Bearing the burdens of these metals could shorten turtle life spans and make them less fertile, although those impacts on painted and snapping turtles have not yet been measured. They ended up comparing their results to studies of freshwater turtles in Kentucky and Iran, which enabled them to arrive at the conclusion that “Lake Michigan wetland turtles have moderate levels of heavy metal body burdens and some metals, such as copper, appear to be relatively high in these animals.” Another cause for more research on freshwater turtles, particularly regarding the way they accumulate heavy metals, is that many people eat snapping turtles.