Crescent Lake National Wildlife Refuge

Crescent Lake National Wildlife Refuge has a history of conducting and participating in scientific research. For example, Dr. John Iverson and his students from Earlham College (Richmond, Indiana) have been capturing, measuring, individually marking, releasing, and recapturing turtles on the Refuge since 1981. 

Crescent Lake National Wildlife Refuge is home to only four turtles: the large and powerful Common Snapping Turtle (Chelydra serpentina), the colorful Western Painted Turtle (Chrysemys picta bellii), the prairie-dwelling Ornate Box Turtle (Terrapene ornata), and the odorous Yellow Mud Turtle (Kinosternon flavescens). Although the turtle diversity is not great, the numbers of each species on the Refuge are phenomenal. The changes in population and reproductive ecology of these turtles has been the subject of one of the longest running scientific field studies in the world. 

Dr. Iverson and his team have contributed greatly to our understanding of turtle biology. Some of their findings include: 

1) Some turtle species regularly live beyond 50 years of age.  

2) A female common snapping turtle once laid 97 eggs in a single nest!  

3) Western painted turtle eggs hatch in the early fall but the hatchlings remain in the nest all winter and emerge and migrate to the water in the early spring. These hatchlings commonly experience temperatures as low as 15 degrees Fahrenheit during the winter, but the hatchlings still survive without freezing. 

4) Yellow Mud Turtles are the only turtle in the world that nests while completely buried underground. 

5) Although considered a land only turtle, ornate box turtles regularly migrate to wetlands (including windmill overflows) to rehydrate. 

6) The gender of common snapping turtles, ornate box turtles, yellow mud turtles, and Western painted turtles is determined by the temperature of the underground nest during the middle third of incubation.