no 



Mammals— Oia Living Resources 



For furtlier information: 



Barbara Ver Steeg 



Illinois Natural History Survey 



607 E. Peabody Dr 



Champaign, IL MS20 



Lindzey. F.G. ms2. The North American badger Pages 

 653-663 in J. A. Chapman and G.A. Feldhammer. eds. 

 Wild mammals of North America. Johns Hopkins 

 University Press, Baltimore, MD, 



Long, C.A.. and C.A, Killingley. 1983. The badgers of the 

 world. Charles C. Thomas Publishers, Springfield, IL. 

 404 pp. 



Messick, J.P, and M.G. Homocker. 1981. Ecology of the 

 badger in southwestern Idaho. Wildlife Monograph 76. 

 53 pp. 



Minta. S.C. 1990. The badger, Ta.xiilea raxas. (Caniivora: 

 Mustelidae): spatial-temporal analysis, dimorphic terri- 

 torial polygyny, population characteristics, and human 

 influences on ecology. Ph.D. thesis. University of 

 California. Davis. 317 pp. 



Moseley, E.L. 1934. Increase of badgers in northwestern 

 Ohio. Journal of Mammalogy 15; 156-158. 



Mumford, R.E. 1969. Distnbution of the mammals of 

 Indiana. Indiana Academy of Science Monograph 

 I. 114 pp. 



Mumford, RE., and J.O. Whitaker, Jr. 1982. Mammals of 

 Indiana. Indiana Universitv Press, Bloomington, IN. 

 537 pp. 



Neely, R,D.. and C.G. Hcister. compilers. 1987. The nalur- 

 al resources of Illinois: introduction and guide Illinois 

 Natural History Survey Special Publ. 6. 224 pp. 



Obbard, M.E., J.G. Jones, R. Newman. A. Booth, A.J. 

 Satterthwaite, and G. Linscombe. 1987. Furbearer har- 

 vests in North America. Pages 1007-1038 in M. Novak, 

 J. A. Baker ME. Obbard, and B. Malloch, eds. Wild 

 furbearer management and conservation in North 

 Amenca. The Ontario Trappers Association and the 

 Ministry of Natural Resources, Toronto, Ontario. 



Sargeant, A.B., and D.W. Warner 1972. Movements and 

 denning habits of a badger Journal of Mammalogy 

 53:207-210. 



Whitaker, J.O., Jr, and J.R. Gammon. 1988. Endangered 

 and threatened vertebrate animals of Indiana; their distri- 

 bution and abundance. Indiana Academy of Science 

 Monograph 5. 122 pp. 



California Sea 

 Otters 



by 



James A. Estes 



Ronald J. Jameson 



James L. Bodkin 



David R. Carlson 

 National Biological Service 



Int'ormation on the .size. dLStribution. and pm- 

 ductivity of the CalifoiTiia sea otter population 

 is broadly relevant to two federally mandated 

 goals: removing the population's listing as 

 thieatened under the Endangered Species Act 

 (ESA) and obtaining an "optimal sustainable 

 population" under the Marine Mammal 

 Protection Act. E.xcept for the population in cen- 

 tral California, sea otters (Enliydni lutris) were 

 hunted to extinction between Prince William 

 Sound. Alaska, and Baja California (Kenyon 

 1969). Wilson et al. (1991). based on variations 

 in cranial morphology, recently assigned sub- 

 specific status {E. I. nereis) to the California sea 

 otter. Furthermore, mitochondrial DNA analysis 

 has revealed genetic differences among popula- 

 tions in California. Alaska, and Asia (NBS, 

 unpublished data). 



In 1977. the California sea otter was listed as 

 threatened under the ESA, largely because of its 

 small population size and perceived risks from 

 such factors as human disturbance, compeliiion 



Sea otter (Enliydra lulns). 



with fisheries, and pollution. Because of unique 

 threats and growth characteristics, the California 

 population is treated .separately from sea otter 

 populations elsewhere in the North Pacific, 



Survey Design 



Data on the size and distribution of the 

 California sea otter population have been gath- 

 ered for more than 50 years. In 1982 we devel- 

 oped a survey technique in which individuals in 

 most of the California sea otter's range are 

 counted from shore by groups of two observers 

 using binoculars and spotting scopes. 

 Supplemental data for each sighting include 

 group size, activity, number and size of pups, 

 and habitat. Areas that cannot be counted from 

 shore are surveyed from a low-flying aircraft, 

 Rangewide surveys are done in late spring and 

 mid-autumn. 



Population Trends, 1914-93 



The California sea otter population has 

 increased steadily through most of the 1900"s 

 (Fig. I ), Rate of increase was about 5* per year 

 until the mid-1970's. Although only one survey 

 was completed between 1976 and 1982, the col- 

 lective data suggest that population growth had 

 ceased by the mid-1970"s. and that the population 

 may have declined by as much as 30% between 

 the mid-1970"s and early 1980"s. Counts made 

 since 1983 have increased at about 5%-6% per 

 year. In spring 1993. 2.239 California sea otters 

 were counted. 



The California sea otter's lineal range (dis- 

 tance along the 9-m [5-fathom] isobath between 

 the northernmost and southernmost sightings) 

 has also increased, although more slowly and 

 erratically than the population size (data sum- 

 marized by Riedman and Estes 1990). The 



