West Mojave Plan FEIR/S - Desert Managers Group

Overall, one sees that 68% of the 391 mi 2 within these eight wilderness areas are below20% slope, and therefore relatively more suitable tortoise habitat, in terms of this one factor.Grass Valley (94%), Black Mountain (79%), Cleghorn Lakes (71%), and Sheephole Valley(70%) are the wilderness areas that are predominantly below 20% slope. Newberry Mountain(58%), Golden Valley (46%), and Rodman Mountains (37%) rank as the three wilderness areaswith relatively more area above 20% slope.The 4,000-foot cut-off is another measure used in Table 3-28. The 3,362 transects weresurveyed in an area 20 of 3,378 mi 2 . There were 70 mi 2 surveyed above 4,000 feet and 3,308 mi 2surveyed below 4,000 feet. Only one tortoise was observed above 4,000 feet, with the remaining260 found below. When one factors in the area of survey, there were 0.014 tortoises/mi 2(tortoises were observed in 1.4% of the survey area), compared to 0.078 tortoises/mi 2 (observedin 7.8% of the survey area). In general, then, tortoises were about 6 times more likely to beobserved below 4,000 feet than above. As with 20% slope, most (89%) of wilderness areasoccurs below 4,000 feet elevation, and are therefore relatively more suitable.Given these observations, which suggest that wilderness areas are mostly below 20%slope (68%) and mostly below 4,000 feet elevation (89%), the next comparisons consider thedata that were collected in these areas. The relative survey effort within each of the eightwilderness areas in the tortoise range where 141 sign count transects were surveyed between1998 and 2002 are compared in the following table. Table 3-29 lists the number of transectssurveyed, the area covered by the survey, and percent of the area surveyed within each of theeight wilderness areas.Table 3-29Sign Count Survey Effort within Each of theEight Wilderness Areas in the Tortoise RangeWILDERNESS AREA NO. TRANSECTS NO. MI 2 SURVEYED % OF AREA SURVEYEDSURVEYEDBlack Mountain 21 Transects 13 mi 2 39% of 33 mi 2Cleghorn Lakes 12 12 19% of 62 mi 2El Paso Mountains 10 4 10% of 38 mi 2Golden Valley 14 6 10% of 57 mi 2Grass Valley 35 30 59% of 51 mi 2Newberry Mountains 15 10 23% of 43 mi 2Rodman Mountains 29 24 44% of 54 mi 2Sheephole Valley 5 2 4% of 53 mi 2Totals 141 Transects 101 mi 2 26% of 391 mi 2One can see that about 26% (i.e., 101 of 391 mi 2 ) of the eight wilderness areas wassurveyed, ranging from a low of 4% in Sheephole Valley up to 59% in Grass Valley. BlackMountain (39%) and Rodman Mountains (44%) were also fairly well covered compared to many20As in previous discussions, there is a slight discrepancy between the numbers of transects and the area surveyed.Both numbers are derived from GIS coverages, however the area surveyed is often smaller than the number oftransects surveyed. Thus, in the table that follows, there were 141 transects covering only 101 mi 2 , because only thearea within a given square mile surveyed that occurs within wilderness is reported. These numbers should beconsidered as a rough index, and not necessarily characteristic of the entire area being described.Chapter 3 3-139