In 2020, Tufts Wildlife Clinic Director Maureen Murray, V03, published a study that showed 100% of red-tailed hawks tested at the clinic were positive for exposure to anticoagulant rodenticides (ARs). Such exposure occurs when these chemicals are used to kill mice or rats, which eat the poison, and the birds eat the poisoned prey. Now, Murray is expanding that research with a new study published recently in the journal Environmental Pollution, which found that another type of rodenticide—a neurotoxicant called bromethalin—also can bioaccumulate in birds of prey.
“We understand very well that ARs can remain active once they’ve been ingested by the prey, and when a bird of prey or other species ingests that animal, the predator will be poisoned by the residues. But with bromethalin, adequate studies to prove or disprove whether that type of secondary poisoning can happen don’t exist yet,” said Murray, who is also associate clinical professor at Cummings School of Veterinary Medicine. “The point of our new study is to answer a simple question: would we be able to find evidence of bromethalin exposure in birds of prey coming into the clinic? And the answer is yes, we found it.”
Murray and co-author Elena Cox, the Shalin Liu Fellow in Wildlife Medicine and Education, sampled the birds in the same way as the birds in the 2020 AR study. The birds of prey were from the same geographic population of birds in which Murray has found high exposure to ARs over time and were from the same four species of hawks and owls that were included in her previous studies. They found evidence of bromethalin exposure in about 30% of the birds of prey that were sampled.
Read more at: Tufts University
The findings show the ongoing, widespread exposure of birds of prey (such as red-tailed hawks, pictured) in the northeastern United States to anticoagulant rodenticides, underscoring the need for reevaluation of mitigation measures intended to decrease this risk. (Photo Credit: Anna Miller / Tufts University)