West Mojave Plan FEIR/S - Desert Managers Group

Importantly, no higher density polygons were found at the Desert Tortoise Natural Area andFremont Valley, where tortoise densities in the early 1980’s were 181-238 tortoises/mi 2 at theDTNA and 116 tortoises/mi 2 in the Fremont Valley. No higher density areas were found in theregions where Dr. Berry reported declines up to 90% on the associated study plots. Althoughtortoises certainly occur in areas north of Highway 58, it appears that many animals have diedthroughout the region since the late 1970’s, a conclusion supported by the carcass data, describedbelow.Superior-Cronese DWMA: There are seven tortoise concentration areas on about 147 mi 2 ,comprising about 15% of the 980 mi 2 Superior-Cronese DWMA, which are shown on Map 3-8.The core area occurs north of Barstow and Hinkley, east of Harper Lake, and west of IrwinRoad, in the Mud Hills-Water Valley area. Other concentrations are found in “Coyote Corner,”which is southwest of Fort Irwin, and in the Cronese Lakes area, southeast of Fort Irwin. All, ora portion of, three higher density areas comprising 17 mi 2 , are found in the Fort Irwin expansionarea. There were also 34 mi 2 of higher density areas on Fort Irwin south of the UTM 9-0 lineand adjacent areas, mostly to the northwest. The Fort Irwin expansion, then, would affect about51 mi 2 of all higher tortoise areas. No higher concentration areas were observed north of HarperLake to China Lake or in the western portions of Superior Valley. Some of these areascorrespond to recent die-off regions, where numerous recently dead tortoises have been found(see discussion below).Ord-Rodman DWMA: There are five tortoise concentration areas on about 69 mi 2 ,comprising about 18% of the 388 mi 2 Ord-Rodman DWMA, which are shown on Map 3-8.These concentration areas are included in three general regions: (1) northern portion of StoddardValley along Lenwood Wash, extending north over Daggett Ridge to near Barstow; (2) northernLucerne Valley; and (3) in the northwest corner of the DWMA, north of the Johnson ValleyOpen Area and east of Box Canyon, bordering the Twentynine Palms Marine Corps Base. TheOrd Mountains physically separate these three subregions, so that the absence of sign through themiddle part of the DWMA may be due to natural causes (i.e., fewer tortoises in elevations above4,500 feet), or may not have been surveyed. Relatively less tortoise sign was found in StoddardValley east of Highway 247, where Dr. Berry’s 1984 range map showed that concentrations wereat one time in excess of 250 tortoises/mi 2 (Map 3-7).It is noteworthy that two of the nine BLM permanent study plots occur in the Ord-Rodman DWMA, both in areas of relatively higher density sign counts. The Lucerne Valley plotis located in the northern Lucerne Valley, in the southern tortoise concentration area, and theStoddard Valley plot is located west of Daggett Ridge, in the northwestern concentration area.Dr. Berry’s studies found a 30% decline on the Lucerne Valley plot and a 5% decline on theStoddard Valley plot, which is relatively small compared to declines in excess of 75% in thenorthern and northwestern Fremont-Kramer DWMA.Pinto Mountain DWMA: There were no above-average tortoise areas in the 173 mi 2Pinto Mountain DWMA. Population densities appeared to be low, although few carcasses werefound during sign count surveys performed since 1998. There also appeared to be no older ormore recent die-off regions within this area.Chapter 3 3-88