Chlorophacinone and diphacinone are anti-coagulants. Both cause death by bleeding and/or dehydration by thinning the blood, preventing it from clotting. Both pose a slightly greater risk to non-target species than carbon monoxide, aluminum phosphide, or zinc phosphide; however, there is an antidote to anti-coagulant exposure.
Anti-coagulant baits do pose a risk of secondary toxicity. Birds or animals that feed upon the carcass of a poisoned prairie dog may be exposed to enough poison to be dangerous. Grain eating animals are also at risk of poisoning by the bait itself, as are fish, if the bait is applied to surface water. As such, no livestock should be on the site for a month or more after application. Absolutely no broadcasting of either bait is allowed for prairie dogs.
The effectiveness of both zinc phosphide and both anti-coagulant baits can vary greatly depending on the condition of the available vegetation and the health of the prairie dog colony. Zinc phosphide can be used from July through January; Rozol® and Kaput-D® baits can be used from October 1st though March 15th. All three seem most effective later in the season, when all of the available vegetation is dormant and conditions very dry. Late December through early March is optimum.
Both anti-coagulant baits are limited to rangeland and adjacent non-crop areas, which makes them unavailable for most urban and suburban settings as well as farmland and orchards.
The EPA currently has three baits registered for prairie dog removal: Zinc phosphide, Rozol® and Kaput-D®.
Application consists of one or two pre-baiting trips where plain grain is applied to entice and train the prairie dogs to eat the bait. The bait is applied after the prairie dogs show that they have accepted the pre-bait. The bait is to be applied at the rate of 1 teaspoon per active mound and it is placed on or near the mound. Zinc phosphide application can take place from July through January.
Zinc phosphide poses a very slight risk of secondary poisoning, although the carcass of a prairie dog is not generally toxic enough to cause any harm to a larger animal that may feed upon it. It does, however, pose a threat to non-target species that have access to the bait itself. All livestock and pets should be kept from the area for at least a couple of weeks and great care should be taken to avoid any location where waterfowl may access the bait. Frost, dew, rain, and sunlight will eventually degrade any unconsumed bait.
Zinc phosphide bait, like its fumigant cousin, kills prairie dogs with the use of phosphine. Once the zinc phosphide bait is consumed, it reacts with moisture in the gastric juices to liberate phosphine gas. The prairie dog inhales the gas (and dies by suffocation
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Rozol ®(chlorophacinone) and Kaput-D® (diphacinone) are anti-coagulant baits for prairie dog removal. Each dose of bait must be placed 6” down inside each active burrow. The prairie dogs begin to die off 4 to 5 days after consuming a lethal dose of the bait. According to the label, the site must be visited by the applicator starting four days after application is made and then every two days for 14 to 21 days to dispose of any carcasses and clean up any bait that may be out onto the surface.
Rocky Mountain Wildlife Services, Inc. © 2016
Battling Prairie Dogs in Colorado, Southern Wyoming and Western Nebraska for over 30 years.