By Sondra Murphy
In extreme rat infestations, even those disinclined to using poisons consider it. But care must be taken in order to avoid secondary poisoning of pets or accidental poisoning of pets and children. Private pest control companies are sensitive about using rat baits that will not contribute to unwanted poisonings.
“Inside a structure, we start with a trap,” said Robert Wolpe of Ojai Termite and Pest Control. “Many homes can be sealed up where the rats are getting into the home.” Monthly baiting services are also offered to keep the rodent population from spreading. For exterior rat abatement, Wolpe uses baits that attach to the ground and cannot be tampered with by children or pets.
“There’s fear about baiting because most people don’t know there are ways to do baiting in a safe manner,” Wolpe said. “Rats are just looking for a place to nest and also water and food.” Eliminating such temptations helps reduce rodent infestations from individual properties.
While humane societies do not advocate the use of poisons for rodent control, Jolene Hoffman, director of Ojai’s Humane Society of Ventura County, said that she understands the frustration of those dealing with this rat infestation. “With the numbers of animals they’re dealing with right now, I don’t see what other choice they have,” said Hoffman. “These are wild rats, so if they trap them, they’re only going to get one at a time.”
Most retail rodent poisons contain an anticoagulant called warfarin, which risks secondary poisoning. Mice or rats consume low dosages of the poison over several days, eventually dying from internal hemorrhaging. Anticoagulants are particularly effective because they are tasteless and odorless, so rodents do not become bait shy after initial consumption. In addition to its secondary poisoning risks, warfarin comes in the form of blue pellets that may look attractive to children or pets.
The risk of secondary poisoning depends on several factors. Poison manufacturers create low-dosage baits so if a larger animal later eats a poisoned rodent, it does not necessarily harm it. However, if there is enough undigested poison in the rat’s throat or stomach, secondary poisoning is possible, depending on the weight of the predator.
When rodents are very hungry, they may consume more poison than expected with usual foraging behavior and continue to eat more poison while initial pellets are being digested. If a predatory animal consumes several poisoned rodents, accumulative poisoning is also possible.
“Anything that carries anticoagulants can be detrimental to raptors,” Kim Stroud of the Ojai Raptor Center said last spring. Both domesticated and poisoned rats would have reduced natural defensive behaviors, such as coming out in the open during the day, said Stroud. The predator’s weight influences the chance for secondary poisoning, and whether it sustains internal injuries or dies.
Secondary poisoning most commonly causes liver hemorrhaging. Visual symptoms in pets include excessive salivation, agitated or hyperactive behavior, severe thirst, and loss of muscle control.
The Ojai Raptor Center has suggestions for safer rodent control by using poisons that do not contain anticoagulants. One is called Rampage. Another is Generation.
Ventura County rat abatement techniques may be found in English and Spanish at ventura.org/rma/envhealth. Once there, choose general information to find rat control. Ojai Termite and Pest Control may be reached at 646-6504. For more information about pet-safe pesticides, visit the Raptor Center’s web site at ojairaptorcenter.org. For more information about rat rescue efforts, visit weecompanions.com.