John D. Wehausen

Effects of capture on biological parameters in free-ranging bighorn sheep (Ovis canadensis): evaluation of normal, stressed and mortality outcomes and documentation of postcapture survival.

Blood samples and physiological data were collected from 634 bighorn sheep (Ovis canadensis) captured by four different methods between 1980 and 1986 in the western United States. These parameters were evaluated for selected physiological, biochemical and hematological values. Postcapture biological parameters were compared among bighorn sheep according to four different outcomes; normal, stressed or compromised, capture myopathy (CM) mortality, and accidental mortality. Significant differences (P < 0.05) were noted between outcome groups relative to certain parameters: temperature, respiration, creatinine phosphokinase (CPK), lactic dehydrogenase (LDH), serum glutamic oxaloacetic transaminase (SGOT), blood urea nitrogen (BUN), glucose, white blood cell count (WBC) and plasma pH. Such differences between groups may help in evaluating the clinical status of bighorn sheep at capture, enabling one to predict those animals that might develop CM at a later date, indicate candidates for preventive medical treatment prior to release, and/or which should be followed closely to determine long-term survival. Evaluation of follow-up data (n = 77) related to outcome status and long-term survival of bighorn sheep indicated that <4% (3 of 77) were dead within 1 mo of capture (one of these had been classified as normal and two as stressed or compromised at capture); <3% (3 of 77) were dead >1 mo, and <6 mo after capture two were classified in the stressed outcome and one as diseased. Eighty-eight percent (68 of 77) were alive from 1 mo to 5 yr after capture (53 were classified as normal, 12 as stressed or compromised and 3 as diseased), and 2% (1 of 77) had chronic CM but was still alive (this animal had been classified as normal). Of 77 sheep in the follow-up group, <3% (2 of 77) were not observed following capture (one was classified as normal and one as stressed and diseased). Of the fatalities, <3% (2 of 40) had been captured by the net-gun and <4% (1 of 27) by drive-net. Those two unobserved in the follow-up group also had been caught with the net-gun, 5% (2 of 40). The single surviving CM case had been captured by the net-gun. Although the net-gun appears to be one of the safest methods of capturing individual bighorn sheep, based on evaluation of capture data and biological parameters, it may not be associated with the best long-term survival in some bighorn sheep. This further emphasizes the need for close monitoring of animals at capture and following their release.

Migratory patterns of mountain lions : Implications for social regulation and conservation

We studied movements of mountain lions ( Puma concolor ) in the southern Sierra Nevada of California from 1992–1997. We observed two distinct patterns, which likely represent strategies of mountain lions for coping with variability in abundance of their primary prey, mule deer ( Odocoileus hemionus ). Some mountain lions migrated together, often slowly, following movements of mule deer from winter range toward the summer range of their prey. Those mountain lions remained together on the eastern scarp of the Sierra Nevada and overlapped in distribution throughout the year. Other mountain lions exhibited rapid movements to disjunct summer ranges, on the western side of the Sierra Nevada, shared with mountain lions that did not occur on their winter range. Mountain lions that moved more slowly and overlapped in distribution had large annual home ranges (95% adaptive kernel; X = 817 km2), whereas mountain lions with distinct summer ( X = 425 km2) and winter ( X = 476 km2) distributions had smaller home ranges. Such disparate patterns of movement may lead to difficulties in sampling population size for mountains lions. Moreover, maintaining corridors that would allow for both patterns of movement may be critical for the conservation of these large felids. Finally, extensive overlap in the distribution of mountain lions, especially the association of one group of individuals on winter range and another on summer range for mountain lions with disjunct distributions, indicates a more flexible social system than previously described.

Population-specific vital rate contributions influence management of an endangered ungulate.

To develop effective management strategies for the recovery of threatened and endangered species, it is critical to identify those vital rates (survival and reproductive parameters) responsible for poor population performance and those whose increase will most efficiently change a populations trajectory. In actual application, however, approaches identifying key vital rates are often limited by inadequate demographic data, by unrealistic assumptions of asymptotic population dynamics, and of equal, infinitesimal changes in mean vital rates. We evaluated the consequences of these limitations in an analysis of vital rates most important in the dynamics of federally endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae). Based on data collected from 1980 to 2007, we estimated vital rates in three isolated populations, accounting for sampling error, variance, and covariance. We used analytical sensitivity analysis, life-stage simulation analysis, and a novel non-asymptotic simulation approach to (1) identify vital rates that should be targeted for subspecies recovery; (2) assess vital rate patterns of endangered bighorn sheep relative to other ungulate populations; (3) evaluate the performance of asymptotic vs. non-asymptotic models for meeting short-term management objectives; and (4) simulate management scenarios for boosting bighorn sheep population growth rates. We found wide spatial and temporal variation in bighorn sheep vital rates, causing rates to vary in their importance to different populations. As a result, Sierra Nevada bighorn sheep exhibited population-specific dynamics that did not follow theoretical expectations or those observed in other ungulates. Our study suggests that vital rate inferences from large, increasing, or healthy populations may not be applicable to those that are small, declining, or endangered. We also found that, while asymptotic approaches were generally applicable to bighorn sheep conservation planning; our non-asymptotic population models yielded unexpected results of importance to managers. Finally, extreme differences in the dynamics of individual bighorn sheep populations imply that effective management strategies for endangered species recovery may often need to be population-specific.

Recruitment Dynamics in a Southern California Mountain Sheep Population

Lamb: ewe ratio data spanning the years 1953-82 for mountain sheep (Ovis canadensis) in the Santa Rosa Mountains of southern California were analyzed by multiple regression to investigate hypothesized controlling factors. Precipitation during November, January, and February as independent variables each showed a significant positive influence on recruitment rate, in accord with expectations for this desert environment. Between 1962 and 1976, an unidentified 4th factor (probably rising population density) caused a slow decline in recruitment ratio. This ratio plummeted in 1977 and averaged about 25% of the ratio predicted from precipitation alone for 1977-82, a period coincident with a suspected disease epizootic. A similar period of depressed lamb recruitment was found for the 1953-61 period, suggesting the possibility of a recurrent phenomenon. Data needs and various hypotheses concerning factors potentially underlying the observed and future population dynamics are discussed. J. WILDL. MANAGE. 51(1):86-98 Multiple factors potentially underlie the dynamics of wild ungulate populations. The partitioning of the relative magnitude of the influence of different factors in different species and ecological settings is one of the primary objectives of research related to wildlife management. This understanding is crucial if management activities are to be focussed on factors whose manipulation will produce a population response (Leopold 1933). California currently has mountain sheep populations in approximately 50 mountain ranges, mostly in desert regions (Weaver 1975, 1982). Adequate data existing for a small number of these populations indicate recent dynamics varying from rapid population increases to disappearance (DeForge et al. 1981; Weaver 1982; Bleich 1983; Holl and Bleich 1983; Wehausen 1983a,b). Weaver (1975) considered the mountain sheep population of the Santa Rosa Mountains to be one of the 2 largest populations in California. Recently it has come to the forefront as a major population suggested to be declining rapidly due to excessive lamb mortality that began in 1977 (DeForge and Scott 1982). Blood samples from mountain sheep in this range have yielded titers to 4 viral diseases: parainfluenza-3 (PI-3), bluetongue (BT), epizootic hemorrhagic disease (EHD), and contagious ecthyma (CE) (DeForge et al. 1982; Turner and Payson 1982a,b). PI-3 and BT have been suggested as factors predisposing lambs to fatal bacterial pneumonia. This paper attempts to quantify the influence of the purported disease epizootic and other variables on lamb recruitment through statistical analyses of lamb:ewe ratio data spanning 30 years. In addition to the expected depressing effects of diseases on lamb recruitment, it was hypothesized that precipitation and population density also should influence recruitment rate through their influence on nutrition. The Santa Rosa Mountains are a desert ecosystem of low and variable precipitation (Ryan 1968). Consequently, variance in precipitation was expected to strongly affect nutrition and survival of lambs through its influence on vegetative growth (Monson 1960). Work in the nearby Mojave Desert has indicated that the timing of precipitation is of particular importance to subsequent plant growth (Beatley 1974). Specifically, fall precipitation is a crucial determinant of whether annual and perennial forb growth will be present the following spring and strongly influences spring growth of shrubs and perennial grass species. Winter and early spring precipitation also can trigger growth in shrubs and perennial grasses. Turner (1973) found that mountain sheep in the Santa Rosa Mountains consumed a mixture of browse, forb, grass, and cactus species that varied seasonally and yearly with availability of succulent growth. Particularly noteworthy relative to nutrition of lambs was an increase in consumption of forbs and green grasses during spring in years when these were available.

Elevation and connectivity define genetic refugia for mountain sheep as climate warms

Global warming is predicted to affect the evolutionary potential of natural populations. We assessed genetic diversity of 25 populations of desert bighorn sheep (Ovis canadensis nelsoni) in southeastern California, where temperatures have increased and precipitation has decreased during the 20th century. Populations in low‐elevation habitats had lower genetic diversity, presumably reflecting more fluctuations in population sizes and founder effects. Higher‐elevation habitats acted as reservoirs of genetic diversity. However, genetic diversity was also affected by population connectivity, which has been disrupted by human development. Restoring population connectivity may be necessary to buffer the effects of climate change on this desert‐adapted ungulate.

Genetic relatedness of the Preble's meadow jumping mouse (Zapus hudsonius preblei) to nearby subspecies of Z. hudsonius as inferred from variation in cranial morphology, mitochondrial DNA and microsatellite DNA: implications for taxonomy and conservation

The Preble’s meadow jumping mouse (Zapus hudsonius preblei) is listed as a threatened subspecies under the United States Endangered Species Act (US-ESA). The quantitative description of this subspecies was based on cranial measurements of only three adult specimens. It is one of twelve subspecies of Z. hudsonius and is a peripheral population at the western edge of its range. We tested the uniqueness of Z. h. preblei relative to other nearby subspecies of Z. hudsonius using a hypothesis testing approach and analyses of cranial morphometric, mtDNA sequence and nuclear microsatellite data obtained from museum specimens and archived tissues. Morphometric analysis of variance did not support the original description of Z. h. preblei as a subspecies. Principal component analysis of these data showed Z. h. preblei within the range of variation found in Z. h. campestris and Z. h. intermedius. Discriminant analysis correctly classified only 42% of Z. h. preblei skulls at jackknifed posterior probabilities >0.95 relative to Z. h. campestris. All mtDNA haplotypes found in Z. h. preblei were also found in Z. h. campestris. Simulation based estimates of current and historical gene flow (MDIV) revealed low, but non-zero, mtDNA gene flow among Z. h. preblei and several nearby subspecies. Analyses of five nuclear microsatellite loci using population pairwise FST, BAPS and STRUCTURE were consistent with morphometric and mtDNA results. These revealed low levels of genetic structure and evidence of recent gene flow and bottlenecks inZ.h.preblei. Due to a lack of clearly recognisable genetic, morphological, or adaptive differences, we synonymise Z. h. preblei and Z. h. intermedius with Z. h. campestris. We suggest that candidates for listing under the US-ESA, or similar biodiversity laws, be evaluated for genetic and/or morphological uniqueness to prevent the misallocation of resources to non-distinct taxa like Z. h. preblei.

Timing of Feeding Bouts of Mountain Lions

Onset of feeding by mountain lions ( Puma concolor ) on individual prey was studied with an automatic camera near mule deer ( Odocoileus hemionus ) that had been killed and cached by mountain lions. We categorized mountain lions as adult males, adult females, females with juveniles, and females with kittens. After sunset, females with kittens returned to kills significantly earlier than males, females, or females with juveniles. Early feeding by females with kittens might reflect avoidance of conspecifics, which are known to kill kittens. Alternatively, mothers with young kittens may remain closer to caches of prey than lone males, females, or mothers with juveniles. Increased energetic needs of lactating mothers also may dictate earlier feeding.

CRANIAL MORPHOMETRIC AND EVOLUTIONARY RELATIONSHIPS IN THE NORTHERN RANGE OF OVIS CANADENSIS

Abstract Univariate and multivariate statistical methods were used to examine geographic variation in skull and horn characters of 694 bighorn sheep (Ovis canadensis) specimens from the Great Basin north to British Columbia and Alberta to test previous taxonomic hypotheses. Substantially more morphometric variation in skull and horn size and shape was found west of the Rocky Mountains than within the Rocky Mountains. Our results did not support the recognition of Audubons bighorn sheep (O. c. auduboni) as a subspecies separate from Rocky Mountain bighorn sheep (O. c. canadensis). California bighorn sheep (O. c. californiana) from Washington and British Columbia were not distinguishable from Rocky Mountain bighorn sheep but differed notably from populations in the Sierra Nevada considered part of that subspecies. Extirpated native populations from northeastern California, Oregon, and southwestern Idaho, also considered to be O. c. californiana, shared with Nelson bighorn sheep (O. c. nelsoni) from the Great Basin desert a horn-related character that distinguished them from Rocky Mountain bighorn sheep. Bighorn sheep from the Sierra Nevada were found to be distinguishable from those of the adjacent Great Basin region. Our morphometric results were concordant in geographic patterns with mtDNA data. We synonymize O. c. auduboni with O. c. canadensis. We also assign extant and extinct native populations of O. c. californiana from British Columbia and Washington to O. c. canadensis. Finally, we assign the extinct native populations of O. c. californiana from Oregon, southwestern Idaho, northern Nevada, and northeastern California to the Great Basin Desert form of O. c. nelsoni, recognizing that some transition to Rocky Mountain bighorn sheep probably occurred along that northern boundary. With these taxonomic revisions, the range of O. c. californiana includes only the central and southern Sierra Nevada.

Fecal Measures of Diet Quality in Wild and Domestic Ruminants

Fecal indices of diet quality are often used to assess diet quality in free-ranging ungulates, but the nutritional attribute fecal indices measure, the mechanism by which it is measured, and the assumptions involved are seldom considered. I developed an algebraic model relating apparent digestibility (DIG) of diets to endogenous and dietary sources of fecal components. This model predicted that if the ratio of metabolic fecal products to dry matter intake (MFP: DMI) is constant, and a fecal measure indexes MFP, then (1) the fecal index will measure DIG, (2) the relationship between DIG and the fecal index will be curvilinear and asymptotic, and (3) other nutritional characteristics of the diet will be indexed only to the extent that they are correlated with DIG. I used published data from domestic sheep and cattle to test the model assumption that MFP: DMI was constant and to test model predictions for percent fecal nitrogen (FN). Variation in MFP: DMI was partitioned into random variation and that related to apparent indigestibility (INDIG; r 2 = 0.46, P < 0.001). Variation in MFP: DMI related to INDIG slightly altered the expected curvature of the relationship between DIG and fecal measures, whereas remaining random variation influenced the resolution of that relationship. Domestic sheep and cattle on grass diets had the predicted curvilinear relationship between DIG and FN. Also, curvilinear relationships between DIG and FN were similar between domestic sheep fed grass and alfalfa diets, despite different (P < 0.001) intercepts. In contrast, slopes of the relationships between dietary N and FN for domestic sheep differed (P < 0.001) between grass and alfalfa diets, with little overlap between the 2 forage groups, supporting the prediction that dietary N is not indexed directly by FN. Reduced protein digestibility from dietary tannins will confound the relationship between DIG and FN because increased forage N in FN reduces the ability of FN to index MFP. Other potential fecal indices may be less influenced by tannins. I recommend using a natural log transformation of fecal measures that index MFP to linearize their relationship with DIG. The model provides a conceptual framework for additional research relative to fecal measures of diet quality.

Translating Effects of Inbreeding Depression on Component Vital Rates to Overall Population Growth in Endangered Bighorn Sheep

Evidence of inbreeding depression is commonly detected from the fitness traits of animals, yet its effects on population growth rates of endangered species are rarely assessed. We examined whether inbreeding depression was affecting Sierra Nevada bighorn sheep (Ovis canadensis sierrae), a subspecies listed as endangered under the U.S. Endangered Species Act. Our objectives were to characterize genetic variation in this subspecies; test whether inbreeding depression affects bighorn sheep vital rates (adult survival and female fecundity); evaluate whether inbreeding depression may limit subspecies recovery; and examine the potential for genetic management to increase population growth rates. Genetic variation in 4 populations of Sierra Nevada bighorn sheep was among the lowest reported for any wild bighorn sheep population, and our results suggest that inbreeding depression has reduced adult female fecundity. Despite this population sizes and growth rates predicted from matrix-based projection models demonstrated that inbreeding depression would not substantially inhibit the recovery of Sierra Nevada bighorn sheep populations in the next approximately 8 bighorn sheep generations (48 years). Furthermore, simulations of genetic rescue within the subspecies did not suggest that such activities would appreciably increase population sizes or growth rates during the period we modeled (10 bighorn sheep generations, 60 years). Only simulations that augmented the Mono Basin population with genetic variation from other subspecies, which is not currently a management option, predicted significant increases in population size. Although we recommend that recovery activities should minimize future losses of genetic variation, genetic effects within these endangered populations-either negative (inbreeding depression) or positive (within subspecies genetic rescue)-appear unlikely to dramatically compromise or stimulate short-term conservation efforts. The distinction between detecting the effects of inbreeding depression on a component vital rate (e.g., fecundity) and the effects of inbreeding depression on population growth underscores the importance of quantifying inbreeding costs relative to population dynamics to effectively manage endangered populations.