| Disease is a major conservation concern for imperiled wildlife populations. While a comprehensive understanding of wildlife disease in natural systems requires cross-disciplinary insights (i.e., microbiology, veterinary medicine, epidemiology, population ecology, and behavioral ecology, among others), I focus here on ecological and epidemiological methods. Using mycoplasmal upper respiratory tract disease (URTD) in natural gopher tortoise (Gopherus polyphemus) populations as a study system, the specific objectives of this dissertation were to (1) elucidate potential long-term impacts of URTD on host population dynamics, (2) identify and quantify mechanisms driving observed stage-specific seroprevalence patterns in exposed populations, and (3) describe how movement-associated behavior can contribute to infection susceptibility at the individual-level. Specifically, through the implementation of commonly used matrix models from population ecology, I projected the potential effects of recurring mycoplasmal URTD epizootics on the long-term dynamics of gopher tortoise populations. I solely focused on the impacts of URTD-mediated mortality events, although morbidity effects can also be important in other chronic respiratory mycoplasmal infections. I determined that host demographic factors (i.e., survival, growth, and fecundity) were more important than disease-associated factors (i.e., force of infection, disease-induced mortality, outbreak duration, and outbreak frequency) on the long-term dynamics of exposed host populations, and that the largest impacts of disease were associated with the overall frequency of outbreaks and disease-induced mortality rates. Additionally, by fitting force of infection models to age-seroprevalence data, I determined that the most biologically plausible explanation for observed seroprevalence patterns involved stage-specific force of infection rates and negligible disease-induced mortality. This is consistent with other chronic respiratory mycoplasmal infections that are characterized by low mortality but high morbidity. Lastly, through the use of regression analyses and observed individual movement patterns, I attempted to quantify the risk of infection associated with individual behaviors. Movement-associated behavior, along with sex and site classification, was found to be significantly associated with individual infection status; however, this association was most likely a retro-causal one, whereby infected tortoises were more likely to exhibit foraging and basking behavior than mate-seeking behavior. Overall, the three studies comprising this dissertation provided insights into the epizootiology of mycoplasmal URTD in natural gopher tortoise populations, and its potential impacts on long-term host population dynamics. |
