Sealing gaps and securing food can fight rodent infestations while protecting predators

Sealing gaps and securing food can fight rodent infestations while protecting predators Sadie Harley Scientific Editor Andrew Zinin Chief Editor Mice and rats can spread dangerous viruses and bacteria, trigger asthma attacks and damage property with their constant gnawing. So when rodents get indoors, most people take action to help keep their home safe. The problem? Some rodent poisons can have unintended effects on wildlife. Anticoagulant rodenticides—which prevent blood from clotting and cause rodents to die from internal bleeding—are a commonly used type of rodent poison. Unfortunately, anticoagulant rodenticides can be transferred to predators such as hawks and owls when these birds consume poisoned prey animals. This exposure through their prey can result in the death of the predators. "No one wants rats or mice in their home," said Maureen Murray, V03, the Shalin Liu Professor of Wildlife Medicine at Cummings School of Veterinary Medicine at Tufts University. "While I am often asked if some poisons are safer for wildlife, the words 'safe' and 'poison' inherently do not go together." Murray, a wildlife veterinarian and director of Tufts Wildlife Clinic, has spent two decades studying the effects of rodenticides on wildlife. In a 2020 publication, she found that 100% of red-tailed hawks included in the study were positive for exposure to anticoagulant rodenticides. The study, published in Environmental Toxicology and Chemistry, also found that 91% of the birds tested positive for two or more different anticoagulant rodenticides. In a 2023 study that analyzed four species of birds of prey for rodenticides, she found that 96% of the tested birds were positive for anticoagulant rodenticides. Published in Environmental Pollution, the study also found that 81% of the birds overall were exposed to two to four different anticoagulant rodenticides. The danger comes from how these poisons work. Rodents often survive for several days after eating bait—and may continue feeding during that time. As a result, their bodies can contain enough poison to kill the hawks, owls, foxes, coyotes and other predators that eat them. Because these chemicals accumulate in the liver, predators that repeatedly consume poisoned prey can build up lethal amounts over time, even if each individual meal contains only a small dose. The 2023 study was also the first to document evidence of exposure to a different type of rodent poison in birds of prey: bromethalin, a neurotoxic rodenticide that has been used more frequently in recent years as an alternative to anticoagulant rodenticides. Murray and co-author Elena Cox, former Shalin Liu Fellow in Wildlife Medicine and Education, found that 30% of birds tested for the study were positive for residues of the toxic metabolite of bromethalin. "There is little study on the potential for bromethalin to cause poisoning in predatory wildlife. Additionally, bromethalin poisoning is hard to diagnose as the signs it causes are nonspecific and resemble other causes of neurologic abnormalities," said Murray. "There is currently not enough data to know if bromethalin poses a lower risk to wildlife than anticoagulant rodenticides." However, there are nonchemical ways to manage rodent problems while reducing risks to wildlife and other animals. Murray shared the following tips. - Rodent-proof your home. The most effective rodent control starts with prevention, both indoors and outside. Store garbage, compost, grass seed and pet food in tightly sealed containers. Remove bird feeders if rodents are visiting them. Clean up pet waste. And seal openings where rodents can enter your home, particularly around sink pipes, kitchen appliances and cracks in the foundation. - Choose faster, more humane traps. "People often believe poisons are more humane than traps, but poisons do not necessarily result in a quick death," Murray says. Snap traps kill rodents much more quickly than poisons. She advises people to avoid glue traps, which can leave rodents suffering for hours or days and frequently injure birds, reptiles and other animals that become stuck accidentally. - Ask your pest control company about integrated pest management, which emphasizes prevention, home repairs and sanitation, alongside other control methods as needed. Eliminating food sources and thoroughly blocking entry points can solve rodent problems without chemical pesticides. - Ask what products your pest control company uses and how they reduce risk to wildlife. If a rodent infestation necessitates the use of chemical rodenticides, you can ask your pest control professional which products are being used and what steps they take to minimize potential exposure to wildlife. Initiating such a conversation ensures that your pest control professional can best partner with you to solve the problem without impacting wildlife. For Murray, protecting wildlife and protecting homes are not competing goals. "If you make your property less attractive to rodents in the first place, you'll protect your family, your pets and the wildlife that naturally helps keep rodent populations under control," she said. Journal information: Environmental Toxicology and Chemistry , Environmental Pollution Provided by Tufts University