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The C.A.S.H. Courier

ARTICLE from the Winter 2009 Issue

The Ineffectiveness of Coyote Hunting

 Dr. Robert Crabtree, President and Founder of YELLOWSTONE ECOSYSTEM STUDIES

Biology Department, Montana State University, answers the question “What effect does reduction of coyotes (older than 6 months) have on the remaining population?” He had heard claims that reduction of adult coyotes would lessen predation on domestic sheep or game animals such as mule deer or antelope. He refutes those claims with the following points:

Most reduction programs are indiscriminate in nature, meaning the individuals removed (killed) are probably not the offending individuals. Even if some offending individuals are removed, there is great likelihood that the responses described below will take place anyway. Although removal of offending individuals can temporarily alleviate predation rates, the alleviation is usually short-term and likely has long-term side-effects that make control activities ineffective. It can not be over-emphasized how powerfully coyote populations compensate for population reductions. Both evolutionary biology and the results of my research the last three years indicate that the basis of this resiliency is embedded in the evolutionary past of the coyote.

(1) Actual reduction in the density and number of coyotes does occur but is compensated by immediate immigration into the reduction area by lone animals or shifts in surrounding social groups.

(2) Reduction results in a smaller social group size which increases the food per coyote ratio. This food surplus is biologically transformed into higher litter sizes and higher litter survival rates. The increase in food availability improves the nutritional condition of breeding females which translates in higher pup birth weights and higher pup survival.

(3) Reduction causing higher pup survival is fundamentally a function of the general mammalian reproductive strategy that delays the majority of reproductive energetic investment beyond the gestation period, e.g., young pups. Thus, the normal litter of six pups has a good chance of (a.) surviving the typically high summer mortality period and, (b.) being recruited into the pack the following winter as adults.

(4) Reductions of adult-sized coyotes 6 months or older results in smaller pack size, which leaves fewer adults to feed pups. This may further add incentive for the remaining adults to kill larger prey as well as putting pressure on the adults to select for the most vulnerable prey close to areas of human activity. Because predators like coyotes also learn what is appropriate food when they are pups, and are reluctant to try ‘new’ food sources unless under great stress (such as having to feed a large litter of pups) reduction programs, in effect, may be seen as forcing coyotes to try new behaviors (eating domestic livestock) which they would otherwise avoid.

(5) Reductions cause an increase in the percentage of females breeding.

(6) Reduction causes the coyote population structure to be maintained in a colonizing state. For example, the average age of a breeding adult in an unexploited population is 4 years old. By age 6 reproduction declines, whereby older, alpha pairs maintain territories but fail to reproduce. This may eliminate the need to kill sheep or fawns in the early summer in order to feed pups. Exploiting or consistently reducing coyote populations keeps the age structure skewed to the young and in a state of constant social and spatial flux. Therefore, the natural limitations seen in older populations are absent and the territorial, younger populations are much more productive.

(7) Reductions cause young adults (otherwise prone to dispersing) to stay and secure breeding positions in the exploited area. This phenomenon is well-documented. There are other demographic responses that negate the effectiveness of control practices but the aforementioned covers the most important.

Alternate prey The preferred, natural prey of coyotes is rodents, such as voles and jackrabbits, animals that require ample cover and supplies of forage. Because domestic livestock grazing has been increased on many western range lands, grasses and protective cover have been greatly reduced, leaving coyotes with fewer preferred prey. Coyotes only switch to alternative prey such as livestock when a preferred prey item is absent or in low numbers. Current grazing practices may therefore be seen as a cause of predation on other species like domestic sheep

We do not yet know how coyote populations will respond once predator reduction programs are terminated. We should ask, “Are there other non-lethal management alternatives that may be effective in reducing predation on domestic livestock?” In conclusion, the common practice of reducing adult coyote populations on western rangelands is most likely ineffective and may even increase the number of lambs, fawns, and calves killed by coyotes.

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