Excretion of three heavy metals in the shed skin of exposed corn snakes (Elaphe guttata)

Three heavy metals of regional environmental concern-lead, cadmium, and mercury-are frequently evaluated as part of wildlife bioaccumulation and health monitoring studies. Shed skins of snakes may represent a useful, nonlethal biomarker tissue for such determinations. In the present study, these three heavy metals were injected into thawed mice that were fed to corn snakes (Elaphe guttata) such that snakes received 2mg/kg of each metal/month. Shed skins were collected over a period of 34 weeks, and levels of the heavy metals were determined in skins by atomic absorption methods. Each heavy metal was readily detected in the shed skins, with mean levels as follows: lead 234 ppb, cadmium 806 ppb, and mercury 403 ppb. Control snakes that were fed nonmetal-injected mice produced shed skins that contained mean levels of 6, 12, and 20 ppb lead, cadmium, and mercury, respectively. These detection levels corresponded closely to expected trace metal contents of mouse chow and tap water. These results demonstrate that dietary metal exposure can be readily detected in shed snake skins, including at trace levels of exposure that may be consistent with, or below, environmental exposures.