West Mojave Plan FEIR/S - Desert Managers Group

TypeYearsSignCount98-99-01Distance2001Distance2002DistanceBothYearsTotal275↓56%104↓21%112↓23%216↓44%Table 3-24Characteristics of 491 Tortoises Found Between 1998 and 2002LOCATIONS OF TORTOISES 16NoObs202←74↓70%29←28%↓10%57←51%↓2086←40%↓30%Total 491 288←59%288 IN BURROWS 203 ABOVEGROUNDShrubs Open Wash Unk No Open Shrubs WashesRocksBanksObsRocks116 58 20 8 73 67 3 3←57% ←29% ←10% ←4% ←26% ←92% ←4% ←4%↓36%29 in Burrows; no location data 75←72%↓37%57 in Burrows; no location data 55←49%↓27%86 in both years 130←60%↓64%203←41%↓40%58←77%↓34%43←78%↓26%101←78%↓60%168←84%↓9%17←23%↓37%12←22%↓37%29←22%↓91%32←16%↓4%SeefootnoteOHV Impacts to Tortoises in Washes: During his studies at the Desert TortoiseNatural Area in the early 1990's, Jennings (1993, 1997a, 1997b) found that tortoisessystematically located preferred forage along the margins of small washes. They spent aconsiderable amount of time traveling along washes, and apparently used washes as navigationalaids to relocate burrows. For example, more than 25 percent of all plants on which tortoises fed,and three of the ten most-preferred plants, were in the washes and washlets, even though washescomprised only 10.3% of the study area habitats (1997). Given this information, he concludedthat OHV use may disorient tortoises (1993) and that tortoises will be forced to select other lesspreferredand possibly less-nutritious plant species (1997a).Jennings (1997a) also found that tortoises generally spent more time traveling andforaging in hills, washes, and washlets than on the flats, and that hills and washes were favoredin the planning area for use by OHV recreationists. Given this overlap, he concluded thattortoises are more likely to suffer direct mortality from vehicles than if they used the habitatrandomly.3.3.2.6.3 Direct Impacts of OHVs on Desert Tortoise HabitatHabitat Degradation: Lovich and Bainbridge (1999) found that the wheel tracks of afull-size OHV vehicle operating in an undisturbed area could damage almost 1.25 acres (0.5 ha)with every 4 miles (6.44 km) traveled. Goodlett and Goodlett (1991) reported that impacts in the16 Sign count data are shown in the 1 st row for 275 tortoises, and in the 4 th row for 216 distance-sampling tortoises86 animals found in burrows during distance sampling, but was provided for aboveground tortoises. The totalaboveground estimates of 84% in the open and 16% under shrubs are for 200 tortoises observed outside washes. Itwould be incorrect to conclude that only 3 of 203 tortoises were in washes; the correct conclusion is that 3 of 73(4%) were found in washes, in the summer to fall period; even this number is likely an underestimate, as surveyorslikely failed to indicate all tortoises and burrows associated with washes.Chapter 3 3-125