Tracking solutions to a persistent threat: spatial movement patterns reflect lead exposure in critically endangered California condors.

Abstract

Lead contamination, an exclusively human-induced issue, poses a serious threat to the critically endangered California Condor (Gymnogyps californianus). Contamination occurs through condors' ingestion of lead ammunition residues embedded within the remains of shot animals. Detecting lead exposures typically requires resource-intensive and invasive interventions. Here, we explored a minimally invasive alternative, analyzing movement data from GPS-tagged condors in the 30-day period prior to when their blood lead levels were measured. We found spatial, but not temporal, differences in movement patterns. Lead-exposed condors traversed larger areas of the landscape, with ranges more concentrated in a previously identified high-risk zone, and shared space more extensively with one another than unexposed individuals. However, lead-exposed condors did not exhibit declining movement patterns through time when compared to unexposed birds, making movement-inferred post-exposure detection difficult. While GPS-telemetry is a useful tool in understanding condors' spatial patterns in relation to lead exposure, future research exploring how movement patterns can be used to detect, predict, and provide early warnings of at-risk condors may better inform targeted conservation efforts.