic control. When dental morphology is mapped on published DNA-based phylogenies, Sciurotamias (Chinese rock squirrels), Ammospermophilus (antelope squirrels), and basal subgenera within Spermophilus (ground squirrels [Callospermophilus and Otospermophilus]) are shown to retain inferred primitive dental morphology—small to moderate dental size, relatively small P3, relatively narrow p4–m1 shortened m3, and relatively low tooth-crown height. Other clades depart from this morphotype in size (very small in Tamias [chipmunks] and very large in Marmota [marmots]), tooth shape (especially 2 clades representing Eurasian and North American subgenus Spermophilus), or in both attributes (notably Cynomys [prairie dogs]), with frequent homoplasy. A plot of odontometric distance against published estimates of divergence time between sister clades suggests a roughly “clocklike” accumulation of odontometric change through time but highlights episodes of rapid odontometric evolution during the origins of Marmota, Cynomys, and Spermophilus parryii (arctic ground squirrel).

The collared tuco-tuco, Ctenomys torquatus Lichtenstein, 1830 (Ctenomyidae), is a subterranean rodent that occurs in grassland habitats of southern Brazil and northern Uruguay. A population of collared tuco-tucos located in Alegrete Municipality, Rio Grande do Sul State, Brazil, has been proposed as a potential new species because of their remarkable differences in chromosome number and their unique patterns of pelage coloration. The aim of this work was to evaluate the degree of genetic differentiation of this population using mitochondrial DNA (mtDNA) sequences and nuclear microsatellite markers, and to describe spatial patterns of genetic diversity for the other 5 populations of C. torquatus in southern Brazil, focusing on patterns of intra- and interpopulation variation in coat color. The analysis of 1,110 base pairs of the mtDNA cytochrome-b (Cytb) gene and 9 nuclear microsatellite loci revealed 7 haplotypes (n  =  65) and 48 alleles (n  =  70), respectively. Genetic diversity was moderately low within populations (H_E  =  0.40–0.56), and significantly partitioned among locations (R_ST  =  0.21; P < 0.01). Analysis of the microsatellite data suggested that genetic differentiation is consistent with a simple model of isolation by distance (r  =  0.56, P < 0.05), and that the population is in equilibrium between gene flow and local genetic drift. The partially reconstructed phylogeny revealed that the haplotypes derived from the Alegrete population were not reciprocally monophyletic, and that there was a lack of structure for coat color and karyotype variation. Thus, the individuals from the Alegrete population fall within the range of variation for C. torquatus, and should not be considered a new species. We suggest that they be considered a local, specialized lineage that could be treated and managed from a conservation perspective as a Management Unit.