Steven G. Torres

Genetic structure of mountain lion (Puma concolor) populations in California

Analysis of 12 microsatellite loci from431 mountain lions (Puma concolor)revealed distinct genetic subdivision that wasassociated with geographic barriers andisolation by distance in California. Levels ofgenetic variation differed among geographicregions, and mountain lions that inhabitedcoastal areas exhibited less heterozygositythan those sampled inland. The San FranciscoBay and Sacramento-San Joaquin River Delta, theCentral Valley, and the Los Angeles Basinappeared to be substantial barriers to geneflow, and allele frequencies of populationsseparated by those features differedsubstantially. A partial barrier to gene flowappeared to exist along the crest of the SierraNevada. Estimated gene flow was high amongmountain lions inhabiting the Modoc Plateau,the western Sierra Nevada, and northern sectionof the eastern Sierra Nevada. SouthernCalifornia mountain lion populations mayfunction as a metapopulation; however, humandevelopments threaten to eliminate habitat andmovement corridors. While north-south geneflow along the western Sierra Nevada wasestimated to be very high, projected loss andfragmentation of foothill habitat may reducegene flow and subdivide populations. Preservation of existing movement corridorsamong regions could prevent population declinesand loss of genetic variation. This studyshows that mountain lion management andconservation efforts should be individualizedaccording to region and incorporatelandscape-level considerations to protecthabitat connectivity.

Bighorn sheep habitat use and selection near an urban environment

To further understand the impact of urban development on wildlife populations, we examined habitat use and selection by female bighorn sheep Ovis canadensis in two endangered subpopulations near a metropolitan area in southern California. One subpopulation, which had previously been found to have low reproductive success, selected urban environments while the other did not use urban areas. In the subpopulation that used urban areas, females had smaller core activity areas and selected lower elevations and gentler slopes. These females used urban sources of water but a clear relationship between levels of urban use and periods of increased water need was not evident. Diet quality was higher among females that selected urban areas, and this increase was correlated with the level of urban use. Thus, optimal foraging behavior may have contributed to the selection of urban areas. Urban use was lowest during peak months of parturition, suggesting that reproductive strategies may also have influenced temporal patterns of urban use. Although urban areas provided bighorn sheep with forage and water resources, the use of these areas may have substantial costs. For example, females using urban areas had internal parasites that were not found elsewhere in the Peninsular Ranges.

Population dynamics of bighorn sheep in the San Gabriel Mountains, California, 1967–2002

Abstract We analyzed long-term population data for bighorn sheep (Ovis canadensis nelsoni) occupying the San Gabriel Mountains in southern California. From 1967–1972 an estimated 500 bighorn sheep occupied that range. During 1968–1975 wildfires burned over half the occupied winter–spring ranges. Wildfires increased carrying capacity, and the population grew to 665 animals in 1976. During 1976–1982 adult mortality was low and recruitment was dependent on annual forage production and weather conditions during lambing. Rate of change indicated the population would double every 44 years, and it was considered to be stable. As vegetation matured and carrying capacity declined, mortality of adults and lambs increased and the population halved approximately every 8 years to 501±30 bighorn sheep in 1989. During 1989–1995 adult mortality increased and rate of change indicated the population would halve approximately every 2.8 years. From 1995–2002 the population was stable at 90 animals. Increased recruitment and an inverse relationship between number of adult ewes and recruitment rates between 1985 and 2001 suggested that neither habitat suitability nor disease was causing the dramatic population decline observed after 1989. We hypothesize that because of a declining mule deer (Odocoileus hemionus californicus) population, mountain lions (Puma concolor cougar) began to prey more frequently on bighorn sheep, which led to a dramatic decline in the sheep population after 1989.

Serosurveillance for Livestock Pathogens in Free-Ranging Mule Deer (Odocoileus hemionus)

Routine disease surveillance has been conducted for decades in mule deer (Odocoileus hemionus) in California for pathogens shared between wildlife and domestic ruminants that may have implications for the animal production industry and wildlife health. Deer sampled from 1990 to 2007 (n = 2,619) were tested for exposure to six pathogens: bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), bovine viral diarrhea virus (BVDV), Leptospira spp., Anaplasma spp. and Brucella spp. We evaluated the relationship between exposure to these pathogens and demographic risk factors to identify broad patterns in seroprevalence across a large temporal and spatial scale. The overall seroprevalence for the entire study period was 13.4% for BTV, 16.8% for EHDV, 17.1% for BVDV, 6.5% for Leptospira spp., 0.2% for Brucella spp., and 17% for Anaplasma spp. Antibodies against BTV and EHDV were most prevalent in the deer populations of southern California. Antibodies against Leptospira spp. and Anaplasma spp. were most prevalent in coastal and central northern California whereas antibodies against BVDV were most prevalent in central-eastern and northeastern California. The overall seroprevalence for Anaplasma spp. was slightly lower than detected in previous studies. North and central eastern California contains large tracts of federal land grazed by livestock; therefore, possible contact between deer and livestock could explain the high BVDV seroprevalence found in these areas. Findings from this study will help to establish baseline values for future comparisons of pathogen exposure in deer, inform on long-term trends in deer population health and provide relevant information on the distribution of diseases that are shared between wildlife and livestock.

Fire History in a Chaparral Ecosystem: Implications for Conservation of a Native Ungulate

Abstract Mature chaparral vegetation in the San Gabriel Mountains, California, resulting from long fire-return intervals (50–70 yr), has resulted in reduced visibility and availability and quality of forage, all of which are important attributes of mountain sheep (Ovis canadensis) habitat. Concomitantly, vegetation changes have decreased availability and quality of forage. We developed a resource-selection model to determine the effect of fire history on habitat use by mountain sheep, examined the hypotheses that habitat selection was associated with fire occurrence, and determined whether fire occurrence influenced the amount of potential habitat available to mountain sheep. The best model indicated that mountain sheep selected vegetation that had burned within 15 yr and avoided areas that had not burned within that time frame. We then used our model to quantify potential changes in mountain sheep habitat that have occurred over time based on fire conditions. We identified 390 km2 of mountain sheep habitat that existed in 2002 (when only 63 mountain sheep were tallied), 486 km2 in 1980 (when the mountain sheep population was at its highest), and 422 km2 in 2004 (just after a series of large wildfires). We also estimated that 615 km2 of suitable habitat would be available in a hypothetical situation in which the entire study area burned. Our results suggest that restoration of mountain sheep to their historical distribution in chaparral ecosystems will depend upon more frequent fires in areas formerly occupied by those specialized herbivores.

Mining activity and habitat use by mountain sheep (Ovis canadensis)

We studied mountain sheep in the vicinity of three high-wall limestone mines in San Bernardino County, CA, USA to evaluate factors that influenced habitat use and, specifically, to investigate the influence of mining activity on distribution of those specialized ungulates. We used aerial telemetry data to estimate a resource selection function by fitting a logistic regression model and then comparing environmental characteristics at observed sheep locations to those at random locations. Distribution of mountain sheep was most influenced by a fire in 1999 that resulted in an area they avoided. Mountain sheep used steeper slopes, areas of lower terrain roughness, higher elevations, and areas closer to escape terrain than were random points. In contrast, sheep avoided areas near roads (federal and state highways, local roads, and off-road vehicle trails) but used areas near hiking trails and a railway. Water sources had the smallest effect of the factors considered, with sheep being associated with areas further from water points than were random locations. The disturbed area associated with the mines had a moderate influence on distribution, with sheep being associated with areas closer to the mine than were random points. Mining activities can alter terrain features and vegetation structure or composition in a way that promotes occupancy by sheep if they create steep slopes and rugged terrain (escape terrain) or reduce vegetation density or height (i.e., improve visibility). Whether increased occupancy reflects a benefit depends on the demographic responses of those sheep to the resources and conditions available on mine sites; information about those responses remains lacking.

Zoonotic vector-borne bacterial pathogens in California Mountain Lions (Puma concolor), 1987-2010

Sera collected from 442 mountain lions in 48 California counties between the years of 1987 and 2010 were tested using immunofluorescence assays and agglutination tests for the presence of antibodies reactive to Yersinia pestis, Francisella tularensis, Bartonella henselae, Borrelia burgdorferi, and Anaplasma phagocytophilum antigens. Data were analyzed for spatial and temporal trends in seropositivity. Seroprevalences for B. burgdorferi (19.9%) and B. henselae (37.1%) were relatively high, with the highest exposure in the Central Coast region for B. henselae. B. henselae DNA amplified in mountain lion samples was genetically similar to human-derived Houston-1 and domestic cat-derived U4 B. henselae strains at the gltA and ftsZ loci. The statewide seroprevalences of Y. pestis (1.4%), F. tularensis (1.4%), and A. phagocytophilum (5.9%), were comparatively low. Sera from Y. pestis- and F. tularensis-seropositive mountain lions were primarily collected in the Eastern and Western Sierra Nevada, and samples reactive to Y. pestis antigen were collected exclusively from adult females. Adult age (≥ 2 years) was a risk factor for B. burgdorferi exposure. Over 70% of tested animals were killed on depredation permits, and therefore were active near areas with livestock and human residential communities. Surveillance of mountain lions for these bacterial vector-borne and zoonotic agents may be informative to public health authorities, and the data are useful for detecting enzootic and peridomestic pathogen transmission patterns, particularly in combination with molecular characterization of the infecting organisms.

Introduction: Ballot initiatives and natural resource management: Some opinions on processes, impacts, and experience

Because of their potential impacts on natural resources, Citizen Ballot Initiatives (BI) may represent the single greatest challenge natural resource managers will face while moving into a new century. We present the justification and objectives for the symposium addressing ballot initiatives and natural resource management where most articles in this issue of Human Dimensions of Wildlife were presented and discussed. Additionally, we attempt to identify potential impacts not covered in the symposium, and provide our thoughts and opinions on future direction and needs for managers facing BIs in the future.

Flawed model has serious conservation implications: Response to Turner et al.

Turner et al. (2004) developed a habitat selection model for a population of desert bighorn sheep (Ovis canadensis) in the Peninsular Ranges of southern California that is listed as a threatened and endangered population by the state of California and the federal government, respectively. We are concerned that the recent publication of an article by Turner et al. (2004) could be detrimental to the management and recovery of bighorn sheep in the Peninsular Ranges because it lends credibility to a flawed analysis of bighorn sheep habitatuse patterns. The model attempts to extrapolate conclusions from a limited subset of bighorn sheep data that is not representative of the study area and was not gathered in a manner conducive to the analysis methods used by the authors. The authors classified habitat pixels as “active” or “inactive” based on the presence-absence of bighorn sheep observations without considering monitoring intensity. Turner et al. (2004) also failed to consider the implications of basing their model almost entirely on a bighorn sheep subpopulation known to have atypical habitat selection patterns. This subpopulation in the northwestern Santa Rosa Mountains frequently used food and water sources within hillside urban areas. Because the Turner et al. (2004) model was developed using data primarily from this atypical subpopulation, the model has low external validity and is unlikely to accurately predict habitat selection by other bighorn sheep subpopulations in the Peninsular Ranges. Furthermore, with the NW sub-population used in model development now excluded from urban areas, the Turner et al. (2004) model is unlikely to accurately predict habitat selection patterns of even this sub-population. We suggest the Turner et al. (2004) model is at best only applicable to this subpopulation between the years 1994–1998.Abstract Turner et al. (2004) developed a habitat selection model for a population of desert bighorn sheep (Ovis canadensis) in the Peninsular Ranges of southern California that is listed as a threatened and endangered population by the state of California and the federal government, respectively. We are concerned that the recent publication of an article by Turner et al. (2004) could be detrimental to the management and recovery of bighorn sheep in the Peninsular Ranges because it lends credibility to a flawed analysis of bighorn sheep habitat-use patterns. The model attempts to extrapolate conclusions from a limited subset of bighorn sheep data that is not representative of the study area and was not gathered in a manner conducive to the analysis methods used by the authors. The authors classified habitat pixels as “active” or “inactive” based on the presence–absence of bighorn sheep observations without considering monitoring intensity. Turner et al. (2004) also failed to consider the implications of basing their model almost entirely on a bighorn sheep subpopulation known to have atypical habitat selection patterns. This subpopulation in the northwestern Santa Rosa Mountains frequently used food and water sources within hillside urban areas. Because the Turner et al. (2004) model was developed using data primarily from this atypical subpopulation, the model has low external validity and is unlikely to accurately predict habitat selection by other bighorn sheep subpopulations in the Peninsular Ranges. Furthermore, with the NW subpopulation used in model development now excluded from urban areas, the Turner et al. (2004) model is unlikely to accurately predict habitat selection patterns of even this subpopulation. We suggest the Turner et al. (2004) model is at best only applicable to this subpopulation between the years 1994–1998.

Comparison of trace mineral concentrations in tail hair, body hair, blood, and liver of mule deer (Odocoileus hemionus) in California

Measuring trace mineral concentrations can be an important component of assessing the health of free-ranging deer. Trace mineral concentrations in liver most accurately reflect the trace mineral status of an individual, but, in live animals, whole blood or serum are the most commonly used sample types. Trace minerals measured in serum, such as copper, zinc, and iron, do not always accurately correlate to liver concentrations, and supplementary samples for evaluating the trace mineral status in live deer would be useful. We evaluated the utility of body and tail hair for measuring selenium, copper, zinc, iron, and manganese in free-ranging mule deer (Odocoileus hemionus) by using Spearman rank correlations and linear regression. Correlations were strongest at the time of or shortly after growth of the winter coat and in resident deer. In live deer, strong correlations and moderate linear associations (R2 = 0.57) were detected between body and tail hair and whole blood selenium in December. In postmortem-sampled deer, a strong correlation and linear association (R2 = 0.80) were found between liver and body hair selenium in August–November. Results indicate that body hair, if collected during or shortly after growth of the winter coat, can be used as a supplementary sample for measuring selenium concentrations in deer. None of the other correlations and linear associations were found to be sufficiently strong to conclude that hair can reliably be utilized as a complementary sample for measuring these trace mineral concentrations.