Management of Chaparral Habitat for Mule Deer and Mountain Sheep In

Management of Chaparral Habitat for Mule Abstract: Mule deer (Odocoileus hemionus) and mountain sheep (Ovis canadensis) occur in chapar- Deer and Mountain Sheep in Southern ral habitats of the San Gabriel and San Bernar- 1 dino mountains, California. While they inhabit California similar vegetation types, differences in the physical characteristics of their habitats result in a general allopatry of these species. Manage- Vernon C. Bleich and Stephen A. Holl2 ment options applicable to deer habitat are not always practical in sheep habitat. A series of models which will assist managers with the de- sign of projects to benefit these species is presented. Options for achieving these goals are presented, and constraints with which managers must deal are detailed and discussed. There is a huge crevasse that separ- Because much of our public land is capable of ates the zoological field of wild- producing more than one product, the multiple re- life management from the botanical source management philosophy is extremely impor- field of wildlife-habitat management. tant. As human populations increase, citizens Despite the fact that each field is place more and more demands upon public lands. greatly dependent upon the other, Demands for commodities such as red meat, recrea- each marches on his own side, not tion sites, minerals, and energy increase daily. aware that they should do more than Consequently, intensive management of these re- gaze coyly at the other from a sources is becoming increasingly important. distance. Wildlife biologists must be willing to pro- F. E. Egler, 1974 vide input into all land management decisions if wildlife benefits and detriments are to be con- In southern California, vegetation most com- sidered. Until now, predictive methods for as- monly referred to as "chaparral" dominates wild- sessing the potential impacts of vegetation man- land ecosystems. Chaparral generally occurs on agement on wildlife habitat were not available. cismontane slopes, primarily between 1,200 and Multiple resource management needs an analytical 2,500 meters elevation. The species composition system which allows the prediction of the effects of chaparral is diverse, and most species are of land management activities on wildlife habi- fire-adapted (Gill 1977), or otherwise adaptable tats and, ultimately, on wildlife populations. to the application of chemical and mechanical Thomas (1979) and Salwasser and others (1980) management strategies (see Roby and Green 1976, have described the concept of a predictive wild- Green 1977a, and Leisz and Wilson 1980). life habitat-oriented system which will allow more comprehensive assessments of land manage- Until recently, land management agencies ap- ment actions on native wildlife species. The proached chaparral manipulation from a fuels system in California is known as the Wildlife management aspect. Aside from the construction Habitat Relationships Program, and is a joint of fuel breaks and occasional type conversion endeavor of many Federal and State agencies, as projects, land management was dominated by fire well as some private organizations. What fol- prevention and suppression activities. The dis- lows is being developed as an aspect of the Wild- asterous results of the 1970 fire season led life Habitat Relationships Program, and is pre- to the formulation of the Laguna-Morena Demon- sented only in an exemplary manner. stration Area in San Diego County (Newell 1979), and the concept of an active chaparral resource In southern California, two large ungulates, management program spread to other sites in mule deer (Odocoileus hemionus) and mountain southern California. sheep (Ovis canadensis), are major faunal elements of chaparral ecosystems. The objectives of this paper are to describe briefly the distri- bution and habitat requirements of these species, provide examples of various habitat management models which are being developed for the Wildlife 1 Presented at the Symposium on Dynamics and Habitat Relationships Program, and discuss options Management of Mediterranean-type Ecosystems, June and constraints in managing chaparral for wildlife. 22-26, 1981, San Diego, California. Mule deer occur throughout the mountain ranges 2 Associate Wildlife Biologist, California De- of southwestern California. Both resident and partment of Fish and Game, Hemet, Calif.; and migratory populations are present. Winter ranges Wildlife Biologist, San Bernardino National For- are generally between 400 and 2,500 meters eleva- est, U.S. Department of Agriculture, Fontana, tion, and summer ranges between 2,000 and 3,600 Calif. meters (Longhurst and others 1952). Deer inhabit Gen. Tech. Rep. PSW-58. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture; 1982. 247 diverse land forms, on slopes generally less than Table 1--Habitat capability as described by sel- 60 percent. South aspects are preferred during ected population parameters. winter, north aspects during summer (Taber and Dasmann 1958). A variety of vegetation types are Population Parameters utilized by deer (Longhurst and others 1952, Taber Habitat Recruitment and Dasmann 1958). Chamise (Adenostoma fascicu- Capability Density Mortality Emigration latum) and mixed chaparral stands commonly are used below 2,400 meters elevation (Cronemiller Increasing and Bartholomew 1950). Water generally is avail- High or stable ≥ 1 Yes able within 800 meters of occupied habitats. Moderate Stable ~ 1 No Mountain sheep occur in the San Gabriel and San Bernardino Mountains. Both resident and mi- Low Decreasing <41 No gratory populations are present (Weaver and others 1972, DeForge 1980). Winter ranges generally are between 1,200 and 2,400 meters elevation and summer ranges between 2,000 and 4,500 meters. Approx- Peek 1980), and this could be of paramount impor- imately 70 percent of the observations (Holl and tance in future sheep habitat management decisions. others 1980) showed mountain sheep used slopes from 50-90 percent, having south or southeast as- Where deer find other adjacent, unstocked but pects, and supporting vegetation dominated by high capability habitat, they may increase to chaparral whitethorn (Ceanothus leucodermis), their tolerance density and produce more disper- mountain mahogany (Cercocarpus betuloides), and sers. On deer summer ranges, this leads to rapid chamise. Mean shrub cover is approximately 30 colonization of newly available habitats, but only percent and herbaceous cover is less than 5 per- when there are sufficient high-capability ranges cent (Light and Weaver 1973). Water usually is to produce dispersers. When high capability sum- available within 400 meters of occupied habitats. mer ranges are missing, new habitats may not be readily colonized for lack of dispersers. DISCUSSION OF HABITAT MODELS On winter ranges of both species, carrying cap- acity may be exceeded because there often is no Background other suitable habitat available. Managers should attempt to balance the capacities of all seasonal While we cannot accurately predict the number ranges. High capability winter ranges are able of deer or sheep which a given vegetation type to support positive recruitment only if the sum- supports, we can predict population responses of mer ranges provide healthy animals. these species to changes in the conditions of their habitats. The models presented here pre- Perhaps the most significant implication of this dict relative changes in deer and sheep popula- concept for land management is the importance of tions with respect to the potential capabilities identifying high capability seasonal ranges and of chaparral vegetation (table 1). A high capa- either maintaining or recreating their character- bility habitat would potentially support a rela- istics. This is a distinct alternative to tively dense population, or a population of les- applying non-site-specific prescriptions to all ser density but which exhibits a high recruitment lands within a herd's seasonal range. Moderate rate. Because of environmental resistance, the capability ranges should be targeted for enhance- actual population in a high capability habitat ment. Low capability ranges should be treated may not exhibit high productivity, but this does only if they have a reasonable potential for im- not alter the habitat's (i.e., the vegetation's) provement and they are adjacent to high capability potential. A low capability habitat would not habitat. support a dense, self-sustaining population; if it contains a population, some individuals would, Within each seasonal range there are distinct by definition, be immigrants from other higher habitat elements and attributes which determine capability habitats. its capability. Selected aspects of these attributes will be addressed in the habitat models. We There are several important management impli- will focus on the following: cations in the concept of defining seasonal habi- Vegetation Stage: A designation of the existing tat capability in terms of its contribution to vegetation, its age class and canopy cover. population recruitment. Each seasonal range has Canopy Cover of Dominant Plants: Percent canopy a finite supply of forage and cover resources. If cover of plants describing the vegetation type. that supply is sufficient to support a deer popula- Stand Size: The area, in hectares, of a distinct tion, any excess individuals will disperse to other stand of vegetation. available habitats. Among sheep, the tendency to Cover and Forage Proportions:

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