DEMOGRAPHIC CHARACTERISTICS, INCIDENCE OF RANAVIRUS INFECTION, AND SEASONAL CORTICOSTERONE LEVELS IN THE EASTERN BOX TURTLE, TERRAPENE CAROLINA CAROLINA, IN A SUBURBAN WETLANDS HABITAT OF MIDDLE TENNESSEE

Abstract

The Eastern Box Turtle, Terrapene carolina carolina, is a species of concern in Tennessee because of population decline. Decline is due mainly to anthropogenic causes including, but not limited to, road mortality, disease, and habitat fragmentation. The purpose of this study was to assess the general health of the T. c. carolina population in a suburban wetlands habitat in Murfreesboro, TN, USA (Nickajack) by measuring demographic characteristics, infection status, and physiological characteristics. Demographic characteristics recorded include population density, age class, sex ratio, and several body size measurements (e.g., carapace length and carapace height). A small blood sample (≤0.2 ml) was drawn to measure corticosterone levels, triglycerides, uric acid, innate immunity, and to determine Ranavirus infection status. The population density was estimated to be approximately 14-15.5 turtles per hectare. The age class structure had a normal distribution with most turtles falling within the middle age class (10-14 years). The sex ratio was 1.26 male:1 female. For body size, the only variable with a significant difference between males and females was straight-line carapace length in which males were longer than females. A single turtle (LPW) was positive for Ranavirus infection out of the 102 turtles sampled and tested, accounting for 1% prevalence in the sampled population. Females had higher body condition indices than males. In 2013, corticosterone levels were significantly higher in summer than in spring. In 2014, corticosterone levels were significantly higher in fall than in both spring and summer. The difference in the seasonal timing of peak corticosterone levels between the years may be related to weather conditions or associated with opportunistic mating. Corticosterone levels were positively correlated with hemolysis titer, possibly because of an immunoenhancing effect of stress hormones. In both 2013 and 2014, triglyceride levels were significantly higher in females than in males. The higher triglyceride levels of females were most likely associated with the energetic demands of egg production, carrying eggs, and nesting. Triglycerides were positively correlated with body condition, indicating greater lipid reserves in individuals with a better body condition. All other physiological measures, including total leukocytes and heterophil counts, failed to exhibit significant seasonal or sex related differences. To my knowledge, this is the first report of baseline corticosterone values and innate immunity in free-ranging T. c. carolina. The results obtained will aid in the conservation and protection of this species of concern.