Are Cross-Sectional Health Data Really Giving Us Enough Information to Characterize Populations? Enhancing Chelonian Health Through a Prospective Cohort Study
Wildlife Epidemiology Laboratory, College of Veterinary Medicine, University of Illinois, Urbana-Champaign, IL, USA
Reptile populations worldwide are at risk from multiple stressors, including habitat loss and degradation, invasive species, unsustainable use, and emerging infectious diseases.1 Chelonian health is evaluated by parameters such as hematology, pathogen presence, and clinical pathology; however, few studies exist observing these parameters within individuals over time. To address this deficit, eastern box turtles (Terrapene carolina carolina, n=22) were affixed with radiotelemetry units at a site with recurrent ranavirus mortalities. Blood samples were collected every other week from May through November 2016 and evaluated for hematologic parameters. Total white blood cell counts varied throughout the year and were observed to be higher in females, but no differences were observed based on season or average daily movement. Directly observed turtle movement did not appear to be affected by any hematologic factors, but mainly driven by environmental factors, specifically warmer temperatures and rain. Individual turtles tested positive for terrapene herpesvirus 1, box turtle Mycoplasma sp., and adenovirus, but no individual factors were significant predictors for pathogen detection. Conversely, pathogen presence was not a significant predictor for turtle health parameters when treating each turtle as nonindependent with repeated measures. Data collection over another active season should enhance ability to elucidate potential relationships among these parameters. The approach to integrate ecological and natural history factors of populations with patterns of individual health is critical to better assess population health. Furthermore, this approach can be adapted for other free-ranging and captive populations to understand temporal variation in health.
The authors would like to thank all members of the Wildlife Epidemiology Lab who contributed their time and effort in locating the turtles and with all subsequent lab work.
1. Gibbons JW, Scott DE, Ryan TJ, et al. The global decline of reptiles: déjà vu amphibians. BioScience. 2000;50(8):653–666.