Secondary poisoning

Secondary poisoning occurs when an animal containing traces of poison is consumed by another animal or human. Using rat poison (rodenticides) often kills more than just rats and mice. The primary poisoned animal transfers the poison to the consuming animal  — most commonly through the liver.

Using rodenticides can have negative effect on the ecosystems. Threat to your cat or dog is obvious, but also an increase in deaths of wild animals over recent years has been observed.

Common rodenticides with the highest risk for mammals include:

• ACR (Anticoagulant Rodenticides)
• Bromethalin
• Cholecalciferol (Vitamin D3)
• Phosphides

Studies documenting loss of wildlife

Mammals susceptible to secondary poisoning include humans, with infants and small children being the most susceptible. Pets such as cats and dogs, as well as wild birds, also face significant risk.

Birds of prey such as owls, hawks, eagles and other raptors are often carriers of rodenticides. A study in 2018 looked at two owl species in California. It showed 70% of northern spotted owls and 40% of barred owls were exposed to rodenticides.  

Larger animals like mountain lions, bears, bobcats, raccoons, coyotes and foxes have even higher exposure.  Testing from 2015-2016 shows rodenticide exposure in these animals is as high as 86%. Snakes and other reptiles can also be affected when feeding on rodents.  

Read the intimidating article about the use of rodenticides and how it affects wildlife.