West Mojave Plan FEIR/S - Desert Managers Group

Gustafson (1993) indicated that local populations of the MGS might disappear inresponse to prolonged drought, but that under natural conditions, it is likely that such areas canbe repopulated. He concluded, “There is no reason to believe that this pattern of extirpation andrepopulation has not occurred for thousands of years in the range of the Mohave GroundSquirrel.” What has changed, however, is pervasive and persisting human occupation of MGShabitat, particularly through the southern portion of its range from Palmdale to Lucerne Valley(WMP data). Although there are no historic records for the MGS west of Palmdale andLancaster, Gustafson (1993) indicated that it is likely that the species once occurred west ofPalmdale due to suitable plant communities (prior to their elimination for agriculture),topographies, and elevation.Trends: Brooks and Matchett (2001) provide the latest statistical summary of MGStrapping success and potential trends. They reported that there had been 1,353 individualsquirrels, found at 264 sites, between 1886 and 2000 that had been reported to the CNDDB.They concluded that trapping success had declined across most of the known range since themid-1980s, and that this decline was not associated with decreased rainfall.Their final conclusion was given as follows, “Recent attempts to locate populations fornew studies have been hampered by low trapping success, even during a period in which winterrainfall was adequate for reproduction and survival (Leitner 2000) and at sites where Mohaveground squirrels were previously abundant from the mid-1970’s through the early 1980’s. Theresults of others (Leitner 2000), coupled with the decreased trapping success since the mid-1980’s that was documented in the current study, have heightened concern that the Mohaveground squirrel may be undergoing a long-term decline in abundance.”3.3.3.2 Life History 233.3.3.2.1 Species DescriptionThe MGS is one of two members of the subgenus Xerospermophilus, which also includesthe round-tailed ground squirrel (Spermophilus tereticaudus) of the eastern Mojave and Sonorandeserts (Hall 1981; Nowak 1991). The MGS measures 8.3-9.1 inches (210-230 mm) in totallength, 2.2-2.8 inches (57-72 mm) in tail length, and 1.3-1.5 inches (32-38 mm) in hind footlength (Hall 1981), which helps differentiate it from the smaller antelope ground squirrel(Ammospermophilus leucurus) and the considerably larger California ground squirrel(Spermophilus beecheyi). Of these four species, the MGS is the only one found entirely withinthe western Mojave Desert.23 Unless otherwise noted, most of the following information is taken from the species account providedfor the West Mojave planning effort by long-time MGS trapper, David Laabs, of Biosearch Wildlife Surveys, SantaCruz, California (referenced as Laabs 1998). Many of the supporting documents were originally cited in Laabs(1998), and are herein included in the literature-cited section.Chapter 3 3-146