Effectiveness of Action to Reduce Exposure of Free-Ranging California Condors in Arizona and Utah to Lead from Spent Ammunition

Abstract

California condors (Gymnogyps californianus) released into the wild in Arizona ranged widely in Arizona and Utah. Previous studies have shown that the blood lead concentrations of many of the birds rise because of ingestion of spent lead ammunition. Condors were routinely recaptured and treated to reduce their lead levels as necessary but, even so, several died from lead poisoning. We used tracking data from VHF and satellite tags, together with the results of routine testing of blood lead concentrations, to estimate daily changes in blood lead level in relation to the location of each bird. The mean daily increment in blood lead concentration depended upon both the location of the bird and the time of year. Birds that spent time during the deer hunting season in two areas in which deer were shot with lead ammunition (Kaibab Plateau (Arizona) and Zion (Utah)) were especially likely to have high blood lead levels. The influence upon blood lead level of presence in a particular area declined with time elapsed since the bird was last there. We estimated the daily blood lead level for each bird and its influence upon daily mortality rate from lead poisoning. Condors with high blood lead over a protracted period were much more likely to die than birds with low blood lead or short-term elevation. We simulated the effect of ending the existing lead exposure reduction measures at Kaibab Plateau, which encourage the voluntary use of non-lead ammunition and removal of gut piles of deer and elk killed using lead ammunition. The estimated mortality rate due to lead in the absence of this program was sufficiently high that the condor population would be expected to decline rapidly. The extension of the existing lead reduction program to cover Zion (Utah), as well as the Kaibab plateau, would be expected to reduce mortality caused by lead substantially and allow the condor population to increase.

Suitability of anodic stripping voltammetry for routine analysis of venous blood from raptors

“…Moreover, most of the scarce studies available in this regard have focused on the first generation of these devices (namely, LeadCare I or simply LeadCare; Counter et al 1998;Pineau et al 2002;Zentner et al 2005;Craighead and Bedrosian 2008;Green et al 2008;Rodríguez-Ramos et al 2009;Sobin et al 2011;Langner et al 2015). However, relatively few studies have assessed their performance using analytical reference techniques in the laboratory.…”

“…These studies have focused mainly on assessing its usefulness as a tool for the rapid diagnosis of possible acute poisoning in these animals (Green et al 2008;Rodríguez-Ramos et al 2009). These studies have focused mainly on assessing its usefulness as a tool for the rapid diagnosis of possible acute poisoning in these animals (Green et al 2008;Rodríguez-Ramos et al 2009).…”

“…These studies have focused mainly on assessing its usefulness as a tool for the rapid diagnosis of possible acute poisoning in these animals (Green et al 2008;Rodríguez-Ramos et al 2009). They indicated that although there was a strong correlation between the series of values, the results obtained through the LeadCare I were underestimated up to a factor of 1.9 and that this fact obliged them to correct all the rest of the field results obtained with the LeadCare I (Green et al 2008). In that study, the authors simply performed a Spearman's correlation, indicating that the values between the 2 techniques correlated well.…”

Lead Exposure in Bald Eagles from Big Game Hunting, the Continental Implications and Successful Mitigation Efforts

“…comm.). This lack of response from condor populations is because of the large home ranges of condors, due to the temporal variation in their food sources, and the difficulties in controlling for recreational and predator hunting in field studies [27]. However, this lack of response means that more evidence is needed to convince the general public that non-lead programs can be effective in reducing deaths from lead ingestion in scavenging species such as condors and eagles.…”

Health Risks from Lead-Based Ammunition in the Environment

“…However, lead poisoning from ingestion of spent lead-based ammunition fragments continues to pose a particularly serious health threat for scavenging species. These lead-containing fragments remain the principal source of lead exposure to endangered California condors and continue to prevent the successful recovery of these birds in the wild (Church et al 2006; Finkelstein et al 2012; Green et al 2008; Parish et al 2009; Rideout et al 2012; Woods et al 2007). Other wildlife species, such as golden eagles, bald eagles, ravens, turkey vultures, and pumas, are also exposed to the fragments of spent lead ammunition (Burco et al 2012; Clark and Scheuhammer 2003; Craighead and Bedrosian 2008; Cruz-Martinez et al 2012; Fisher et al 2006; Kelly and Johnson 2011; Stauber et al 2010; Wayland and Bollinger 1999).…”