PM11 Wildlife Ecotoxicology
Exhibit Hall
8:00 AM - Monday
(PM179) Secondary poisoning of captive raptors by brodifacoum at the Amicalola Falls State Park.
Mastrota, F.1, Erickson, W.1, 1 US Environmental Protection Agency, Washington, DC, USA
ABSTRACT- Several raptors were housed in mews at the Amicalola Falls State Park. In November of 2003, a red-tailed hawk (Buteo jamaicensis) and a barn owl (Tyto alba) began showing abnormal physical and behavioral symptoms. The hawk produced an odd-looking pellet that indicated it had eaten something other than its normal diet of white rat pups. Both birds died within a few days. Two great horned owls later showed similar symptoms and were treated with vitamin K. A dead rat was also discovered in a hole in the back of one of the raptor cages. Second-generation anticoagulant rodenticides were in used at the park at the time of the incident to control rats around a lodge and intern housing. Necropsy of the bird carcasses by the Southeastern Cooperative Wildlife Disease Study found moderate to severe clavarial hemorrhage in both birds and moderate focal myocardial hemorrhage in the barn owl. Microscopic examination also showed moderate to severe multifocal hemorrhage in the owl. Microbiological tests were negative. A fresh liver and kidney samples from each bird were screened for heavy metals and organic chemicals, including anticoagulant rodenticides. The only chemical detected in either bird was the rodenticide brodifacoum, with concentrations measured in the at 77 ppb in the hawk and 7 ppb in the owl. Despite the very low levels detected, the evidence of this case strongly indicates that the birds die from secondary poisoning by feeding on rats that were exposed to brodifacoum. Brodifacoum is highly persistent and extremely toxic to birds, with LD50's ranging from 0.26 to 10 mg ai/kg bw. This and other cases show that second-generation rodenticides can cause lethal hemorrhaging in raptors even when liver levels are less than 1 ppm.
Key words: brodifacoum, anticoagulant rodenticides, raptors