West Mojave Plan FEIR/S - Desert Managers Group

3.3.2.7 Current Effectiveness of Existing Protected AreasDesert Tortoise Research Natural Area: Although there are several ACECs in tortoisehabitat, only the DTNA was expressly established for conservation of the desert tortoise. TheDTNA has been partially fenced since the late 1970’s and completely fenced since the late1990’s. Even so, there are still threats to this most protected area. Each year a naturalist isemployed by the Desert Tortoise Preserve Committee (DTPC) to educate the public abouttortoise biology and protection. Several times each year, DTPC naturalists have encountered pettortoise owners attempting to release their animals into the DTNA (Michael Connor, pers.comm., Nov. 2002). Some of these tortoises have been symptomatic for URTD or otherdiseases. The fence line has been cut from time to time and trespass motorcycle tracks have beenseen bisecting the area within the fence (LaRue, 2001 pers. obs.). Feral dogs and ravenscontinue to be a problem.Some have questioned the efficacy of fencing off large areas, such as the DTNA, whenthe data do not appear to show that tortoise populations are increasing inside the fence. Dr.Berry (pers. comm., Nov 2002) has shown that decreases have been similar on both sides of thefence, but that tortoise numbers within the fenced area remain somewhat higher than numbersoutside the fence. Sign count and distance sampling data support Dr. Berry’s findings that therehave been significant declines in the DTNA and the surrounding region. Most importantly, theyalso show that there has been recent reproduction within the remnant population. Eight of 13(61%) tortoises found inside the fenced area were subadult animals.This may be a very significant finding, when one considers that the subadult cohort mayonly constitute 15 to 20% of the regional population. Within the 697 mi 2 area bounded byGarlock Road, Highway 14, Highway 58, and Highway 395, a total of 324 mi 2 (46%) weresurveyed. All subadults observed within the 324 mi 2 surveyed area were located within, orimmediately adjacent to, the DTNA (Map 3-9). The next nearest subadult was located 17 mileseast of the DTNA, found in the spring during line distance sampling surveys. It is promising thatthere may be recruitment in an area that has experienced significant population declines, andnoteworthy that no subadult animals were observed in any of the other older die-off regions.This may suggest that the perimeter fence is functioning in some manner to promote recruitment,and to minimize vehicle and sheep grazing impacts to reproducing females and new animals.These recruits are exceedingly vulnerable to natural predators (especially coyotes and kitfoxes), predators that have increased due to man (coyotes and ravens), vehicular cross-countrytravel, and trampling by sheep. Except for the predators, protective fencing has reduced orcompletely eliminated many of these impacts. And there is evidence that tortoise habitat isresponding in a positive way. For example, during his studies at the DTNA, comparing variousparameters inside and outside the fence, Dr. Matthew Brooks (1993) found (a) higher biomass ofnative annuals inside the fence; (b) higher biomass of non-native annuals outside the fence; (c)higher abundance of birds inside the fence; and (d) higher abundance of reptiles inside the fence.The increases, which likely show the results of habitat protection and rehabilitation, wereattributed to less human use inside the fence.Chapter 3 3-137