. Ptalic Ocasn Map 3-2: Current areas of desert tortoise population densities, compared to overall distributions and potential geographic range (after Berry, 1989). The BLM collects data on desert tortoise populations by employing two methods: strip transects and permanent study plots. The strip transect method consists of a pedestrian transect walked in a mile triangular configuration (.5 mile per side). All sign of tortoise within approximately 15 feet of either side of the transect is counted. Tortoise sign includes tortoises (alive or dead) burrows, scat, egg shells, tracks, and courts
. Ptalic Ocasn Map 3-2: Current areas of desert tortoise population densities, compared to overall distributions and potential geographic range (after Berry, 1989). The BLM collects data on desert tortoise populations by employing two methods: strip transects and permanent study plots. The strip transect method consists of a pedestrian transect walked in a mile triangular configuration (.5 mile per side). All sign of tortoise within approximately 15 feet of either side of the transect is counted. Tortoise sign includes tortoises (alive or dead) burrows, scat, egg shells, tracks, and courtship rings. The amount of sign per transect can be correlated with tortoise abundance by conducting transects in areas with known population levels. The relative abundance of tortoise in other areas can then be estimated by conducting tortoise transects. This technique generally indicates the relative abundance of larger tortoise and can differentiate good habitat from poor habitat (Turner et al. 1982). The number of juveniles and hatchlings in a populations are more difficult to accurately assess using transect methodology. Since 1979, more than 1,400 strip transects have been completed in Nevada, greatly increasing the scientific database related to desert tortoise distribution (NDOW 1990). The second method uses permanent study plots and a mark-recapture technique of inventory tortoise populations. Study plots are generally read every four years. Plot surveys consist of a 30 field-day capture period, followed by a 30 field-day recapture period, for a total of 60 field-days per study plot. There are 40 permanent study plots in the Mojave and Colorado Deserts: two in Utah, two in Arizona, north of the Colorado River; nine in Nevada; and 27 in California. The Coyote Springs and Sand Hollow study plots are located within the planning area in Lincoln County, Nevada. Only a limited number of the permanent study plots have multiple years of observations (NERC 1990). 3-12
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