West Mojave Plan FEIR/S - Desert Managers Group

crystals in the bladder (i.e., bladder stones; Homer et al. 1998). There is no evidence to suggestthat any of these diseases are at this time widespread, threatening population stability, orhindering population recovery.During sign count surveys in the fall and winter of 1998 through 2002, disease symptomswere observed in 7 of the 275 (2.5%) tortoises inspected. During distance sampling surveys inthe spring of 2001 and 2002 in the Fremont-Kramer and Superior-Cronese DWMAs, 6 of the 216(2.8%) tortoises inspected showed clinical evidence of disease. These very similar,independently derived results (i.e., 2.5% versus 2.8% of the tortoises observed) are summarizedin Appendix L.Evidence of URTD and possible cutaneous dyskeratosis was recorded for 13 adulttortoises. Clinical symptoms were not observed on any of the 69 subadult tortoises encountered(i.e., although the number in burrows that could not be observed has not been determined). Onecan see that all 13 of the tortoises were adults. Nine exhibited suspected signs of URTD, andfour were identified as having cutaneous dyskeratosis (see footnote). Eight males (89%) and onefemale (11%) had URTD-like symptoms, and one male (25%) and three females (75%) appearedto have cutaneous dyskeratosis.The spatial distribution for 12 of these 13 tortoises reveals that they were not clustered inany given region. Two were found south of Highway 58 in the Fremont-Kramer DWMA; fourin the Superior-Cronese DWMA; two in the Ord-Rodman DWMA; and four outside DWMAs.Seven were inside or within a mile of higher tortoise concentration areas, and five were in lowerconcentration areas 13 .Six of the 12 tortoises (50%) observed with disease-like symptoms were inside oradjacent to newer tortoise die-off regions discussed below. Two of these six tortoises areproximate to recent die-off regions in the Fremont-Kramer DWMA south of Highway 58 (i.e.,two with cutaneous dyskeratosis), and the other four (i.e., all with URTD-like symptoms) areproximate to newer die-off areas throughout the Superior-Cronese DWMAs.13 Sample sizes are too small to conclude how prevalent disease may be in the population. Nor are diseasesymptoms easily observed on all tortoises encountered, although the timing of surveys facilitates observations forclinical signs. Thus, 156 (72%) of the 216 tortoises encountered in the spring during distance sampling could beobserved, compared to only 90 (33%) of 275 animals observed during sign count surveys in the summer-fall. Themain difference appears to be the prevalence of tortoises in burrows that could not be observed in the summer-fall,compared to above-ground animals found during the spring, which were more readily observed. Even in the spring,60 animals could not be clearly observed, likely because they withdrew into their shells before the surveyor couldget a good look at them.Dr. Francesco Origgi (pers. comm., Nov 2002) has found that herpesvirus lesions in tortoises may only bevisible for about a 72-hour period, after which time the lesions disappear. Origgi’s work has shown that the animalmay be infected with no obvious clinical signs. This is also true for both clinical signs and laboratory assays (i.e.,ELISA tests) of URTD-infected tortoises. Tortoises that have clinical signs or test positive for exposure tomycoplasma on one occasion are asymptomatic and test negative on subsequent occasions. Therefore, it would bemisleading to draw conclusions about the prevalence or distribution of disease in the West Mojave population basedsolely on these dataChapter 3 3-112