Lead Exposure And Hormonal Stress Response In California Condors

The primary factor inhibiting the recovery of the critically endangered California condor (Gymnogyps californianus) is lead poisoning from ingestion of spent lead ammunition. My dissertation research documents the sources and effects of lead poisoning in condors, and provides the first information on the effects of lead on the hormonal stress response in condors. My first chapter aims to help identify sources of lead to condors by investigating three illegal condor shooting events. I use lead isotope ratios of condor tissues as well as ingested and embedded ammunition to find probable cause to link these shooting events. For my second and third chapters, I provide what are to the best of my knowledge the first data on the hormonal stress response in condors, and how lead exposure impacts this stress response. We know the vast majority of wild California condors are frequently lead poisoned, but we have limited data on how these frequent lead poisoning events affect the birds’ physiology. Lead poisoning has been shown in other organisms to heighten the hormonal stress response, which can lead to suppressed fitness in wild birds. My findings indicate that this dysfunction is occurring in wild condors, as I found a positive association between hormonal stress response outcomes and the amount of time a condor spends at risk for lead poisoning (foraging outside the management area). Interestingly, I also found that the annual frequency of a condor feeding on marine mammals, which contain high levels of hormone-disrupting chemicals such as polychlorinated biphenyls, is also associated with hormonal stress response elevation. My work fills a critical lack in our understanding of how long-term contaminant exposure might impact the California condor recovery effort, and has important implications for other scavenging species exposed to lead and other environmental contaminants worldwide. Future study is needed to investigate whether the altered hormonal stress response is impairing the fitness, survival and reproduction of wild condors

Lead Exposure And Hormonal Stress Response In California Condors

The primary factor inhibiting the recovery of the critically endangered California condor (Gymnogyps californianus) is lead poisoning from ingestion of spent lead ammunition. My dissertation research documents the sources and effects of lead poisoning in condors, and provides the first information on the effects of lead on the hormonal stress response in condors. My first chapter aims to help identify sources of lead to condors by investigating three illegal condor shooting events. I use lead isotope ratios of condor tissues as well as ingested and embedded ammunition to find probable cause to link these shooting events. For my second and third chapters, I provide what are to the best of my knowledge the first data on the hormonal stress response in condors, and how lead exposure impacts this stress response. We know the vast majority of wild California condors are frequently lead poisoned, but we have limited data on how these frequent lead poisoning events affect the birds’ physiology. Lead poisoning has been shown in other organisms to heighten the hormonal stress response, which can lead to suppressed fitness in wild birds. My findings indicate that this dysfunction is occurring in wild condors, as I found a positive association between hormonal stress response outcomes and the amount of time a condor spends at risk for lead poisoning (foraging outside the management area). Interestingly, I also found that the annual frequency of a condor feeding on marine mammals, which contain high levels of hormone-disrupting chemicals such as polychlorinated biphenyls, is also associated with hormonal stress response elevation. My work fills a critical lack in our understanding of how long-term contaminant exposure might impact the California condor recovery effort, and has important implications for other scavenging species exposed to lead and other environmental contaminants worldwide. Future study is needed to investigate whether the altered hormonal stress response is impairing the fitness, survival and reproduction of wild condors

Glucocorticoid measurement in plasma, urates, and feathers from California condors (Gymnogyps californianus) in response to a human-induced stressor.

Vertebrates respond to stressful stimuli with the secretion of glucocorticoid (GC) hormones, such as corticosterone (CORT), and measurements of these hormones in wild species can provide insight into physiological responses to environmental and human-induced stressors. California condors (Gymnogyps californianus) are a critically endangered and intensively managed avian species for which information on GC response to stress is lacking. Here we evaluated a commercially available I125 double antibody radioimmunoassay (RIA) and an enzyme-linked immunosorbent assay (ELISA) kit for measurement of CORT and GC metabolites (GCM) in California condor plasma, urate, and feather samples. The precision and accuracy of the RIA assay outperformed the ELISA for CORT and GCM measurements, and CORT and GCM values were not comparable between the two assays for any sample type. RIA measurements of total CORT in condor plasma collected from 41 condors within 15 minutes of a handling stressor were highly variable (median = 70 ng/mL, range = 1-189 ng/mL) and significantly different between wild and captive condors (p = 0.02, two-tailed t-test, n = 10 wild and 11 captive). Urate GCM levels (median = 620 ng/g dry wt., range = 0.74-7200 ng/g dry wt., n = 216) significantly increased within 2 hr of the acute handling stressor (p = 0.032, n = 11 condors, one-tailed paired t-test), while feather section CORT concentrations (median = 18 pg/mm, range = 6.3-68 ng/g, n = 37) also varied widely within and between feathers. Comparison of multiple regression linear models shows condor age as a significant predictors of plasma CORT levels, while age, sex, and plasma CORT levels predicted GCM levels in urates collected within 30 min of the start of handling. Our findings highlight the need for validation when selecting an immunoassay for use with a new species, and suggest that non-invasively collected urates and feathers hold promise for assessing condor responses to acute or chronic environmental and human-induced stressors

California condor poisoned by lead, not copper, when both are ingested: A case study

Abstract Lead poisoning from feeding on carcasses shot with lead‐based ammunition is a well‐known threat to wildlife. Thus, nonlead (e.g., copper‐based) ammunition is promoted as a safe alternative. We present a unique situation of a male California condor (Gymnogyps californianus) discovered with both a lead fragment and a copper bullet in his digestive tract simultaneously. We show that ingestion of a copper bullet did not result in elevated blood copper concentrations, while ingestion of a lead fragment contributed to lead toxicity. Our findings can inform nonlead ammunition outreach efforts by demonstrating that ingestion of a copper‐based bullet did not result in the poisoning of a California condor