Birth control could replace bullets in race to reduce growing threat
To many farmers, the only good coyote is a dead coyote. Thousands of the dog-like animals are shot and killed each year to prevent attacks on livestock, wildlife and people. Now, as the coyote population expands to include urban areas, a humane alternative may be on the horizon.
Based on observations that coyotes without puppies are less likely to attack livestock, scientists with the U.S. Department of Agriculture (USDA) are working to produce new fragrances to bait and trick the elusive animals into consuming birth control drugs. Fewer pups means fewer attacks, which should result in fewer coyote shootings, the scientists say. The findings are reported in the May issue of the Journal of Agricultural and Food Chemistry, a peer-reviewed publication of the American Chemical Society, the world's largest scientific society.
At present, there is no reliable coyote contraceptive. However, USDA researchers are testing potential candidate drugs.
Fragrances, or chemical attractants, are nothing new to coyote management. They have been used for years to lure coyotes into traps to reduce attacks on livestock. To take advantage of the coyote's keen sense of smell, these fragrances have often been creative mixtures of blood, urine and other fluids from a variety of animal sources. Because of this variability, the effectiveness of these fragrances has been unpredictable, researchers say.
"Coyote management requires specialized attractants for the targeted delivery of drugs and vaccines and for the effective operation of traps," says Bruce A. Kimball, Ph.D., principal investigator of the study and a chemist with the USDA's National Wildlife Research Center in Fort Collins, Colo. "Attractants must provoke behavior that will make them respond appropriately."
In an effort to develop simpler and more reliable fragrances to optimize effectiveness, Kimball selected 33 complex coyote attractants for chemical analysis. Based on this analysis, seven promising but less complex synthetic fragrances were produced, he says. Each of the new fragrances was tested among 28 coyotes -- half male, half female -- whose behaviors were monitored and recorded.
Among the animals studied, female coyotes were the first to respond to the chemicals, the researchers say. This suggests a possible target for delivering birth control drugs to female coyotes to prevent births, says study co-author J. Russell Mason, Ph.D., a researcher with the USDA's National Wildlife Research Center in Logan, Utah.
The purpose of reducing births is not to decrease the coyote population, but to change the animal's feeding and predatory behavior, Mason says. The feeding habits of coyotes are based largely on whether they have offspring, he explains. Coyotes with puppies have a constant need for food in order to provide energy for their pups. As a result, they seek out larger prey, especially lamb and sheep. Coyotes without puppies have a smaller need for food and tend to choose smaller prey, like rodents and rabbits.
One of the new fragrances tested elicited strong chewing behavior, a response that would be useful for getting the coyotes to absorb vaccines, says Mason. Vaccines must be delivered to the lining of the mouth to be effective, while a vaccine that is gulped would bypass the mouth and not work properly, he explains. Researchers hope that this method can be used to deliver rabies vaccines to coyotes, which are a primary carrier of the disease. They can transmit it to dogs, which can pass it to humans.
Although the new coyote management approach using the new fragrances may take several years to develop and apply, researchers believe that it will ultimately cut down on lethal methods currently in use, such as shooting.
Farmers are particularly concerned about coyote attacks because the sheep population in this country has declined more than 25 percent within the past decade, with coyote attacks cited as a major cause of this decline, according to one USDA study. The agency estimates that coyote attacks on livestock have cost farmers millions of dollars in lost earnings.
While no one knows the exact size of the coyote population in this country, their range is expanding. They are more numerous in Western states, but their range now includes nearly every state and is rapidly extending eastward to include many urban areas. In addition to posing a threat to livestock, coyotes are also a danger to deer, antelope and some endangered species. Coyotes rarely attack humans, although the number of reported incidents has increased, the researchers say.
The online version of the research paper cited above was initially published April 21 on the journal's Web site.
A nonprofit organization with a membership of 161,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio. http://www.acs.org.
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