Determining occurrence and distribution is an essential 1st step in conservation planning for rare species. Spatial habitat models can be used to increase efficiency of field surveys and to improve understanding about factors influencing animal distributions. We used a modeling approach to identify and prioritize potential habitat for survey efforts for an uncommon mammal, the pygmy rabbit (Brachylagus idahoensis), for which detailed habitat data are limited. A base map of potential habitat in Idaho was defined using vegetation type and soil depth data. Documented locations (n = 164) were used to evaluate additional habitat variables to prioritize the potential habitat for surveys. We conducted field surveys to evaluate the predicted habitat attributes and document presence or absence of the species. Newly confirmed occurrences (n = 112) and absences (n = 139) were used to assess accuracy in predicting habitat priority ratings. Overall model accuracy was 65%. Eighty-four percent of the new occurrences were located in the 2 highest priority ranks, and <0.4% were located in the 2 lowest priority ranks. We offer several examples of how survey results can be used to improve the habitat model and increase efficiency of future survey efforts.

We examined the spatial and social structure of a high-altitude population of the scarcely known southern mountain cavy (Microcavia australis) in Argentina. We used radiotelemetry techniques to monitor nest use at night and daily home ranges and examine whether southern mountain cavies form nesting associations that are socially cohesive groups. We further timed our observations to breeding time of our study population (September–November) to assess opportunities for communal breeding. The nighttime telemetry of 24 radiotagged cavies revealed 7 nesting associations (i.e., communal nesting). These included 1–4 breeding females and 1 or 2 breeding males. Nesting associations were stable in terms of identity of individual members and in the location of putative nest sites. Most associations used a single nest site, but some shared 2 or 3. We noted that all nest sites were located under dominant shrubs, but use of nest sites was unrelated to variation in shrub cover. Nest sites with more burrow entrances were more frequently used by radiocollared cavies. During the day, home ranges of cavies overlapped more with ranges of nest mates than with those of non–nest mates, implying that nesting groups were socially cohesive units. This study confirmed that southern mountain cavies are communally nesting, and, because communal nesting occurs during breeding time, our findings support the idea that cavies engage in communal care of young.

Factors influencing initiation of population fluctuations of Microtus pennsylvanicus were studied in alfalfa and bluegrass habitats for 25 years. Increased survival during spring and summer appeared to be the most important factor associated with initiation of a population fluctuation. The proportion of reproductively active adult females did not influence initiation of population fluctuations. The interval between fluctuations was not correlated with density of the previous population fluctuation. We propose that population fluctuations were initiated by the net effects of relaxation of predation pressure of multiple generalist predators, which occurred erratically across years.

Calomys musculinus is the natural reservoir of Junin virus, the etiological agent of Argentine hemorrhagic fever. In this paper we measure the effective size of 2 populations of the rodent over a 2-year period. Twenty enzyme-coding loci were analyzed using vertical starch gel electrophoresis. Effective population sizes (N_es) were estimated by the pseudolikelihood method in 2 populations 280 km apart in central Argentina. Both populations experienced marked seasonal changes in relative density and in N_e (between 19.8 and infinity). Changes in percentage of polymorphic loci and mean number of alleles per locus were statistically significant and were roughly correlated with density and N_e. Observed changes in heterozygosity, in contrast, were not significant. After low-density periods, mixing of surviving individuals coming from different demes may play an important role in the maintenance of variability and recovery of N_e in populations of C. musculinus.

Population size of European otters (Lutra lutra) was estimated in Pollino National Park (southern Italy) by genetic typing of fresh feces collected in the field. Of 187 fecal samples gathered, 185 (98.9%) yielded otter DNA, 77 (41.2%) were successfully typed, and 23 different genotypes were identified. A nonlinear regression between the number of typed spraints and the cumulative number of identified genotypes was repeated after randomization of the sample until it gave an estimated otter population of 34–37 animals (0.18–0.20 otters/km of watercourse). The applied method represents a valuable conservation tool, combining the advantages of an indirect survey with the accuracy of an exhaustive census.

Most studies of animals' home-range sizes have focused on adults, and the home ranges of subadults are usually, at best, only mentioned anecdotally. In this paper we report home-range sizes of 56 philopatric sexually immature (1.5- and 2.5-year-old) brown bears (Ursus arctos) in 2 Swedish study areas and how size is influenced by sex, age, body size, food availability, and population density. Home-range size was larger in males than in females, and home-range size increased with increasing body size, but was not related to individual age. Home-range size decreased with increasing population density, but less so in females than in males, a result consistent with the formation of matrilinear assemblages recently reported in brown bears. Although home ranges were larger in the less-productive northern study area than in the southern one, home-range size was not related to a general index of food availability.

Heaviside's dolphin (Cephalorhynchus heavisidii) is a coastal delphinid with a limited inshore distribution off the west coast of southern Africa. Knowledge of its habitat usage is an essential precursor to assessing its potential vulnerability to fisheries interactions. Six Heaviside's dolphins (1 male and 5 females) were fitted with satellite-linked transmitters in 2004, and tracked for up to 54 days. The 5 tags fitted to female dolphins transmitted continuously, allowing for analysis of movements at a fine temporal scale. Four dolphins showed an initial avoidance of the capture site by moving over a wider area in the first 2–5 days posttagging than later in the deployment period. All dolphins had used their full home ranges (determined as 100% minimum convex polygons) 5–20 days before tag failure, suggesting measured home ranges were stable at this temporal scale. Home-range estimates using local convex hulls ranged from 301.9 to 1,027.6 km² (90% isopleths) and 875.9 to 1,989.6 km² using the 100% isopleths and scaled positively with body size but varied in shape, usage, and number of core-use areas. Although the distance from shore and depth at which individual dolphins moved varied greatly, all dolphins showed a strong onshore–offshore diurnal movement pattern, generally being closest inshore between 0600 h and noon, and farthest offshore between 1500 h and 0500 h. This pattern is assumed to be related to the movements of their principal prey, juvenile shallow-water hake (Merluccius capensis), which migrate into the upper water column at night. Movements inshore may be associated with rest, socializing, and predator avoidance.

Perspectives on the importance of natural salt licks to ungulates have been broadened beyond the role of providing sodium. This study examined the chemical compositions of wet and dry licks in north-central British Columbia, and defined the benefits of licks to elk (Cervus elaphus), moose (Alces alces), Stone's sheep (Ovis dalli stonei), and mountain goats (Oreamnos americanus). We analyzed soils for buffering compounds (carbonates) and estimated available elements from extractions with solutions at a low, digestive-tract pH. Even though the 2 types of licks are visually distinct, with different concentrations of chemical components, they serve similar functions as concentrated sources of sodium, carbonates, magnesium, and sulfate. Sodium and sulfate concentrations were typically higher at both wet and dry licks than control sites. Carbonates and magnesium were elevated in soils from dry licks and magnesium also was high in inflow waters to wet licks. We estimated elemental intake by ungulates from the composition of forage samples. Forages used by all 4 ungulate species were too low in sodium to meet requirements. Spring and summer forages contained high potassium levels. Licks in our study, therefore, provide ungulates with supplemental sources of sodium that are particularly beneficial to offset increasing demands during lactation and with carbonates to help stabilize rumen pH after forage changes in spring. Supplemental sources of magnesium may be actively sought by ungulates when high levels of dietary potassium affect absorption. To assess the importance of clay in soils ingested at licks, we determined the clay mineral types at licks and compared the buffering capacity of clay-filled fecal material collected at licks with fecal material collected away from licks. Further studies are needed to define the roles of clay in improving forage palatability and digestibility.

In otherwise nutrient-poor savannas, fertile vegetation patches are particularly attractive to ungulates because of the higher-quality food they provide. We investigated forage plants and diet of the common warthog (Phacochoerus africanus) on an abandoned cattle ranch in coastal Tanzania. The forage grasses of highest nutritional quality occurred in former paddock enclosures (bomas) where cattle had been herded at night. In the dry season, grass samples from bomas contained approximately 4 times as much nitrogen and phosphorus as those of the surrounding vegetation. δ¹⁵N values of soil and plants also were highest in bomas and decreased significantly with distance, and high δ¹⁵N values in feces suggest that warthogs preferentially fed in the vicinity of the former bomas. δ¹³C values of warthog feces indicate that warthogs ingested on average 83% (77–98%) C₄ grasses, with this proportion varying regionally but not seasonally. We conclude that, for medium-sized selective grazers such as warthogs, bomas represent attractive feeding grounds. We also hypothesize that by promoting nutrient turnover in these patchily distributed areas, grazing animals help to maintain them as sources of high-quality forage.

Brown bear (Ursus arctos) food habits were examined from 1,500 fecal samples collected between 1974 and 2004 in the Cantabrian Mountains of northern Spain. The most important food items were graminoids and forbs in the spring, fleshy fruits (especially bilberries) in the summer, and hard mast in the autumn and winter (especially acorns). Animal matter also was consumed throughout the year. We found differences between 3 brown bear population nuclei within the Cantabrian population, which could be of enormous interest for habitat management. We also investigated how much interannual variation in different food items influenced our diet estimates. High fluctuations among years rather than values around a mean were inherent to some food items. However, for other items, the mean seems to be a reliable descriptor. We found that the additional years of data increased the coefficient of variation associated with some of our diet estimates and suggest the existence of directional changes in brown bear food habits that have been largely neglected. Although some studies suggest that diet is fixed and not changeable, our results show that long-term diet studies may reveal changes in habitat use patterns or habitat composition for brown bears and other wildlife species. Thus, incorporating diet studies into monitoring protocols can be helpful for designing and evaluating both current and future management actions.

We report the novel occurrence of North American red squirrels (Tamiasciurus hudsonicus) feeding on spruce bark beetle (Dendroctonus rufipennis) larvae, and consider the energetic and ecological implications. Although a bark beetle outbreak was 1st noted at our study site in 1994, significant feeding on them by red squirrels was not observed until 2002, after which there was significant increase in the prevalence of autumn beetle foraging by squirrels into 2003. This increase corresponded with a decrease in spruce seed availability, the squirrels' preferred food source. Spruce bark beetles currently represent an important food source, with 73% of monitored squirrels engaged in beetle feeding in autumn 2003, providing 20% of daily energy requirements. In autumn 2002 and 2003, the density of beetle-infested trees on a squirrel's territory was a significant predictor of whether it fed on beetle larvae but not the proportion of its foraging bouts involving bark beetles. Feeding on larval spruce bark beetles by red squirrels represents a short-term solution to a climate-mediated beetle outbreak that will ultimately reduce local spruce seed production and habitat suitability for red squirrels.

Semelparity has been demonstrated in males of several species of Australian dasyurid marsupials. Although semelparity also has been reported in some species of neotropical didelphid marsupials, no study has conclusively demonstrated its occurrence based on survival rate estimates from field studies of marked individuals. In this study, we demonstrate that the survival rates of males of a Neotropical didelphid marsupial, the Brazilian gracile mouse opossum (Gracilinanus microtarsus), decrease sharply after the beginning of the breeding season in a cerrado remnant. However, mortality of the males after mating is not complete and a small percentage of them may survive to breed again in a 2nd breeding season. Examination of the demographic data presented here conclusively demonstrates that G. microtarsus is best described as partially semelparous.

As part of a captive-breeding program to restore extirpated Columbia Basin pygmy rabbits (Brachylagus idahoensis) to their native habitat in Washington, we documented mating and parental care behavior of these lagomorphs, which was previously unknown. Pygmy rabbits bred from late February through early June, and mating behavior consisted of chasing and brief copulations. Although presented with 1–4 mating partners and 1–6 mating opportunities annually, only 74% of females became pregnant each year. Unlike other lagomorphs, females dug a 16- to 35-cm natal burrow, usually separate from the residential burrow system, an average of 13 days after a successful copulation. Twenty-four days after copulation, females gave birth to 2–7 young at the entrance of the natal burrow and then covered the entrance. Females returned to nurse 1 or 2 times per day, until young emerged from burrows about 15 days after birth. Females averaged 1.3 litters per year, rarely (2%) producing 4 litters. Except for digging a natal burrow, mating and parental care in pygmy rabbits is similar to that of other lagomorphs. Understanding reproductive behavior is critical for captive breeding and reintroduction of pygmy rabbits, and efforts to reduce the consequences of genetic bottlenecks and inbreeding in captivity.

Individual vocal recognition between mothers and pups has been widely observed in pinnipeds, especially otariids. Otariids are colonial breeders; mothers suckle only their own offspring, aggressively attacking nonrelated young. Mothers alternate foraging trips with periods ashore, and at each return to the colony, mothers and pups must find each other among all the individuals of the colony. In the Australian sea lion (Neophoca cinerea), the need for a finely tuned mechanism of recognition is exacerbated by their habit of changing the nursing location over the course of lactation. We investigated potential acoustic parameters used in mother–pup recognition in Australian sea lions. We measured 11 acoustic parameters on calls of mothers and pups and found that several parameters (fundamental frequency, energy spectrum, amplitude, and frequency modulation) were highly individually specific. Discriminant analysis correctly assigned calls to individual mothers or pups with an average classification rate of 65% and 77%, respectively. Spectral features and frequency modulation were the most important features distinguishing individuals. Lastly, principal component analysis showed that calls of pups and mothers were easily distinguishable using energy spectrum and frequency modulation. Comparison with other pinniped species suggests that individual vocal identity is likely to be selected through ecological constraints such as density of the colony, degree of polygyny, likelihood of allosuckling or fostering, and degree of maternal absence during lactation.

A test was conducted to investigate if mother–infant social transmission plays a role in the acquisition of subterranean habits in the rodent Ctenomys talarum. Thirteen infants were reared by their mother in an experimental aboveground habitat that precluded burrow construction. At the age of natal dispersal, young were allowed to dig in the soil typically inhabited by the species. All experimental tuco-tucos engaged in burrowing activities after short latencies (51 s ± 35 SD). Aboveground excursions lasted a few seconds and covered short distances, and there were no significant differences between experimental and control wild tuco-tucos. The structure of the burrows constructed by experimental tuco-tucos did not substantially differ from those typical for the species. It is concluded that vertical social transmission is not essential for the development of subterranean habits in C. talarum. The results are discussed regarding growing evidence on social transmission and its alleged role during evolution.

Most studies of inbreeding depression have confounded levels of inbreeding of parents with those of offspring. We used 4 experimental groups of prairie voles (Microtus ochrogaster) in which both parents and offspring were noninbred, parents and offspring were inbred, or parents and offspring differed in their level of inbreeding. For each pair, we recorded latency to the production of the 1st litter, number of litters produced and number of young born in 120 days, litter weights from birth to weaning, and parental behavior. Noninbred parents produced more litters and young and showed shorter interlitter intervals than did inbred parents. Inbred offspring weighed less at birth and weaning. We found no significant differences in parental behaviors among groups. Our results demonstrate that inbreeding depression occurs in prairie voles, and that it may be influenced more by physiological changes in inbred parents or young than by behavioral deficiencies in inbred parents. However, larger sample sizes could reveal that parental behavior does have an effect.

We used a comparative, multimarker approach to investigate the conservation genetics of an arboreal vole (the Sonoma tree vole [Arborimus pomo]) in the Pacific Northwest of North America. We compared geographic patterns and overall levels of genetic diversity based on 55 amplified fragment length polymorphism (AFLP) loci with those based on a single, commonly used mitochondrial locus, the control region. Although examination of the control region data revealed the presence of 2 distinct mitochondrial DNA (mtDNA) clades within A. pomo (1 in the north and 1 in the south of the species' range), the nuclear perspective provided by AFLP did not reveal a similar geographic division within the species, supporting instead that A. pomo consists of a single panmictic population. Genetic diversity estimates based on the mtDNA data (gene diversity = 0.79 and 0.80 for the 2 clades) were much greater than those based on AFLP (gene diversity = 0.31 and 0.19 for the 2 clades). These contrasting results reflect inherent differences between mitochondrial and nuclear loci in mutation rate, effective population size, expected time to monophyly, and mode of inheritance, and highlight the utility of using the combination of AFLP and mtDNA when assessing the genetic status of wild populations and species of mammals, especially those of conservation concern. In the case of A. pomo, our combined AFLP and mtDNA data support the recognition of the southern Sonoma tree voles as a distinct management unit within the species.

Phylogenetic relationships were evaluated among 13 species of Neotoma based on DNA sequences from intron 2 of the nuclear alcohol dehydrogenase gene 1 (Adh1-I2). Sequences were analyzed using parsimony, likelihood, and Bayesian methods. Three major clades (I–III) consistently were recovered and relationships among taxa within 2 of the clades remained unchanged between analyses; however, relationships within clade III were largely unresolved. Average genetic divergence values were 2.12% among species, 4% between subgenera (Teonoma and Neotoma), and 5.1% between genera (Hodomys and Neotoma). Adh1-I2 sequences were concatenated with mitochondrial cytochrome-b sequences generated from the same individuals. Examination of the combined data resulted in a phylogeny whose topology was similar to that based only on cytochrome-b sequences.

Abrothrix olivaceus is the most abundant and widespread species of sigmodontine rodent in Chile. We evaluated phylogeographic relationships within A. olivaceous based on analyses of 67 specimens collected along most of the distributional range of the species. We used nucleotide sequence data from the hypervariable domain I of the mitochondrial DNA control region. Examination of our data supports a northern origin for this taxon, followed by southward dispersal. Also, we propose the occurrence of a new subspecies of A. olivaceus in the northernmost limit of the species' range. We detected a significant influence of recent paleoclimatic events on the current distribution of A. olivaceus, particularly in south-central Chile. The results also support the genetic distinctness of nominal subspecies proposed in the classical literature.

Although traditionally placed in the genus Pipistrellus, studies since the mid-1900s have shown that the western pipistrelle (P. hesperus) and eastern pipistrelle (P. subflavus), the only 2 representatives of Pipistrellus-like bats in the Western Hemisphere, do not share a most recent common ancestry with true Pipistrellus or each other. More than 20 years ago, authors recommended taxonomic revision for the American pipistrelles by placing subflavus in a separate genus called Perimyotis, and hesperus in a another separate genus called “Parastrellus.” Recently, a comprehensive study of the molecular phylogenetics of vespertilionid bats affirmed these suggested revisions. However, the name “Parastrellus” is currently unavailable according to the International Code of Zoological Nomenclature because no formal description of the genus has been provided. In this study, we provide additional morphological and genetic data demonstrating the marked divergence among hesperus, subflavus, Pipistrellus, and other Pipistrellus-like genera, and provide a formal description of a new generic name for the nominal species P. hesperus.

The pattern of development of integumentary structures and associated tissues in the megachiropteran bat Rousettus amplexicaudatus is described on the basis of 18 specimens ranging in crown–rump length (CRL) from 8.5 to 44.4 mm. The ontogenetic sample encompasses specimens that correspond to stages 16 through 22 of the phyllostomid Carollia perspicillata (late-embryonic) as well as fetal stages. Although the earlier stages of R. amplexicaudatus show little deviations in relative timing or anatomy from Carollia, later ones are increasingly different. Integumentary structures show different degrees of developmental penetrance. Derived features in embryonic stages are clearly reflected in adult structures such as a great enlargement of the handplate in relation to the footplate at the moment in which both are fully differentiated. We propose that patagium morphogenesis includes development of dactylopatagium by initial retention and posterior growth of interdigital tissue, coupled with digit elongation; and development of pro-, plagio-, and uropatagium in association with wing muscles unique to bats. Additionally, allometric trends in wingspan, total wing area, arm-wing area, and hand-wing area were estimated with respect to CRL. Changes in the terminology of some Carollia stages (16 and 18) are proposed to facilitate comparisons across bat species.

Incremental dentin and associated enamel, features visible at the surface of lower incisors of rodents, may chronicle important life-history information. This study investigated surface features of lower incisors representing 4 taxa of prairie dogs (Cynomys) in relation to hibernation and season of year. A set of abnormalities in dentin and enamel, observed on 20 of 138 incisors, always chronicled an event ending in late winter or early spring and was interpreted as a hibernation mark. Hibernation was recorded in the incisors of obligate hibernators, C. leucurus and C. gunnisoni, as well as in 20% of specimens of the facultative heterotherm, C. ludovicianus, with relevant winter growth record. Inspection of prairie dog incisors from museum collections elucidated patterns in the timing of spring emergence across species, sexes, and elevations. Growth rates of prairie dog incisors (estimated from thicknesses of circadian dentin increments) showed general seasonal patterns when pooled by sex and species, but daily growth rates recorded along individual incisors often fluctuated idiosyncratically through time. However, incisors that chronicled a significant temporal trend in daily growth rate registered either early-season (increased growth rate through time) or late-season growth (decreased growth rate through time). None of 11 late-Pleistocene fossil C. niobrarius churcherii exhibited a hibernation mark, but 4 of these exhibited significant decrease in growth rate along their incisors, probably indicating animals that died late in the active season.

The dietary niche and morphological adaptations of a species should be highly correlated. However, conflicting selective pressures may make predictions about diet difficult without additional knowledge of a species' life history. We tested the reliability of predicting a bat's diet from its wing morphology using data for Spix's disk-winged bat (Thyroptera tricolor). The species had been predicted to fall within either the aerial hawking or gleaning foraging group. We compared the results of a theoretical (canonical discriminant function analysis of morphology) and an applied (analysis of droppings) method of diet determination. Our results place T. tricolor in the gleaning functional group with a 77% probability according to morphology. Correspondingly, a large proportion of the diverse diet consisted of nonflying prey, such as spiders, insect larvae, and other silent prey, which should be difficult to detect using echolocation. Although some flying prey were taken, it is clear that T. tricolor regularly gleans prey from surfaces, indicating that for this species, morphology is a useful indicator of diet. However, the breadth of the diet; the high proportion of jumping spiders, leafhoppers, and insect larvae; and the extremely small size of prey were unique features of the diet that could not be predicted from morphology alone. Thus, although comparative statistical methods and the analysis of wing morphology may be helpful to predict the general ecological niche, only detailed investigation of the life history may yield the detail needed for understanding the link between morphology and ecology of individual species.

We compared the external morphology of western long-eared myotis (Myotis evotis) living in mountain (cool, wet) and prairie (warm, dry) environments in southern Alberta to test whether flight permits genetic exchange between populations thereby limiting divergence in morphological traits. We measured size of the body (forearm length and mass), ears, and wings for males and females. Ears and wings were significantly larger for bats in the mountains, suggesting that there is limited gene flow between populations despite their geographic proximity, and adaptation to differences in aridity or foraging habitat. However, body size was similar between environments, suggesting that either M. evotis possesses an ecologically flexible body type or that differences in extremity size are the result of environmentally induced phenotypic plasticity. Within environments, females were larger than males for all morphometrics. However, the degree of dimorphism was similar for mountain and prairie populations, indicating that dimorphism is not the result of different thermoregulatory needs in these populations.

Allometric relationships of brain and body size in the mammalian order Carnivora have been studied with respect to the pattern and timing of brain-size evolution and aspects of life history, adaptation, and ecology. Analyses of character evolution are aided by inclusion of relevant fossil data; however, endocranial volumes for fossil taxa have been limited to a few cases of extraordinary preservation, reducing the power of analyses. A method for estimating the volume of the brain from external braincase measurements of extant carnivorans is developed here. Multiple linear regression, combined with Akaike information criterion–based model averaging, was employed to predict endocranial volume from 3 external skull measures for 825 museum specimens of 126 extant terrestrial taxa spanning the Carnivora. The AIC-averaged model accurately predicted endocranial volumes for carnivoran taxa (R² = 0.983), and the results were robust to potential sampling problems. Moreover, the model did not reflect phylogenetic autocorrelation, nor did it represent an induced correlation due to a general body-size scaling. Rather, the averaged model was an accurate predictor of brain volume that should be easily extendable to the carnivoran fossil record, and additionally can be generalized to construct similar models for a broad range of mammalian clades. This in turn will allow comparative studies within and among distantly related mammalian lineages and reconstructions of brain volumes for a diverse array of fossil taxa.

We describe a partial skeleton of a new species of Bubalus (Bubalus) from soft karst near Balamban, Cebu Island, Philippines. The specimen is likely Pleistocene or Holocene in age and includes left and right humeri, a left metatarsal, 2 posterior thoracic vertebrae, 2 left lower molars, and a pair of ungual phalanges. Bubalus sp. nov. differs from all previously described Bubalus in both the size and proportions of the skeleton and in possessing a unique combination of discrete character states. Possible autapomorphies for Bubalus sp. nov. evident in the metatarsal include a very broad dorsal longitudinal sulcus; a broad, triangular anterior cubonavicular facet; and a sulcus that bisects a small tuberosity on the proximolateral surface. Limb elements of Bubalus sp. nov. are less than two-thirds the length of corresponding elements of the Asiatic water buffalo, B. (Bubalus) bubalis, and are about 80% the length of those of the tamaraw, B. (Bubalus) mindorensis; they are similar in length to limb bones of the lowland anoa, B. (Anoa) depressicornis, but are more robust. Mass estimates based on regression equations for modern bovids suggests a mass of 150–165 kg for Bubalus sp. nov.; this is approximately 25% smaller than B. mindorensis (180–220 kg) and at least 15% larger than B. depressicornis (approximately 135 kg). The small size of Bubalus sp. nov. relative to other B. (Bubalus) is likely attributable to island dwarfing; this is supported by a consistent relationship between body size and island size in Bubalus sp. nov., B. mindorensis, and B. bubalis, and by the relatively larger dentition of B. sp. nov. relative to body size. Bubalus sp. nov. is the 1st fossil mammal to be reported from Cebu Island and is the only nonproboscidean documented from the Negros–Panay Philippine Faunal Region. In conjunction with the presence of Bubalus on Mindoro Island (and potentially Luzon), this specimen suggests that Bubalus may once have ranged throughout the Philippines.