Progress 06/01/94 to 06/30/04
Outputs
During the project period, we monitored the bighorn sheep population in Anza-Borrego Desert State Park (ABDSP) with the aid of telemetry collars and onsite biologists. During October 8-19, 2001, 75 bighorn sheep from 8 areas within the park were captured by net gun, sampled, and fitted with telemetry collars. These animals' movements and any mortalities are being documented, and the information will be used to determine management policies that will hopefully make the recovery of this endangered species a success. This project was funded by the California Department of Parks and Recreation.
Impacts
Peninsular bighorn sheep are currently on the Federal Endangered Species List. Data on yearly survival, birth, recruitment, and mortality rates, as well as causes of mortality and morbidity, will provide a foundation for developing management recommendations to promote the long-term survival of these animals.
Publications
- Guitierrez-Espeleta, G.A., S.T. Kalinowski, W.M. Boyce, and P.W. Hedrick. 2000. Genetic variation and population structure in desert bighorn sheep; implications for conservation. Conservation Genetics. 1:3-15
- Gutierrez-Espeleta, G.A., P.W. Hedrick, S.T. Kalinowski, and W.M. Boyce. 2001. Is the decline of desert bighorn sheep from infectious disease the result of low MHC variation? Heredity. 86:439-451.
- Ernest, H.B., E.S. Rubin, and W.M. Boyce. 2002. Fecal DNA analysis and risk assessment of mountain lion predation of bighorn sheep. Journal of Wildlife Management. 66:75-85. (in press)
- Rubin, E.S., W.M. Boyce, and E.P. Caswell-Chen. 2002. Modelling demographic processes in an endangered population of bighorn sheep. Journal of Wildlife Management. 55:000-000. (in press)
- Rubin, E.S., W.M. Boyce, C.J. Stermer, and S.G. Torres. 2002. Bighorn sheep habitat use and selection near an urban environment. Biological Conservation. (in press)
|
Progress 01/01/00 to 12/31/00
Outputs
We have continued to study the population biology and ecology of the bighorn sheep in Anza-Borrego Desert State Park (ABDSP). Some of the data collected in preceding years have been analyzed and the results published during this period.
Impacts
Peninsular bighorn sheep are currently on the Federal Endangered Species List. Data on yearly survival, birth, recruitment, and mortality rates, as well as causes of mortality and morbidity, will provide a foundation for developing management recommendations to promote the long-term survival of these animals.
Publications
- Borjesson, D.L., Christopher, M.C., and Boyce, W.M. 2000. Biochemical and hematologic reference intervals for free-ranging desert bighorn sheep. J. Wildlife Dis. 36:294-300.
- Chang, C., Chomel, B.B., Kasten, R.W., Heller, R., Kocan, K.M., Ueno, H., Yamamoto, K., Bleich, V.C., Pierce, B.M., Gonzales, B.J., Swift, P.K., Boyce, W.M., Yang, S.S., Boulouis, H., and Piemont, Y. 2000. Bartonella spp. isolated from wild and domestic ruminants in North America. Emerging Infectious Dis. 6: 306-311.
- Guitierrez-Espeleta, G.A., Kalinowski, S.T., Boyce, W.M., and Hedrick, P.W. 2000. Genetic variation and population structure in desert bighorn sheep: implications for conservation. Cons. Genetics. 1: 3-15.
- Hayes, C.L., Rubin, E.S., Jorgensen, M.C., Botta, R.A., and Boyce, W.M. 2000. Mountain lion predation on bighorn sheep in the Peninsular Ranges, California. J. Wildlife Management. 64(4): 954-959.
- Rubin, E.S., Boyce, W.M., and Bleich, V.C. 2000. Reproductive strategies of desert bighorn sheep. J. Mammalogy. 81(3): 769-786.
|
Progress 01/01/99 to 12/31/99
Outputs
This project has continued with the monitoring of bighorn sheep in Anza Borrego Desert State Park (ABDSP). Some of the data collected in preceding years have been analyzed and the results published.
Impacts
The Peninsular Bighorn Sheep are currently on the Federal Endangered Species List. Data on yearly survival, birth, recruitment, and mortality rates, as well as causes of mortality and morbidity, will provide a foundation for developing management recommendations to promote the long-term survival of these animals.
Publications
- Boyce, W.M., R.R. Ramey II, T.C. Rodwell, E.S. Rubin, and R.S. Singer. 1999. Population subdivision among desert bighorn sheep (Ovis canadensis) ewes revealed by mitochondrial DNA analysis. Molecular Ecology, 8:99-106.
- Rubin, E.S., W.M. Boyce, M.C. Jorgensen, S.G. Torres, C.L. Hayes, C.S. O'Brien, and D.A. Jessup. 1998. Distribution and abundance of bighorn sheep in the Peninsular Ranges, California. Wildlife Society Bulletin, 26(3):539-551.
|
Progress 01/01/98 to 12/31/98
Outputs
The major goal of this continuing study is to generate data that could be used to develop management recommendations that promote the long-term survival of bighorn sheep in Anza Borrego Desert State Park and the Peninsular Ranges. All radiocollared sheep have been monitored at least once per month since being collared in 1992-1993. Incidents of lion predation on radiocollared sheep were more common during the cooler, wetter winter months of the year and did not occur at the same rate in every year. One objective of the study was to document the patterns of lamb recruitment (lamb production and lamb survival) in multiple ewe groups in the Peninsular Ranges and to test hypotheses regarding factors that potentially influence the reproductive success of the individual ewe and the ewe group. Our analysis indicates that lamb production is relatively high (mean = approximately 75%) when all ewe groups and years are combined. Annual per group lamb survival to 3 and 6 months
fluctuated greatly among years and ewe groups (range 36-100% for 3-month survival and 9-80% for six-month survival). We found that the majority of lambs (approximately 75%) were born in March and April. This is a shorter lambing season than previously attributed to desert bighorn sheep. In addition, our data reveals that ewes are able to raise lambs to 6 months of age in consecutive years. We used data collected at waterhole counts during the past 26 years (1971-1996) as an index of abundance and examined this data with regression analysis to identify trends in the number of sheep observed. We found that a significant decline had occurred in Coyote Canyon during the past 26 years and that this decline was caused primarily by the cessation of bighorn sheep use of Cougar and Sheep Canyons. Carrizo Canyon, which was counted for a ten-year period (1973-1982), also exhibited a significant decline in bighorn sheep abundance during the years counted. We found; however, that bighorn sheep
abundance has remained stable in the north and south San Ysidro Mountains, regions used by two separate ewe groups. These findings provide evidence that long-term declines have occurred in the Peninsular Ranges, but that some areas have supported stable ewe groups. This suggests that ewe groups are influenced by local factors.
Impacts
(N/A)
Publications
- RUBIN, E.S., W.M. BOYCE, M. JORGENSEN S. TORRES, C. HAYES, C. OBRIEN, and D.A. JESSUP. 1998. The distribution and abundance of bighorn sheep in the Peninsular Ranges, California. Wildlife Society Bulletin. In press.
|
|