Rodent bait a danger to wildlife

March 5, 2012

Got rats? As appealing as it may seem to have your rodent intruders done away with the drop of a few blue pellets, the city of San Francisco is telling its citizens: “Don’t take the Bait.”

The campaign seeks to turn public opinion away from best-selling rat and mouse poisons for the sake of wildlife and the environment.  The poisons, which sell under the label d-CON as well as others, kill with one serving of pellets. Quick and clean, or so it would seem.  

The trouble is that the poison-infused rodents eventually become toxic prey to any creature higher up on the food chain. There are numerous alternatives to manage a pest problem, but sometimes the classic, most basic methods can be most effective, said Chris Geiger, San Francisco’s municipal toxics coordinator.

“The number one thing to do is to exclude the pest, and take away their food source,” Geiger said. Failing that, he said to stick to snap traps, which are “extremely effective,” albeit messy. 

San Francisco’s request of its environmentally conscious citizens is entirely voluntary. Though the U.S. Environmental Protection Agency determined in 2008 that single-feed (as opposed to multiple feed rodenticides that kill on multiple feedings) are an “unreasonable risk” to wildlife and the environment, the agency’s efforts to ban the products altogether have been stymied by legal action by pesticide manufacturers.

San Francisco officials hope that by asking consumers and retailers to take the lead in finding other pest management options they can mitigate environmental damage, since it could be a long time, if ever, before a regulation gets passed. 

“Manufacturers are counting on the fact that the regulations [are] so wonky and complicated that most people won’t try to understand what’s going on. These are dangerous products, but they’re on the shelf and being sold anyway,” Geiger said.

The poisons work in several ways. Some inhibit an animal’s ability to produce vitamin K, which is necessary in the reproduction of red blood cells and the formation of blood clots. The animal dies from internal bleeding. Others, primarily aimed at larger pests such as a gopher, attack the nervous system (imagine a terrible charlie horse, only in the brain). The d-CON product website trumpets such methods as a “simple, mess-free solution to rodent problems.”

Still, because the single-feed poisons are so quick and clean, the city of San Francisco plans to keep using them in limited and controlled ways. For example, the city sends out trained workers to deploy pellets into the sewer system, where rodents are many and predators few.  The poison pellets are encased in wax to prevent the spread to waterways and then, rather than being scattered randomly, the pellets get hung from a wire in an area that can be easily monitored.

About the Author

Chris Torres is a Bay Nature editorial volunteer.

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