Ground Ingredients: Analysis of Lead Exposure in the California Condor’s (Gymnogyps Californianus) Ground Foraging Habitat

Abstract

The California Condor (Gymnogyps californianus) is a critically endangered species that reached its nadir in 1987 with a population of 27 birds in the wild. Intensive management efforts have been implemented to aid the condors' recovery, however, anthropogenic factors, like use of lead ammunition, continue to cause fatalities in this vulnerable population. Lead toxicosis, which is responsible for approximately 40% of all condor deaths since 1992, is one of the most significant threats to condors. In birds lead poisoning leads to neurological dysfunction, reproductive impairment, immune suppression, gastrointestinal disturbance, anemia, and ultimately increased vulnerability to predation, starvation, and infection. For this research I investigate the relationship between lead exposure and condor ground foraging ecology. I analyzed a subset of data from a GPS telemetry dataset of condors in southern and central California, focusing on ground foraging locations, sites where condors are most likely to ingest lead from spent ammunition while scavenging carrion. Using these data from December 2013-2017, I explored the differences between condors with high and low blood lead concentration readings (BLC) to determine the relationships between the birds' BLCs and spatial patterns in their ground foraging. I found that the best predictor of BLC in condors was how the land that they are foraging on was managed. Non-managed lands provided the best model of BLC, indicating that policy enforcement is a major component of the issue of lead exposure in condors. My research can be used to target areas of high risk of lead exposure, where increased management efforts (lead-free food provisions, policy enforcement, and educational outreach) should be focused. Concentration (BLC) in California Condor. The graph shows the comparison between the linear (blue) and cubic (green) fits used to model BLC (as a continuous variable) using the proportion of California condor ground foraging points on non-managed lands. The cubic fit (r²=0.54) indicates a better fit than linear (r²=.32). Note that blood lead concentrations 540 and 130µg/dL were excluded as they were extreme outliers.