334 



Interior Wvst — 0:ir Living Rfsaurces 



1980 desert bighorn populations were estimated 

 at 8.415-9.040 fWishart 1978). Weaver (1983) 

 conducted a state-by-state survey a few years 

 later and estimated the U.S. desert bighorn pop- 

 ulation at 1.S.980. The 1993 estimate of the pop- 

 ulation is 18,96,5-19.040 (Table). 



Table. Status and trends ot desert 

 highom sheep in the (Jnited States 

 I96()-9.V Estimate for I960hy 

 Buechner ( 1960). Esthiiates for 

 199."? from state wildhfe ageney 

 status reports presented to the 

 Desert Bighorn Council, Moab. 

 lltah, 1994. 



In California, Nelson's bighorn {Ovis canadensis nelsoni) population 

 trends are upward Peninsular bighorn {Oc cremnobates) populations are 

 lower and ate of concern 



Subspecies 



Cowan (1940) used moiphological charac- 

 ters and measurements to identify three sub- 

 species of desert bighorns (O.c. nelsoni. O.c. 

 nte.xicano. and O.c. cremnobates) occuiring in 

 the United .States. A recent reevaluation of 

 mountain sheep races in the United States, 

 however, suggested significant differences 

 between the northern and southern (desert) 

 sheep (Ramey 199.3). Differences among the 

 three desert bighorn races, however, did not 

 support separate subspecies designations. 



The distribution of desert bighorn races is 

 uncertain, although the distribution maps of 

 Trefethen ( 197.5 1 and Weaver ( 1985) are accept- 

 ed by mountain sheep biologists (Figure). 



Status and Trends by State 



Arizona 



Historically, desert bighorn occurred on all 

 mountain ranges and plateau slopes in the 

 southern, northern, and western sections of 

 Arizona (Russo 1956). In spite of early protec- 

 tion (beginning in the 1880"s). researchers 

 believed that bighorn populations declined until 

 the 1950"s (Rus'so 1956). 



Arizona began a limited hunting program in 

 1953 and reintroduction programs in 1958. The 

 Arizona Game and Fish Department conducts 

 annual helicopter surveys. Buechner (1960) 

 estimated the 1960 population at about 3,000- 

 3,500. In 1993 the population had increased to 

 an estimated 6.000 (R. Lee. Arizona Game and 

 Fish Department, unpublished data). 



California 



Desert bighorn occupied desert mountains in 

 southeast California in historical times. 



Figure. Historical range and current distribution of the 

 three subspecies of deseil bighorn in the United States 

 I redrawn from Trefethen m7.S and Weaver 1985), 



California protected bighorn in 1883, and by 

 1960 Buechner ( I960) estimated the population 

 at about 2,15(J-2,45() (1,800-2,100 O.c. nelsoni 

 and 350 O.c. cremnobates). The state began 

 transplanting in 1971 and permitted hunting 

 beginning in 1986 (Bleich et al. 1990). In 1993 

 the populations were estimated at 4,300-4,325, 

 with the breeds occupying about 50 mountain 

 ranges (S. Tones, California Department of 

 Fish and Game, unpublished data). 



The less common peninsular bighorn iO.c. 

 cremnobates) occurs in the desert mountains of 

 southeast California from Palm Springs south to 

 the Mexican border From 1977 to 1993 this 

 population declined from an estimated 1.171 to 

 400-425 indi\ iduals because of excessive lamb 

 mortality (Weaver 1989; S. Ton'es. California 

 Department of Fish and Game, unpublished 

 data). In 1992 the U.S. Fish and Wildlife 

 Service proposed listing the peninsular bighorn 

 as endangered (Toitcs et al. 1993). This sub- 

 species also occurs southward into Mexico; 

 populations there are larger. One survey esti- 

 mated a population of 780- 1. 1 70 adult bighorn 

 in northern Baja California, Mexico (DeForge 

 etal. 1993). 



Colorado 



There is no scientific evidence that desert 

 bighorn occuiTed historically in Colorado, 

 although there is habitat in the state contiguous 

 with desert bighorn habitat in Utah. Thus, desert 

 bighorn probably occurred in the state, and 

 became extirpated before subspecies" determi- 

 nations could be made. 



The Colorado Division of Wildlife began 

 transplanting desert bighorn in 1979. By 1993 

 populations containing approximately 475 

 bighorn had been established from the release 



