Over the past few decades there has been a dramatic increase in the abundance of coyotes (Canis latrans) throughout the Midwest. As recently as the 1950s, coyotes were considered uncommon in Illinois; now there are probably over 30,000 living in the state. The reasons for the increase in abundance and expansion of the coyote's range over eastern North America are uncertain, but probably include the extirpation of competitors, such as gray and red wolves, from these areas.
Most people picture coyotes howling with the moonrise on some western desert landscape, not skulking around cornfields in central Illinois. In fact, coyotes flourish in a wide variety of habitats, but seem to prefer open environments. According to Don Hoffmeister in Mammals of Illinois, the early settlers called coyotes "prairie wolves" to distinguish them from the timber wolf, which occupied more densely wooded habitats. Only recently have coyotes become denizens of areas dominated by row-crop agriculture.
Coyote (Canis latrans) alive and well in Illinois. (photo courtesy U.S. Fish and Wildlife Service.)
How has the coyote adapted to this new habitat? What characteristics have allowed it to become so successful in spite of intense hunting and trapping pressure? Although coyotes have been extensively studied elsewhere, surprisingly little research has been conducted on coyotes inhabiting agricultural landscapes. Does the behavior of coyotes living in these areas differ from that of coyotes in more "natural" habitats?
A pilot study is attempting to answer some of these questions by investigating home range size and habitat use of coyotes in central Illinois. Coyotes are captured using padded leg-hold traps, then fitted with collars and radio transmitters, and released. Their movements are then followed by telemetry.
Tracking radiocollared coyotes is not easy! Two researchers monitor the movements of individual coyotes from trucks outfitted with special antennae and receivers. The researchers communicate by CB radio and record simultaneous "fixes" (directional bearings of the strongest radio signal) to locate the coyote at frequent intervals throughout the night. Coyotes are very wary, so trackers must be stealthy as well in order not to spook their subject with bright headlights, loud noises, or truck engine ignition when changing tracking locations. Each animal is followed all night for at least six nights. Mostly, successful radiotracking requires luck, patience, and lots of coffee.
Only two coyotes were radiotracked in the late summer of 1994. One of these was an adult male and the other was a subadult male, a coyote "teenager." The adult male had a home range covering about 13 square miles, and the subadult ranged over 39 square miles during July and August. These home ranges are very large compared to similar measurements reported from other habitats. For example, home ranges of coyotes in the western U.S. average about 6 square miles. Six more coyotes were radiocollared in March and April 1995 and are currently being radiotracked.
Illinois' largest predator hot on the trail of a potential meal. (photo by R.H. Barrett, American Society of Mammalogists.)
In addition to measures of home range size, habitat use will be determined by plotting locations of animals made at hourly intervals onto aerial photos of their home ranges. Understanding how coyotes use the landscape while hunting or traveling can provide insights into how they interact with other carnivores and prey species that might be concentrated in habitat features, such as hedgerows, fence lines, grassy strips, or small woodlots. If prey species become concentrated in areas that are used heavily by coyotes, these areas may act as "ecological traps." Prey species might be attracted to such areas because of apparently suitable cover or food resources but be exposed to greater risk of predation than if they spread out into other habitats.
The results of this study will help us design future, more detailed studies of the ecology of coyotes in agricultural landscapes. With luck, patience, and a contiunous supply of coffee, we'll learn more about the secretive habits of Illinois' largest extant predator.
Ed Heske, Center for Wildlife Ecology and Marty Miller, Department of Forestry, University of Illinois
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