PREDATION OR DISEASE. In the wild, gopher tortoise eggs and hatchlings are preyed upon by mammals, birds, and snakes. Approximately 80–90% of nests are typically depredated, primarily by mammalian predators. It is believed that more than 90% of hatchlings may not survive their first year. Adults are not usually subject to predation, but there is evidence that they can succumb to dogs and coyotes. Gopher tortoise populations can typically withstand natural predation pressure, with only one to three of every 100 eggs probably producing a breeding adult. However, predator populations, such as raccoons and crows, can be artificially high in some habitats because of anthropogenic factors. Also, potential new tortoise predators have invaded the Southeast (nine-banded armadillo, coyote, monitor lizards, feral hogs, and red imported fire ant) via human transport or habitat alteration. Beginning in the 1990s, upper respiratory tract disease (URTD) was identified as a potential threat to the gopher tortoise, and relatively large die-offs (100–300+ shells) that might be linked to URTD were documented on several public lands in Florida. In addition to at least two Mycoplasma species responsible for URTD, gopher tortoises also may have herpesvirus and iridovirus. Pathogens may be partially responsible for recent declines in some gopher tortoise populations, but URTD may have a long evolutionary history as a gopher tortoise disease. It is possible that Mycoplasma agassizii may be detected in virtually every population, if enough tortoises are sampled. There are several possibilities why URTD has only been discovered recently: 1) increased research on the species, 2) increased stress on gopher tortoise populations from habitat fragmentation and degradation has lowered their resistance to pathogens, 3) a more virulent form of the pathogen has evolved, or (4) URTD was introduced by humans via exposure to infected captive tortoises. On Sanibel Island, 87% of tortoises tested were seropositive for exposure to the pathogen, and at least one population there appears to have experienced a 25– 50% reduction in breeding age adults. However, it has been found that many observed declines in the demographic well-being of gopher tortoise populations did not appear to be related to the presence of Mycoplasma agassizii.
PREDATION OR DISEASE. The threat from disease or predation to the PYTH has not been investigated. However, springsnails and other mollusks are known to serve as the intermediate hosts for a variety of trematodes (Xxxxxx 1987), and as prey for nonnative fish (Raisenen 1991) and crayfish (Xxxxxxxxx and Xxxxx 1996). Xxxxxx (1987) noted high incidence of trematode infestations and resulting high incidence of parasitic castration in various populations of hydrobiids in Arizona and New Mexico; PYTH was not mentioned in this study. Although nonnative fish and crayfish are widespread in aquatic systems across Arizona, we have limited information indicating their co-occurrence with PYTH. Crayfish are known to occur in the lower sample reaches of Garden Canyon and at Blacktail Canyon Spring (X. Xxxxx, 2012, pers. comm.). Fort Huachuca is implementing crayfish removal at Garden Canyon Pond and Blacktail Canyon Spring (X. Xxxxxx, 2016, pers. comm.). At this time, disease or predation does not appear to be a factor threatening the PYTH. Refer to Stressor/Conservation Measure Matrix (Appendix A) for the conservation measures and threat reduction strategy under this CCA.
