Age and Survivorship of the Slider (Trachemys scripta) and the Mud Turtle (Kinosternon subrubrum) in a Mississippi Farm Pond

Abstract

Freshwater turtles seem to consistently exhibit high rates of annual survivorship as adults (Iverson, 1991a), but patterns of survivorship are less consistent or less well known for juveniles. Several studies have shown that juvenile survivorship during the first several years of life was lower than in adults: Kinosternon flavescens in Iowa (Iverson, 1991b); K. subrubrum from South Carolina (Frazer et al., 1991a); and Chrysemys picta from Virginia (Mitchell, 1988), New York (Zweifel, 1989), and Michigan (Frazer et al., 1991b). Detailed data on juvenile survivorship are generally lacking for populations of other freshwater turtles. Even in the well-studied emydid Trachemys scripta, Frazer et al. (1990) reported only limited and inconclusive data for survivorship in juveniles. Iverson (1991b) has argued that at least among the kinosternids, a Type III survivorship curve best approximates the observed survivorship data, rather than the Type II curve (constant mortality) usually advocated for turtle species generally. I studied the annual survivorship of 103 juvenile T. scripta for up to 7 yr of age, obtaining high recapture rates during sampling in each of eight consecutive years. I followed longer-term survivorship of these individuals marked as juveniles by sampling again 9 yr later, and developed conclusions as to how these data address the type of survivorship curve typical of