Population Study of Eastern Box Turtles, Terrapene carolina, at Fort Custer, Michigan
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The Eastern box turtle, Terrapene carolina, has become rare or absent in recent years from much of its former range and is considered a species of special concern in the state of Michigan. This study investigated the population of Eastern box turtles at Fort Custer to determine the status of the population and also to suggest future land management recommendations based on the findings of the study. Fort Custer is a protected area used by the Army National Guard for training. Habitat management and restoration is a concern at Fort Custer where land use has altered, and may continue to alter, the environment. Turtles were marked with numbers and multiple terrestrial habitats were surveyed. The differences between the age, plastron length, habitat distribution, and predation of male and female turtles were also examined. Very few juvenile turtles were found and most of the turtles were over the age of 25. Counting the annuli on the scutes of the turtle and estimating the wear on the shell determined age. The female sample size was 111 compared to 89 males, suggesting the presence of a slightly female biased population at Fort Custer. We also found a very high rate of predation for both sexes, but females appeared to have more signs of predation, even though more male turtles had missing limbs, which is considered a more serious injury. On average, the males had a longer plastron length than females, as would be expected. The population at Fort Custer appears as if it will decline in the future due to the fact that few juvenile turtles were found, the older age of the current population, and the presence of a high rate of predation. The inability of the population to replace itself in the future coupled with the predation by a high population of raccoons, as well as land use practices and prescribed burning could lead to a decline in the population size of box turtles at Fort Custer.