Assessing Lead Exposure in Free-Ranging Gray Wolves (Canis lupus) in Minnesota, USA

Abstract

The gray wolf (Canis lupus) is both an apex predator and a scavenger in Minnesota, US. Monitoring the health of Minnesota's gray wolf population is an important component of wolf management. Concern regarding whether wolves are being exposed to lead through scavenging viscera of hunter-harvested cervids left on the landscape, led to our study to determine lead-exposure rates. In fall 2012, livers from 147 hunter-harvested wolves (89 females, 58 males) were screened for lead and 20 other elements by inductively coupled plasma-atomic emission spectroscopy. Ten wolves (6.8%) were exposed to lead; only one had high enough exposure (6.14 ppm) to suggest lead toxicosis. Lead exposure varied by time of harvest, with nearly all lead-exposed wolves taken in the late hunting and trapping season (from 24 November 2012 to 31 January 2013), compared with the earlier hunting-only season (3-18 November 2012). Further, eight of 10 lead-exposed wolves were taken from deer-permit areas that harvested >1 deer/km2; only two of 10 were taken where deer harvest was less. This suggests the availability of viscera on the landscape may influence exposure risk of lead to wolves. More research is needed to determine baseline levels for toxic concentrations of lead in gray wolves and to determine clinical signs of lead poisoning in wild canids.