Island of misfit tortoises: waif gopher tortoise health assessment following translocation

Abstract

Translocation, the intentional movement of animals from one location to another, is a common management practice for the gopher tortoise (Gopherus polyphemus). Although the inadvertent spread of pathogens is a concern with any translocation effort, waif tortoises-individuals that have been collected illegally, injured and rehabilitated or have unknown origins-are generally excluded from translocation efforts due to heightened concerns of introducing pathogens and subsequent disease to naïve populations. However, repurposing these long-lived animals for species recovery is desirable when feasible, and introducing waif tortoises may bolster small populations facing extirpation. The objective of this study was to assess the health of waif tortoises experimentally released at an isolated preserve in Aiken County, SC, USA. Our assessments included visual examination, screening for 14 pathogens using conventional or quantitative polymerase chain reaction (qPCR) and haematological evaluation. Of the 143 individuals assessed in 2017 and 2018, most individuals (76%; n = 109 of 143) had no overt clinical evidence of disease and, when observed, clinical findings were mild. In both years, we detected two known tortoise pathogens, Mycoplasma agassizii and Mycoplasma testudineum, at a prevalence of 10.2-13.9% and 0.0-0.8%, respectively. Additionally, we found emydid Mycoplasma, a bacterium commonly found in box turtles (Terrapene spp.), in a single tortoise that showed no clinical evidence of infection. The presence of nasal discharge was an important, but imperfect, predictor of Mycoplasma spp. infection in translocated tortoises. Hemogram data were comparable with wild populations. Our study is the first comprehensive effort to assess pathogen prevalence and hemogram data of waif gopher tortoises following translocation. Although caution is warranted and pathogen screening necessary, waif tortoises may be an important resource for establishing or augmenting isolated populations when potential health risks can be managed.

Keywords: Gopherus; captivity; mycoplasma; stress; translocation; upper respiratory tract disease.

Figure 1

Model estimates of gopher tortoise probability of infection with Mycoplasma spp. based on the top model—a single parameter model that included the presence or absence of nasal discharge (A). The second-best model included the additive effects of the presence of nasal discharge and tortoise stage (B). Infection status was determined through qPCR on oral swabs collected in 2017 and 2018 from tortoises at the AGTHP (Aiken County, SC, USA). Error bars indicate SE for the model predictions.

Figure 2

Model estimates of gopher tortoise probability of infection with Mycoplasma spp. based on the additive effects of the presence of nasal discharge and scaled immature heterophils (×10³ μl⁻¹). Immature heterophils were scaled by subtracting the mean and dividing by the standard deviations. Infection status was determined through qPCR on oral swabs collected in 2017 and 2018 from tortoises at the AGTHP (Aiken County, SC). Dotted lines outside shaded grey shading indicate SE for the model predictions.