Behavioral shifts mask the success of legislation and outreach for endangered species recovery

TL;DR

Legislation and outreach efforts have successfully reduced lead exposure in California condors, but changing behaviors in both condors and humans initially masked these benefits.

Contribution

The study reveals how behavioral shifts can obscure the effectiveness of conservation actions, emphasizing the need for comprehensive evaluations.

Findings

Lead ammunition bans and outreach efforts significantly reduced condor blood lead levels.

Increased condor foraging and human hunting of wild pigs explain the initial rise in lead exposure.

Changing ecological conditions can mask the true impact of conservation interventions.

Abstract

A fundamental challenge in conservation is assessing the efficacy of recovery actions to optimize endangered species management. Considerable recent attention has focused on effective measures to counter the endangerment of avian scavengers, which have declined worldwide, primarily due to poisoning. One iconic example is efforts to recover the critically endangered California condor (Gymnogyps californianus), whose leading cause of death is poisoning from ingesting lead-based ammunition in carcasses. Despite enormous resources expended in California, USA, including implementation of public outreach campaigns and two legislative bans on lead ammunition, lead-related mortality of condors has increased. Here we show that two types of behavioral shifts explain the observed increases in condor lead exposure: wilder foraging and ranging by condors and increased shooting of wild pigs (Sus scrofa) by humans. After accounting for these trends, we show that both lead ammunition bans and public outreach efforts have significantly reduced condor blood lead levels in California, lowering mortality. Our analyses uncover a dynamic in which changing ecological conditions mask the true efficacy of legislation and outreach. Given rapid global change, such dynamics are likely operating in many settings, underscoring the importance of comprehensive evaluations of recovery actions, which can be obscured by shifting behaviors and threats.

Despite enormous resources expended, lead exposure in endangered California condors has risen. The authors show lead ammunition bans and outreach are effective, with changing hunting patterns and wilder condor behavior explaining exposure increases.

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