Dr. Deer’s Prescription

Coyotes Have To Be Managed Too

By Dr. James C. Kroll

In 1972, I was finishing my doctoral dissertation in wildlife management at Texas A&M University. As a scientist in training at that time, being aware of the scientific literature was imperative. Keeping up on historical studies and the latest findings were considerably more difficult than in this age of Google searches.

My supervising committee expected to me to arrive at my dissertation defense, ready and able to discuss every known aspect of the topics presented in my paper. To do so meant hours of poring through hard copies of the various journals, as well as reading theses and dissertations produced by other graduate students from around the globe. My research was about as far away from coyotes as you could imagine, but while digging through a copy of an old bound thesis, I ran across one completed in the 1930s on sheep and goat ranching in the Texas Hill Country.

In those days, a thesis was not the polished, printed document it is today. Photographs had been carefully pasted in

In the last two decades, southeastern deer biologists have literally come to “call for the heads” of coyotes. Several studies have shown coyotes do negatively impact deer herds.

The idea that the entire predator-deer ecosystem has to be managed is alien to professionals and the public alike. Predators often are considered as “charismatic megafauna,” not unlike public perception of invasive wild horse populations. The idea of killing them is repugnant.

place using rubber cement, and some fell out when I opened the copy. I was much more “sophisticated” in producing my dissertation, by using offset printing.

The author made an interesting recommendation in his conclusions. He urged that sheep and goat ranching be discouraged because it would allow the coyote to bridge the Edwards Plateau into the southern United States. Some 70 years later, the coyote was well-entrenched all the way to New England and had spread northeastward through the Great Lakes states. Coyotes became totally ubiquitous to North America by following a two-front invasion. Small livestock ranching may have given coyotes a boost across the Edwards Plateau.

As a young deer biologist in the 1970s, I became a member of the Southeast Deer Study Group, made up of government and university biologists across the Southeast. Each year we gathered at a different state to present preliminary findings on a host of exciting studies on whitetails. Those were “heady” times, since much of what folks now take for granted as “established facts,” were discovered by that group of scientists.

One of my favorite aspects of the annual meeting was the opportunity for passionate young biologists to argue biological concepts. One of these was the impact of predation on deer, in most cases by the coyote. In the early days, only the Texas biologists considered coyotes as a significant threat to whitetails. After all, they had not yet spread across the South and up the Atlantic Coast.

The prediction made by that Texas A&M graduate student that coyotes would spread southeastward in response to sheep and goat ranching was just beginning to materialize. Yet, once coyotes crossed the Texas Hill Country, I became convinced about a direct correlation between rapidly growing deer populations and coyote range expansion. Yes, many potential prey species for coyotes exist, including rabbits, rats, mice and birds. However, there’s a rule in predator-prey theory that states predators will focus their efforts on the prey that provide the most amount of food per unit pursuit effort. Whitetails and coyotes became members of the same ecosystem.

In the last two decades, the southeastern deer biologists, who once argued coyote predation is negligible, have literally come to “call for the heads” of coyotes. Several studies have shown coyotes can and do indeed negatively impact deer herds. Research studies on predation generally focus on a single predator species’ impact. As the original suite of predators returned—coyotes, bobcats, bears, etc.—scientists discovered the concept of additive impacts, that is, considering the sum of contributions by all predators. You also have to factor in nonpredator mortality agents such as disease, automobile accidents and habitat deterioration.

The result is a new way of looking at deer management that I refer to as Ecosystem Deer Management. As I learned quite clearly during my stint as Wisconsin’s Deer Trustee, the idea that the entire predator-deer ecosystem has to be managed is alien to professionals and the public alike. Predators often are considered as “charismatic megafauna,” not unlike public perception of invasive wild horse populations. The idea of killing them is repugnant.

We really ran into a “firestorm” in Wisconsin. We supported setting population goals for wolves, a super-charismatic megafauna, in spite of the fact populations are growing alarmingly throughout the Great Lakes states. Yet to date, I don’t know of a single state that has produced a deer ecosystem management plan, that simultaneously considers impacts of habitat on deer herds, impacts of deer herds on predators and vice-versa.

Focusing just on the coyote for now, I assert we are dealing

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with two distinctly different situations regarding deer ecosystem management: mesic (wet) and xeric (dry) climates. Note that coyotes once occurred primarily in dry climates, where extremes create highly dynamic prey population fluctuations. For some time, we have been conducting a deer ecosystem management/research program on a very large ranch near Piedras Negras. This work includes intensively monitoring recruitment rates of whitetails, which as with South Texas, often fluctuate significantly.

We have learned water availability and distribution is the greatest recruitment driver. That should come as no surprise to you. In addition, we are doing all the standard practices such as supplemental feeding and brush management. We have generally considered coyote predation as acceptable in most cases. However, we have come to the position, careful monitoring of coyote numbers and making selective reductions in numbers is the best approach.

It’s an entirely different story within the new range of coyotes. Remember, they only arrived in the eastern U.S. during the last 50 years or so (see map), and although the climate may be more stable, the deer ecosystems are not. Recent studies have shown coyote predation has a much larger impact on recruitment than ever imagined. A study in South Carolina by the U.S. Forest Service concluded in southeastern deer management, you have to consider the impact of coyotes on recruitment and the hunter harvest. It’s possible to collapse herds if you do not. In my early days, when a landowner asked how many does he should kill, the flippant answer often was, “Can you get .30-06 shells in barrels?” That attitude came back to bite us when coyotes joined the ecosystem. Modern deer biologists are changing their attitudes about coyote predation, but they still fall into the same old trap. The concept of setting predator management goals, along with strategies to accomplish them, remains ignored. Some biologists try to use habitat management to increase fawning cover. Yet, although it helps, studies also show not by much. Again, it takes an integrated and targeted approach. Predator management in many states is extremely difficult, due to regulations aimed at protecting rather than managing predators. At Turtle Lake and Grand Rack Hunting Clubs in Michigan, we have developed a monitoring system to determine the extent of predator management needed. We use small mammals, particularly rabbits, as our “canaries in a coal mine!” We do the same thing here at our research center in East Texas. When rabbit counts decline, we step up coyote removals until rabbits return. This does not require eradication of coyotes, only numbers management. But it takes more than casual opportunity shooting. At Grand Rack Club, biologist Adam Osmun has become particularly skilled at coyote management, using monitoring, legal trapping and shooting stations. Prior to initiating the program, true recruitment rate for the deer herd was below 30%. In 2022, recruitment rate was an unheard of 94%—not fawn crop, but true recruitment. Of course, we use sound habitat and deer herd management strategies, but it’s clear coyote management works when it’s part of an ecosystem plan.

Deer management is far more complicated than when I began my career some 50 years ago. It was easy to manage deer then, with growing herds, few predators and other mortality agents. Today, we have to learn to develop management strategies aimed at the deer ecosystem and each of its component parts.