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PNAS:广泛存在于极度濒危的加利福尼亚秃鹰中的铅中毒

PNAS:广泛存在于极度濒危的加利福尼亚秃鹰中的铅中毒

一项研究表明加利福尼亚秃鹰中存在着广泛的铅中毒,并且提出这种极度濒危物种的种群在缺少了当前的密集管理举措的情况下可能再度衰退。铅中毒是1982年加利福尼亚秃鹰几乎灭绝的一个关键因素,当时全世界只有22只加利福尼亚秃鹰。Myra E. Finkelstein及其同事发现,加利福尼亚的秃鹰尽管有明显的复苏,但它们仍然长期暴露在有害水平的铅里。将近1/3的秃鹰血样表明导致显著的亚临床健康效应的铅暴露,而且大约20%的自由飞行的鸟的血铅水平需要临床干预从而防止发病率和死亡率。秃鹰是专性食腐动物,而且被认为从被铅弹药击中的动物尸体中摄入了铅。同位素分析证实了铅弹药是秃鹰铅中毒的主要来源,而且该研究还提示近来在秃鹰栖息地部分禁用这种弹药仍然无法减少这种鸟的铅暴露。种群统计分析表明这种秃鹰表面上的恢复仅仅是由于正在进行中的密集管理。这组作者说,铅暴露仍然是对加利福尼亚秃鹰的一个重大威胁,而且如果暴露不减少,目前的种群将继续需要永久性的密集管理干预。

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Lead poisoning and the deceptive recovery of the critically endangered California condor

10.1073/pnas.1203141109

Endangered species recovery programs seek to restore populations to self-sustaining levels. Nonetheless, many recovering species require continuing management to compensate for persistent threats in their environment. Judging true recovery in the face of this management is often difficult, impeding thorough analysis of the success of conservation programs. We illustrate these challenges with a multidisciplinary study of one of the world’s rarest birds—the California condor (Gymnogyps californianus). California condors were brought to the brink of extinction, in part, because of lead poisoning, and lead poisoning remains a significant threat today. We evaluated individual lead-related health effects, the efficacy of current efforts to prevent lead-caused deaths, and the consequences of any reduction in currently intensive management actions. Our results show that condors in California remain chronically exposed to harmful levels of lead; 30% of the annual blood samples collected from condors indicate lead exposure (blood lead ≥ 200 ng/mL) that causes significant subclinical health effects, measured as >60% inhibition of the heme biosynthetic enzyme δ-aminolevulinic acid dehydratase. Furthermore, each year, ∼20% of free-flying birds have blood lead levels (≥450 ng/mL) that indicate the need for clinical intervention to avert morbidity and mortality. Lead isotopic analysis shows that lead-based ammunition is the principle source of lead poisoning in condors. Finally, population models based on condor demographic data show that the condor’s apparent recovery is solely because of intensive ongoing management, with the only hope of achieving true recovery dependent on the elimination or substantial reduction of lead poisoning rates.

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