Genetic architecture and evolution of color variation in American black bears.

Color variation is a frequent evolutionary substrate for camouflage in small mammals, but the underlying genetics and evolutionary forces that drive color variation in natural populations of large mammals are mostly unexplained. The American black bear, Ursus americanus (U. americanus), exhibits a range of colors including the cinnamon morph, which has a similar color to the brown bear, U. arctos, and is found at high frequency in the American southwest. Reflectance and chemical melanin measurements showed little distinction between U. arctos and cinnamon U. americanus individuals. We used a genome-wide association for hair color as a quantitative trait in 151 U. americanus individuals and identified a single major locus (p < 10-13). Additional genomic and functional studies identified a missense alteration (R153C) in Tyrosinase-related protein 1 (TYRP1) that likely affects binding of the zinc cofactor, impairs protein localization, and results in decreased pigment production. Population genetic analyses and demographic modeling indicated that the R153C variant arose 9.36 kya in a southwestern population where it likely provided a selective advantage, spreading both northwards and eastwards by gene flow. A different TYRP1 allele, R114C, contributes to the characteristic brown color of U. arctos but is not fixed across the range.

COMPARISON OF ISOFLURANE GAS VERSUS A GUAIFENESIN, KETAMINE, AND MEDETOMIDINE CONSTANT-RATE INFUSION FOR MAINTENANCE ANESTHESIA IN AMERICAN BLACK BEARS (URSUS AMERICANUS).

Published anesthetic protocols for captive and free-ranging bears are limited to injectable inductions with maintenance via inhalants or additional injectable boluses. Though common in other species, intravenous (IV) continuous-rate infusions (CRI) using guaifenesin combinations have not been evaluated in ursids. This study evaluated the use of a CRI compared to an inhalant for maintenance anesthesia. Seven healthy American black bears (Ursus americanus) were anesthetized in a crossover design with two different anesthetic maintenance protocols. Bears were immobilized with ketamine (2.02 ± 0.14 mg/kg) and medetomidine (0.04 ± 0.003 mg/kg) for both protocols. The anesthetic maintenance control protocol consisted of isoflurane gas (ISO) started at 2% delivered by endotracheal tube; the experimental protocol consisted of guaifenesin, medetomidine, ketamine (GMK) IV CRI started at 50 mg/kg/hr guaifenesin, 0.01 mg/kg/hr medetomidine, and 1 mg/kg/hr ketamine. Induction and recovery parameters including time to first effect, recumbency, and hands on; duration of maintenance protocol; and time from reversals administered to head up, standing on all four feet, no ataxia, and to fully recovered were recorded and compared between protocols. Heart rate, respiratory rate, rectal temperature, blood pressure, end tidal carbon dioxide, and hemoglobin oxygen saturation were recorded at 5-min intervals and compared between protocols. Venous blood gases were obtained at the start, middle, and end of the maintenance anesthesia and compared between protocols. All bears exhibited hypertension with mild respiratory acidosis throughout procedures. Measured physiologic parameters did not differ significantly between the isoflurane and the GMK CRI maintenance protocols, with the exception of higher endpoint (ISO) pCO2 measurements. No adverse events were recorded with either protocol, and adequate depth of anesthesia was maintained with both protocols. GMK CRI provides a safe, effective, and more portable alternative to inhalant anesthetics for maintenance anesthesia in bears in captivity or in the field.

Spatial genetic structure in American black bears (Ursus americanus): female philopatry is variable and related to population history.

Previously, American black bears (Ursus americanus) were thought to follow the pattern of female philopatry and male-biased dispersal. However, recent studies have identified deviations from this pattern. Such flexibility in dispersal patterns can allow individuals greater ability to acclimate to changing environments. We explored dispersal and spatial genetic relatedness patterns across ten black bear populations-including long established (historic), with known reproduction >50 years ago, and newly established (recent) populations, with reproduction recorded <50 years ago-in the Interior Highlands and Southern Appalachian Mountains, United States. We used spatially explicit, individual-based genetic simulations to model gene flow under scenarios with varying levels of population density, genetic diversity, and female philopatry. Using measures of genetic distance and spatial autocorrelation, we compared metrics between sexes, between population types (historic and recent), and among simulated scenarios which varied in density, genetic diversity, and sex-biased philopatry. In empirical populations, females in recent populations exhibited stronger patterns of isolation-by-distance (IBD) than females and males in historic populations. In simulated populations, low-density populations had a stronger indication of IBD than medium- to high-density populations; however, this effect varied in empirical populations. Condition-dependent dispersal strategies may permit species to cope with novel conditions and rapidly expand populations. Pattern-process modeling can provide qualitative and quantitative means to explore variable dispersal patterns, and could be employed in other species, particularly to anticipate range shifts in response to changing climate and habitat conditions.

Demographic characteristics and infectious diseases of a population of American black bears in Humboldt County, California.

American black bears (Ursus americanus) are common, widely distributed, and broad-ranging omnivorous mammals in northern California forests. Bears may be susceptible to pathogens infecting both domestic animals and humans. Monitoring bear populations, particularly in changing ecosystems, is important to understanding ecological features that could affect bear population health and influence the likelihood that bears may cause adverse impacts on humans. In all, 321 bears were captured between May, 2001, and October, 2003, and blood samples were collected and tested for multiple zoonotic and vector-borne diseases. We found a PCR prevalence of 10% for Anaplasma phagocytophilum, and a seroprevalence of 28% for Toxoplasma gondii, 26% for Borrelia burgdorferi, 26% for A. phagocytophilum, 8% for Trichinella spiralis, 8% for Francisella tularensis and 1% for Yersinia pestis. In addition, we tested bears for pathogens of domestic dogs and found a seroprevalence of 15% for canine distemper virus and 0.6% for canine parvovirus. Our findings show that black bears can become infected with pathogens that are an important public health concern, as well as pathogens that can affect both domestic animals and other wildlife species.