West Mojave Plan FEIR/S - Desert Managers Group

certain shrubs (e.g. winterfat) that are important in the MGS diet (Leitner and Leitner 1996)(Leitner et al. 1997).Gustafson (1993) indicated that, at that time, grazing was permitted on approximately2,106,000 acres (3,290 mi 2 ) of military and BLM lands within the known range. BLMauthorized cattle grazing on approximately 761,000 acres (1,189 mi 2 ) and sheep grazing on592,000 acres (925 mi 2 ) of potential MGS habitat (see Appendix M for a list of cattle and sheepallotments within the known range of the MGS, and a discussion of cattle grazing outside ofBLM allotments). Cattle may wander up to several miles beyond designated allotmentboundaries (see Appendix M).A total of 1,517,262 acres (2,370 mi 2 ) of BLM sheep allotments are actively being grazedwithin the known range, including 897,820 acres (1,403 mi 2 ) of public lands and 619,442 acres(968 mi 2 ) of private lands. On private lands, woolgrowers, or landowners giving thempermission, are required to obtain federal Section 10(a) permits if their activities are likely toresult in the take of tortoises. To date, there have been no such permits issued for sheep grazing.There is no discretionary action required by county or city jurisdictions for grazing on privatelands, so consequently there is no clear means of regulating this impact on private lands outsidesheep allotments.There are no region-wide data to show the incidence of sheep grazing that is notassociated with BLM allotments. However, because there exists the potential to graze in theseareas, the total sheep grazing area given above likely underestimates actual sheep grazing withinthe known range.Gustafson (1993) indicated that cattle may adversely affect the MGS by trampling andcollapsing burrows, and that sheep may compete for limited annual forage and severely tramplelocal areas. Sheep are generally grazed in the desert between late February and the middle ofJune (Gustafson 1993), which coincides with MGS emergence from hibernation (February) andthe entire activity period, particularly during very dry years when the MGS may enterhibernation in June. These are critical times for both adult and juvenile MGS to attain sufficientfat reserves to enter and successfully emerge from hibernation. The severity of impacts mayrange from marginal in lightly used areas to extreme at cattle troughs and sheep bedding areas.No consolidated data are available concerning the spatial locations of these impacts.Hybridization between Round-tailed Ground Squirrels and the MGS: Hybridizationresults when two different species interbreed to produce progeny that has genetic traits of eachspecies. Physiological, behavioral, and geographical barriers generally segregate two species.Physiological barriers, such as incompatible genitalia, different mating seasons (which alsosuggests behavioral segregation), and similar biological factors tend to remain the same, pendingevolutionary pressures. Geographical barriers may also take a long time to change (measured ingeological time frames), as is the case with the gradual disappearance of lakes that wereprevalent in the Pleistocene. However, some changes in habitat (often referred to as “typeconversion”) can occur in an instant, as when a parcel is bladed, or during several humangenerations (e.g., spread of agricultural development).Chapter 3 3-159