West Mojave Plan FEIR/S - Desert Managers Group

Finally, the 84% success rate was associated with areas where 87% of the high winterfat andhopsage abundance was observed; only 5 (13%) of 38 high abundance transects were foundsouth of Highway 58.One interpretation of these findings is that the MGS is somewhat more common insurveyed areas of abundant winterfat and hopsage north of Highway 58, and somewhat lesscommon in survey areas south of Highway 58. More studies are needed before firm conclusionscan be made. It is entirely possible that the MGS is less common south of Highway 58 forreasons other than lower abundances of winterfat and hopsage. For example, MGS may be lesscommon to the south due to relatively more human impacts, higher incidence of non-nativeannual species (which Dr. Leitner has suggested), or some unknown environmental factor.The 1998 survey also recorded the occurrence of saltbush, since the Leitner’s researchfound saltbush to be a recurring component in the MGS diet at the Coso study sites 27 . Fivedifferent saltbush species were observed, including Atriplex canescens, confertifolia, polycarpa,spinifera, and lentiformis. Based on these data and personal observation, saltbush was found tohave a similar pattern of occurrence as winterfat. Although the upper range for saltbush (646)was 1.5 times higher than that observed for winterfat (423), only 4 transects exceeded winterfat’supper range. Average saltbush occurrence was 3.5 to 6 times more concentrated than theaverage winterfat occurrence.Substrates for the 102 transects where MGS has been observed included 91 (89%) thatwere sandy and 11 (11%) that were rocky. For the remaining 208 transects within the knownrange, 188 (90%) were denoted as being sandy, while 20 (10%) occurred in more rocky areas.Leitner and Leitner (1989, 1990) found that sites with the highest incidence of the MGStrapped at Coso in 1988 also had the highest standing crop of annual plants. During the 1998studies (LaRue, unpublished data), as few as three and as many as 38 different species of annualplants were observed along the 102 transects surveyed at known MGS locations. Diversity ofnative species is also likely to be important to the MGS, and may be indicative of the relativelack of human disturbance in a given area. There are numerous places where OHV staging areas,sheep bedding and watering sites, and newly brushed pipeline corridors have either temporarilyor permanently eliminated both annual and perennial plants.Current Habitat Characteristics on the 19 “Aardahl-Roush Sites:” The Leitner’sCoso studies provided annually-collected data since 1989 in both low and high density MGSpopulations, and have shown consistent patterns in MGS foraging and seasonal activity relativeto rainfall. However, most trapping studies, including those of Aardahl and Roush (1985), rarelypersisted for more than three or four consecutive years (see U.S. Bureau of Land Management2000). Although the Aardahl and Roush (1985) survey was restricted to a single season, theytrapped the MGS on every one of the 22 sites they surveyed, which has rarely been repeated inrecent years. Table M-1 (Appendix M) reports their results, showing that they trapped as few as1 (DTNA site) and as many as 68 (Golden Valley) MGS at a given site. Their surveys provide27 Winterfat, hopsage, and saltbush are each members of the Chenopod family (often referred to as the “Goosefoot”family).Chapter 3 3-153