Source: UNIVERSITY OF CALIFORNIA, BERKELEY submitted to
GLOBAL WARMING AND SURVIVAL OF DESERT BIGHORN SHEEP
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0179300
Grant No.
(N/A)
Project No.
CA-B*-ECO-6535-H
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2001
Project End Date
Sep 30, 2004
Grant Year
(N/A)
Project Director
McCullough, D.
Recipient Organization
UNIVERSITY OF CALIFORNIA, BERKELEY
(N/A)
BERKELEY,CA 94720
Performing Department
ECOSYSTEM SCIENCES
Non Technical Summary
(N/A)
Animal Health Component
(N/A)
Research Effort Categories
Basic
30%
Applied
60%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
13508301060100%
Knowledge Area
135 - Aquatic and Terrestrial Wildlife;

Subject Of Investigation
0830 - Wild animals;

Field Of Science
1060 - Biology (whole systems);
Goals / Objectives
Our objectives are to characterize and model the current status and future prospects for survival of desert bighorn sheep in southeastern California. Bighorns exhibit a metapopulation-like distributed, inhabiting about 50 isolated mountain ranges in the California deserts. Their habitat occurs on mountaintops so global warming may cause their habitat to contract upwards with eventual extinction. We assembled a GIS model including the most important environmental variables, and on the basis of 27 previous extinctions, modeled and predicted bighorn vulnerability to climate changes projected by global climate models. Lower elevation, drier, and more isolated ranges are most vulnerable. We also used existing software (a population viability analysis model) to estimate error in our extinction in model. There may be cascading effects because the overall bighorn metapopulation is composed of smaller metapopulation clusters. Consequently, loss of certain populations effects the viability of the metapopulation cluster by loss of sources of dispersal necessary for recolonize following extinction. Although we continue to refine our data sets for the GIS model, this phase of the project is mostly complete. The next phase involves (1) using molecular genetics to establish genetic structuring of the metapopulation, (2) refine predictions of the GIS model, and (3) establishing baseline parameters on vegetation by which future changes due to climate can be monitored. Sequences of mtDNA, inherited only through the female line, will indicate the degree or mixing or isolation from dispersal of the various mountain ranges. From radio-telemetry studies, we know that males commonly move between mountain ranges in search of reproductive females. Females are much less likely to move (i. e., philopatric), but persistence of local populations in the metapopulation are dependent on dispersal of females, the reproductive unit in this species in which males do not participate in rearing of young. If females seldom reach isolated ranges, there should be a pattern in the distribution of haplotypes (mtDNA sequences) that reflects the past history of movement of females. If dispersal by females was prevalent in the past, the distribution of haplotypes should be uniform. Baseline monitoring of vegetation or other environmental variables into the future is necessary because the desert is highly stochastic. The climatic pattern is complex, being driven by two weather systems-western winter precipitation pattern and the southern summer monsoonal pattern-each largely independent in its effects. Thus, different regions of the California desert may follow different climate trends. This accounts for the very different vegetation in different parts of the desert because season, timing, and amount of precipitation have substantially different biological and ecological consequences for bighorn sheep.
Project Methods
Genetic structuring, indicating past dispersal patterns of female bighorn sheep, can be determined by the frequency distribution of mtDNA haplotypes across mountain ranges in the clusters of metapopulations. If the intervening low desert caused rare dispersal, then haplotype frequencies should show patterns based on isolation between, and exchange within mountain ranges (and metapopulation clusters). Haplotypes should be highly shared within metapopulation clusters, and not between clusters. Conversely, if movements are ubiquitous, haplotypes should be shared broadly across the entire desert. Obtaining tissue samples from bighorns-usually by tranquilizing from helicopters-is expensive and dangerous to both crew and bighorns. We are collecting fresh droppings from bighorn and extracting mtDNA from the surface. We already have successfully extracted, amplified, and sequenced mtDNA from droppings. We are beginning the DNA study with samples from isolated mountain ranges. If mountains with the lowest anticipated dispersal rate show haplotype frequencies similar to those of commonly mixing, then the entire population can be assumed to be genetically identical. Conversely, if mtDNA haplotypes show patterns, initial results will indicate the most efficient way to sample the total genetic structuring. Do they show a north-south or east-west cline? Are discontinuities between summer and winter precipitation (Mojove versus Sonoran) present and are clusters of metapopulations distinguishable? If so, past climatic patterns can be inferred, and more detailed models derived to predict effects of future climate change. If genetic structuring is found, we will use nDNA microsatellites to examine male movement as well. Measurement of fecal nitrogen content-which varies with growth and moisture content of forage plants-from the same droppings will indicate seasonal precipitation patterns. Areas with winter precipitation are expected to show winter and spring peaks in fecal nitrogen, whereas summer precipitation is expected to show summer peaks with greater variation in amount and timing. Summer thunderstorms typically result in greater precipitation where they occur, but are much more variable in time and space. We will explore measurement of stable isotopes if these larger patterns are found, because bighorn in some mountains are dependent in late summer on free water from springs, whereas in others succulent cacti, particularly barrel cactus, are consumed to obtain water at any dry season. Finally, to monitor climate changes we will try to identify plant species that shift rapidly in response to climate (i. e., elevational zones of herbaceous plants or presence-absence of acacia in the dryer areas), or shrubs that occur thorough out the California desert that show annual growth rings (trees occur in only some ranges). Ideally, the shrub time series would overlap those of pinyon pine, which occurs in some higher mountain ranges, and bristle-cone pine in the White Mountains. Then annual rings over decades from shrubs can be correlated with climatic patterns from tree-rings for hundreds (pinyon) and thousands (bristle-cone) of years.

Progress 10/01/01 to 09/30/04

Outputs
Bighorn sheep inhabit about 50 isolated mountain ranges in the California deserts. Their habitat occurs on mountaintops so global warming may cause their habitat to contract upwards with eventual extinction. Research was conducted to characterize and model the current status and predict the future prospects for survival of desert bighorn sheep in southeastern California. Droppings of bighorn sheep were collected and analyzed. Mitochondrial DNA was extracted to infer population structuring. Fecal nitrogen was analyzed to determine diet. Measurement of fecal nitrogen content-which varies with growth and moisture content of forage plants-from the same droppings will indicate seasonal precipitation patterns. Areas with winter precipitation are expected to show winter and spring peaks in fecal nitrogen, whereas summer precipitation is expected to show summer peaks with greater variation in amount and timing. Summer thunderstorms typically result in greater precipitation where they occur, but are much more variable in time and space. DNA information indicates that these populations showed a surprising degree of genetic differentiation and a large degree of spatial structuring of bighorn populations. Analyses of fecal nitrogen levels, an index of diet quality, showed that spring diet quality was significantly lower in low-elevation mountain ranges, as predicted by the climate-extinction model, and was positively correlated with lamb recruitment (and thus population growth) across ranges. Using a GIS model that includes the most important environmental variables, and data from 27 previous extinctions, we modeled the vulnerability of bighorn sheep to climate changes projected by global climate models. Lower elevation, drier, and more isolated ranges are most vulnerable. We also used existing software (a population viability analysis model) to estimate error in our extinction in model. There may be cascading effects because the overall bighorn metapopulation is composed of smaller metapopulation clusters. Consequently, loss of certain populations affects the viability of the metapopulation cluster by loss of sources of dispersal necessary for recolonize following extinction.

Impacts
The predictions from a survival model for desert bighorn sheep allows one to anticipate, and possibly mitigate, the impact of global climate warming. Data collected have established a baseline condition against which the consequences of actual future climate changes can be compared.

Publications

  • No publications reported this period


Progress 01/01/03 to 12/31/03

Outputs
We used an extinction model (Epps et al. 2004, Conservation Biology) to generate testable predictions on climate-related habitat quality and population stability. Lower mountain ranges in more southerly locations were most subject to extinction due to climate warming. To index diet quality we collected fecal samples from at least six individual desert bighorn sheep per population in 11 populations monthly during the critical winter/spring period of vegetative growth and bighorn sheep reproduction in the Mojave Desert. Preliminary analyses of fecal nitrogen levels showed that spring diet quality was significantly lower in low-elevation ranges, as predicted by the climate-extinction model. Spring diet quality is positively correlated with lamb recruitment (and thus population growth) in desert bighorn sheep. In April 2003, we collected samples from another 12 populations across a gradient of elevation and latitude to gain further statistical power for these analyses. Fecal nitrogen levels in this final set of samples are currently being analyzed. We have completed laboratory analysis of 14 microsatellite loci from fecal nuclear DNA collected in about 30 contiguous populations of desert bighorn sheep. The data contained 542 complete genotypes, from which we were able to identify 420 individual sheep using genotype-matching software. We determined the sex of all these individuals using DNA methods, and have sequenced a 680 base pair fragment of mitochondrial DNA from 340 of the 420 individuals. Results from both nuclear and mitochrondrial DNA show a large degree of spatial structuring of bighorn populations. We will use a GIS model to test how natural landscape features affect genetic similarity of adjacent populations. Our very large sample of adjacent populations will give us great statistical power for determining what features of the desert landscape serve as barriers to bighorn sheep dispersal. This in turn will allow us to model how climate-related extinction of given populations may be off-set by natural recolonization. We will also be able to test whether genetic variability has been reduced in areas under increased climate-related stress, as predicted by our extinction model.

Impacts
The predictions from our desert bighorn sheep model allows anticipation, and possible mitigation, of the impact of global climate warming. Our data establish a baseline condition against which the consequences of actual future climate changes can be compared in a biological system where the location of effects is specified.

Publications

  • Epps, C. W., McCullough, D. R., Wehausen, J. D., Bleich, V. C. and Rechel, J. L.. 2004. Effects of climate change on population persistence of desert-dwelling mountain sheep in California. Conservation Biology 18:102-113.


Progress 01/01/02 to 12/31/02

Outputs
GSY = 1 This project 1) analyzes population extinction of desert bighorn sheep in relation to spatial climatic variation to model the effects of future climatic changes, 2) compares diet quality along a transect of varying habitat quality based on climate, and 3) characterizes the genetic structure of about 25 populations predicted to be most susceptible to climate warming to assess past dispersal and re-colonization, and to test for population "bottlenecks." We used our extinction model to generate testable predictions on climate-related habitat quality and population stability in given mountain ranges by inputting predictions of climate changes from general climate change models (item 1). These results are near publication. During this period we collected fecal samples from at least six individual desert bighorn sheep per population in six populations monthly during the critical winter/spring period of vegetative growth and bighorn sheep reproduction in the Mojave Desert. In April 2002, we expanded sampling to five additional populations. Preliminary analyses of fecal nitrogen levels, an index of diet quality (item 2), showed that spring diet quality was significantly lower in low-elevation mountain ranges, as predicted by the climate-extinction model, and was positively correlated with lamb recruitment (and thus population growth) across ranges. We have begun to collect samples from 15 populations across a gradient of elevation and latitude to increase statistical power for these analyses. We sequenced DNA from feces collected from 14 populations and found significant mitochondrial haplotype variation (item 3). Populations in close proximity (separated by only a few kilometers in some cases) had entirely different haplotypes, or different haplotype frequencies. This high local genetic variation improved our estimates of female dispersal between populations. We are currently sequencing additional samples and analyzing nuclear microsatellite data at 13 loci to provide estimates of nuclear gene flow, distinguish individual big horn sheep for sequencing, and test for past population bottlenecks. In the summer of 2002 we collected feces from 10 additional populations, raising the number of populations being examined for genetic structure to about 25. This large sample of adjacent populations will give us great statistical power in determining features of the desert landscape that are barriers to dispersal. We can then model how climate-related extinction may be off-set by natural re-colonization. We presented preliminary genetic results at the Symposium of the Society for Conservation Biology in Canterbury, England, in July of 2002, as well as at the Bay Area Conservation Biology Symposium in February 2003.

Impacts
These results will allow prediction of consequences of global climate change on the distribution and abundance of desert bighorn sheep. They will guide conservation efforts in directed ways to the specific problems within the spatial structuring of the mountain ranges, and allow assessment of situations that are not sustainable, versus those where efforts should be directed to obtain the greatest good.

Publications

  • Klein, D. R., McCullough, D. R., Allen-Diaz, B., Cheville, N., Graham, R. W., Gross, J. E., MacMahon, J., Patten, D. T., Ralls, K., Turner, M. G. and Williams, E. S. 2002. Ecological dynamics on Yellowstone's northern range. National Academy Press, Washington, D. C.
  • Bowyer, R. T., McCullough, D. R., and Belovsky, G. E. 2001. Causes and consequences of sociality in mule deer. Alces 37:371-402.
  • Cypher, B. L., Koopman, M. E. and McCullough, D. R. 2001. Space use and movements by kit fox family members. Transactions of the Western Section of the Wildlife Society 37:84-87.
  • Durnin, M. E., McCullough, D. R., Huang, J. A. and Zhang, H. 2001. Estimation and characteristics of potential giant panda (Ailuropoda melanoleuca) dens in the Wolong Nature Reserve, Sichuan, China. (abstract). Thirteenth International Conference on Bear Research and Management 13:60.
  • Koopman, M. E., Cypher, B. L. and McCullough, D. R. 2001. Factors influencing space and prey use by San Joaquin kit foxes. Transactions of the Western Section of the Wildlife Society 37:77-83.
  • Beissinger, S. R. and McCullough, D. R., editors. 2002. Population Viability Analysis. University of Chicago Press.
  • Blejwas, K. M., Sacks, B. N., Jaeger, M. M. and McCullough, D. R. 2002. The effectiveness of selective removal of breeding coyotes in reducing sheep predation. Journal of Wildlife Management 66:451-462.


Progress 01/01/01 to 12/31/01

Outputs
This project examines the threat of global warming to about 50 populations of desert bighorn in the isolated mountain ranges in the deserts of southern California. A logistic regression model describing climate-related extinction was developed and final adjustments made. A manuscript was completed and submitted for publication. Droppings of bighorn sheep in 16 populations, including several recent recolonizations, were collected in the 2000 and 2001 reporting periods and mitochondrial DNA extracted to analyze population structuring. These populations showed a surprising degree of genetic differentiation, so the collections of droppings from bighorns will continue over a broad geographic area in the California deserts. These results will indicate the frequency and location of genetic exchange between populations and will be used to define metapopulations for management purposes. Information on sub-structuring and genetic diversity will be used to develop colonization models and refine extinction models. An abstract of preliminary results from this work has been accepted for presentation at the 2002 annual meeting of the Society of Conservation Biology. Pellets are also collected monthly in 6 different mountain ranges and fecal nitrogen levels measured as an indicator of dietary quality. Diet quality in populations predicted to be at high risk of extinction will be compared to populations at low risk to test a possible mechanism behind observed patterns of population persistence related to elevation and rainfall. Regional differences in seasonality due to different rainfall patterns (winter Pacific storms in the north, summer monsoon storms in the south) will also refine extinction models.

Impacts
Global climate change is one of the most important issues facing humankind, and monitoring changes in natural systems is a high priority to track changes. Bighorn sheep populations in desert ranges are particularly sensitive because they are already on the climatic cusp and have a naturally fragmented habitat distribution. Therefore they may become locally extinct rather than shifting to a more northerly distribution as climate warms. Extinction probability models allow predictions of which bighorn populations will go to extinction if the predictions of global climate change models occur. Model predictions are "hypotheses" against which actual historical changes in climate and bighorns can be tested.

Publications

  • Jennings, K. W., and McCullough, D. R. 2001. Home range analysis of urban black-tailed deer in El Cerrito and Kensington. (abstract). Annual Meeting of the Western Section of the Wildlife Society, Sacramento, California.
  • Neale, J. C. C., and Sacks, B. N. 2001. Food habits and space use of gray foxes in relation to sympatric coyotes and bobcats. Canadian Journal of Zoology 79:1794-1800.
  • Neale, J. C. C., and Sacks. B. N. 2001. Resource utilization and interspecific relations of sympatric bobcats and coyotes. Oikos 94:236-249.
  • Sacks, B. N., and Neale, J. C. C. 2001. Does paternal care of pups benefit breeding female coyotes? Great Basin Naturalist 46:121-126.
  • McCullough, D. R. 2001. Male harvest in relation to female removals in a black-tailed deer population. Journal of Wildlife Management 65:46-58.
  • McCullough, D. R. 2001. Population manipulations of North American deer Odocoileus spp.: balancing high yield with sustainability. Wildlife Biology 7:161-170.
  • McCullough, D. R. 2001. Long term decline in the deer population in Mendocino County. (abstract). Annual Meeting of the Western Section of the Wildlife Society, Sacramento, California.
  • McCullough, D. R., and McCullough. Y. 2001. Shifts in kangaroo species abundance at Yathong Nature Reserve. (abstract). 14th Annual Conference of the Australasian Wildlife Management Society, Dubbo, New South Wales, Australia.
  • Blejwas, K. M., McCullough, D. R., and Jaeger, M. M. 2001. Effects of removing breeding coyotes on coyote spatial organization (abstract). International Conference on Canid Biology and Conservation, Oxford, England.
  • Goodman, S. J., Tamate, H. B., Wilson, R., Nagata, J., Tatsuzawa, S., Swanson, G. M., Pemberton, J. M., and McCullough, D. R. 2001. Bottlenecks, drift and differentiation: a population structure and demographic history of sika deer (Cervus nippon) in the Japanese archipelago. Molecular Ecology 10:1357-1370.
  • Jaeger, M. M., Blejwas, K. M., Sacks, B. N., Neale, J. C. C., Conner, M. M., and McCullough, D. R. 2001. Targeting alphas can make coyote control more effective and socially acceptable. California Agriculture 55:32-36.


Progress 01/01/00 to 12/31/00

Outputs
More data were assembled to further refine the GIS layers and logistic regression model developed to predict the mountain ranges in the southern California deserts in which bighorn sheep are vulnerable to extinction due to global climate change. In addition, the about 50 different populations were analyzed by population viability analysis models to give Baysian probabilities of extinction to account for environmental and demographic stochasticity. Work began on collections of droppings from various mountain ranges to extract mtDNA, and first extractions were successfully made. DNA will be used to evaluate genetic structuring of the metapopulation, and estimate rates of female dispersal (mtDNA is inherited only from the mother) between mountain ranges at various distances from other populations. Although from radio-telemetry male bighorns are known to commonly cross between mountain ranges during rut, females are less likely to disperse, whereas long-term population persistence is dependent on female dispersal. From sub-samples of the same fecal samples nitrogen content will be determined as an index to diet quality to examine for consequences of timing of precipitation on bighorn nutrition, which may be more critical than total amount of precipitation. This is geographically an important question because the California deserts are influenced by two major weather systems, western storms off of the Pacific Ocean occurring in winter, and southern monsoonal storms occurring in summer. These different weather patterns appear to respond differently to global climate changes, and they have different impacts on bighorn populations in regional mountain ranges. The paleobiology literature was explored to identify possible ways of monitoring the effects of climate change over the diverse weather, vegetation, habitat, and topographic gradients found over this system of mountains.

Impacts
This research contributes to understanding of changes caused by global warming on a species of high human interest in the desert, an environment that is fragile and under-valued by society. It establishes the current conditions as baseline for future monitoring of change expected in climate patterns. Knowing the variables responsible for previous extinctions of bighorn allows identification of those mountain ranges most vulnerable to climate change. The results may reinforce the need for policies to reduce greenhouse gas emissions.

Publications

  • McCullough, D. R., Matocq, M. D., and Jones, K. 2000. Bottlenecks, founder effects, and retained genetic diversity in tule elk. (abstract) Annual Meeting of the Western Section of the Wildlife Society, Riverside, California.
  • McCullough, D. R., and McCullough, Y. 2000. Kangaroos in the Australian Outback: Behavior and ecology of three co-existing species. Columbia University Press, New York, New York.
  • Blejwas, K., Jaeger, M. M., Shin, G. T. O., and McCullough, D. R. 2000. Territoriality in a selectively exploited coyote population. (abstract) Annual Meeting of the Western Section of the Wildlife Society, Riverside, California.
  • Epps, C. W., McCullough, D. R., Wehausen, J., and Rechel, J. 2000. Climate change and the desert bighorn sheep. (abstract) Annual Meeting of the Western Section of the Wildlife Society, Riverside, California.
  • McCullough, D. R., Pei, K. C. J., and Wang, Y. 2000. Home range, activity patterns, and habitat relationships of Reeves' muntjacs in Taiwan. Journal of Wildlife Management 64:430-441.
  • McCullough, D. R. 2000. Review of The European roe deer: the biology of success, R. Andersen, P. Duncan, and J. D. C. Linnell, editors. Scandinavian University Press, Oslo, Norway. 1998. Journal of Wildlife Management 64:608-609.
  • Noss, R. F., Graham, R., McCullough, D. R., Ramsey, F. L., Seavey, J., Whitlock, C., and Williams, M. P. 2000. Review of scientific material relevant to the occurrence, ecosystem role, and tested management options for mountain goats in Olympic National Park. Report to the U.S. Department of Interior, Conservation Biology Institute, Corvallis, Oregon.


Progress 01/01/99 to 12/31/99

Outputs
Bighorn sheep inhabiting isolated desert mountains are sensitive to global climate change. About 50 populations of desert bighorn sheep (Ovis canadensis nelsoni) inhabit isolated mountain ranges in southern California, separated by a relatively hostile desert floor. Since the 1850's at least 27 local extinctions have occurred. Existing and historical population distributions were used to test whether regional climate patterns were correlated with local extinction. GIS coverage of desert bighorn populations extant or extinct in California since the 1850's was overlaid on precipitation, elevation, and geologic grids to score each bighorn range for climate, metapopulation dynamics, and other environmental factors. Logistic regression was used to assess these variables and the current status of each population (extinct or extant). Variables related to climate (elevation and precipitation) explained 42% of the variance in population persistence over the last 100 years. Populations inhabiting lower, drier mountain ranges were more likely to go extinct. Using extinction probabilities generated by the logistic regression model, native and reintroduced populations were assessed for vulnerability to climate changes. Global climate change scenarios can, thus, be evaluated for probable impacts on bighorn sheep populations. Continuing work will concentrate on identifying and measuring biological variables (e.g. woody plant growth rings) to establish baseline values to track future climate changes.

Impacts
This project identifies an important conservation issue inextricably tied to global warming, and as such, identifies an important environmental consequence of climate change that can be monitored over time.

Publications

  • Ritchie, M. E., and D. R. McCullough. 1999. Spatially structured ungulate population dynamics: causes and consequences. (abstract). Ecology and management of ungulates: integrating across spatial scales. Prestige Lakeside Resort and Conference Center, Nelson, British Columbia.
  • McCullough, D. R. 1998. Drive counts of tule elk at Point Reyes National Seashore, California. Pages 141-148 in Proceedings of the 1997 Deer/Elk Workshop, Rio Rico, Arizona, edited by J. C. deVos. Arizona. Proceedings of the Western States Deer and Elk Workshop, Rio Rico, Arizona. Arizona Game and Fish Department, Phoenix.
  • McCullough, D. R., and L. L. Severinghaus. 1998. Recovery program for the endangered Taiwan sika deer. Pages 177-184 in Advances in deer biology, edited by Z. Zomborszky. Proceeding of the 4th International Deer Biology Congress, Pannon University of Agriculture, Faculty of Animal Science, Kaposvar, Hungary.
  • McCullough, D. R. 1999. To advocate or not: values, objectivity, and professional credibility. (abstract). Annual meeting of the Western Section of the Wildlife Society, Monterey, California.
  • McCullough, D. R. 1999. To advocate or not: values, objectivity, and professional credibility. Transactions of the Western Section of the Wildlife Society 35:83-88.
  • McCullough, D. R. 1999. Density dependence and life-history strategies of ungulates. Journal of Mammalogy 80:1130-1146.
  • McCullough, D. R. 1999. Mule Deer: Odocoileus hemionus. Pages 329-331 in The Smithsonian book of North American mammals, edited by D. E. Wilson and S. Ruff, Smithsonian Institution Press, Washington, D. C.
  • Koenig, W. D., D. R. McCullough, C. E. Vaughn, J. M. H. Knops, and W. J. Carmen. 1999. Synchrony and asynchrony of acorn production at two coastal California sites. Madrono 46:20-24.
  • Sacks, B. N., M. M. Jaeger, J. C. C. Neale, and D. R. McCullough. 1999. Territoriality and breeding status of coyotes relative to sheep predation. Journal of Wildlife Management 63:593-605.