Environmental Studies Program


Date of this Version

Spring 2017


Environmental Studies Undergraduate Student Thesis, University of Nebraska–Lincoln, 2017


Copyright © 2017 Ellen Dolph


In recent years there has been a decline in herpetofauna, sparking an interest in inventory and monitoring of these declining species. Climate and drought affect population dynamics. Growth rates can be indicators of healthy individuals, populations or habitats (Moldowan et. al, 2015; Armstrong and Brooks, 2013), however, growth rates can be hard to obtain for long-lived species with individuals of unknown age, and long-term studies are rare. Mark-recapture sampling techniques can provide growth information from individuals of unknown age (Armstrong and Brooks, 2013). Though painted turtles (Chrysemys picta) are not currently a species of conservation concern and have stable populations, they are a good study species because they are common throughout the United States. The study area for this research is located at a single pond near Cedar Point Biological Station in Ogallala, Nebraska. My goal was to predict growth rates of painted turtles based on their ages through a long-term, single pond study using unknown age, mark re-capture methods. The study period included drought and non-drought periods. My objectives were to 1) fit a nonlinear growth model to my data to estimate growth rates, 2) use sex-specific models to compare growth rates of male and female painted turtle, and 3) determine impacts of climate on turtle growth rates by looking at drought years versus normal years. Turtles have been caught during the summer months for 12 years and measurements taken were used to predict turtle growth rates. Results indicated that female painted turtles have a growth rate double that of males (male k=0.1122, female k=0.2269). Drought conditions also affected growth rate, causing a decrease in growth rate (male D=-0.0226, female D=-0.0393). This has implications for scientists studying climate change impacts on wildlife if drought conditions become the new normal summer conditions.