Natural Rodent Control

Last year a mountain lion was found dead in the mountains north of Los Angeles. While the reasons for the death are uncertain, signs point to the six compounds of a rodenticide discovered in his system. Despite its danger to wildlife, rat poisons and other rodenticides continue to be used to maintain rodent and pest populations. A recent study, however, could change public use of rat poisons as they demonstrated that birds of prey were not only more effective in lowering rodent populations, but more economical.

Barn owls, bobcats, and other predator species often eat prey that have ingested these poisons. Poisons and other contaminants are known to move up the food chain from prey to predator species. Anticoagulant rodenticides interrrupt blood-clotting in animals and can cause uncontrolled bleeding and lowered immune systems, which often leads to mange; a microscopic mite that causes skin lesions.

Researchers from The Ventura County Watershed Protection District completed a raptor study that would compare methods of controlling ground squirrel populations along levees and dams. One method observed was the continuation of their use of rodenticides at bait stations while the other would be to attract birds of prey. Raptor perches were installed all along the levees and were able to attract red-tailed hawks, great horned owls, and barn owls. Bones from rodents were found in 107 raptor pellets being collected in the study area demonstrating their effectiveness. When examining the sites, researchers found a 47% reduction in rodent burrows in the areas where perches were installed!

The study estimated an annual saving of $7,500 per levee from the current rodenticide program to a raptor program. Not only is this great for the county, but this could inspire more agencies to adopt the Raptor Program which could reduce the amount of wildlife being affected by rodenticides.

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