Quantifying the impact of chronic lead toxicity on the American Bald Eagle (Haliaeetus leucocephalus) population in the Great Lakes Region
An American Icon, the bald eagle, was placed on the endangered species list in 1967 after its population hit critically low levels due to the adverse reproductive effects of DDT. After DDT was banned in 1972, another environmental contaminant continued to affect their recovery—lead. Ingestion of lead-based ammunition was shown to be the eagles’ top cause of death, resulting in a 1991 ban of its use for waterfowl hunting. Nearly thirty years later, cases of lead-toxicity in the bald eagle population continue into the present. Noting that the 1991 ban excluded other hunting game, the main source of lead is now linked to the fall and winter big game hunting seasons. This coincides with the eagles’ scavenging season, resulting in an annual addition of lead to the eagles’ diet. Due to their acidic stomach environment, the eagle is especially lead-free to lead-toxicity. Lead-toxicity may cause severe clinical symptoms (including death), but also more subtle, chronic symptoms. A bald eagle may suffer from chronic toxicity for many years of its life, resulting in continual physiological damage and affected biological mechanisms, including reduced fertility and voracity. Its ecological role as both a scavenger and apex predator make the eagle a valuable resource in the assessment of the Great Lakes ecosystem’s health. In order to quantify the impact of lead-contaminated food sources on the bald eagle’s population of the Great Lakes, we formulated a system of ordinary differential equations to show the progression through the stages of lead-toxicity and its role in the eagle’s population dynamics. We compared the impact of the source of contamination verses treatment of lead-toxicity. We found the bald eagle population is sensitive to its source of lead-contamination.
Christine Brasic - University of Wisconsin-Whitewater
Latimer Harris-Ward - University of the Pacific
Gregoire Moreau - Medgar Evers College
Carlos Bustamante-Orellana - Arizona State University
Jordy Cevallos-Chavez - Arizona State University