What are the effects of coyotes on deer? Studies have confirmed that coyotes dramatically affect white-tailed deer populations. Coyotes prey on deer fawns; thus fawn survival naturally is threatened by a large number of coyotes. The number of fawns and thus of adult deer is directly affected by the coyote’s diet and behavior.
The researchers of a northern Alabama study included Dr. Karl Miller[1] of the University of Georgia, Cory Van-Gilder[2], graduate of the University of Georgia, and Dr. Grant Woods[3], graduate of Missouri State University, University of Georgia, and Clemson University. The study focused on 2,000 acres where 22 coyotes and 10 bobcats were removed during fawning season. The result was a doubled deer fawn population.
Are Coyotes a Threat to Deer?
An increase in coyote populations results in a decrease in their preferred prey. During the booming fur industry, the southeast had no coyote packs and a high deer density. Now deer are scarce in some high-density locations previously having 50+ deer per square mile. The U.S. Government has to kill over 90,000 coyotes yearly because of stock predation.
Studies: Effect of Coyotes on Whitetail Deer Populations
Studies have confirmed that coyotes affect whitetail deer populations. The researchers of a northern Alabama study included Dr. Karl Miller[1] of the University of Georgia, Cory Van-Gilder[2], graduate of the University of Georgia, and Dr. Grant Woods[3], graduate of Missouri State University, University of Georgia, and Clemson University. The study focused on 2,000 acres where 22 coyotes and 10 bobcats were removed during fawning season. The result was a doubled fawn population.
Later, Miller went on to conduct a second study in Southwest Georgia on 2 sections of land. One section of 11,000 acres, 23 coyotes and 3 bobcats were trapped and on another 7,000 acres no trapping was done. The results were staggering. In the trapped area, 2 out of every 3 does had fawns. In contrast, in the un-trapped area only 1 out of 28 does had fawns.
Dr. John C. Kilgo[4] at the U.S. Forest Service at the Savannah River Site in South Carolina conducted one of the largest studies concerning the affects of coyotes on whitetail deer. Sixty fawns were collared and observed. Within the first 6 weeks, 73% (44) of the fawns died. Approximately 80% (35) were killed by coyotes, 13% (6) were killed by bobcat, and 7% (3) by unknown causes.
Dr. Kilgo’s Research on Deer without Collars
Dr. John C. Kilgo conducted another study on the adjoining land with deer having no collars. The researchers used only trail cameras to prove that the collars didn’t slow the fawns down. The mortality rate was the same.
Dr. Kilgo’s most recent studies disprove the theory that fawning cover will reduce the predation of fawns, finding the same results on land with less fawning cover.
Dr. Kilgo and Christopher Shaw of the U.S. Forestry Service tested the theory of “predator swamping.” With a balanced buck-to-doe ratio, all the fawns would drop at the same time. Kilgo and Shaw conducted a test on 2 tracts of land. On the first tract the deer had a high density and on the second tract a low density. Even though the land had roughly the same amount of coyotes, the rate of predation was roughly the same.
Effect of Coyotes on Deer: Additional Studies
In year 2005, Dr. Stephen Ditchkoff [5] of Auburn University and his students began collaring 50 fawns a year. When starting, they scarcely had a fawn killed by coyotes, but in 2008, they lost 34% of the fawns, and in 2009, over half.
Mark Buxton[6], a wildlife manager with Southeastern Wildlife Habitat Services in Thomaston Alabama, says at the QDMA’s annual convention in Louisville Kentucky “…food plots, timber stand improvements, and restoring native vegetation… can maximize their (the deer) potential. The coyote is the next big part of that equation.” Buxton says “if coyotes are not a problem on your hunting property they will be in a few years.”
Coyotes Target Fawns
Some would say the fawns were just at the wrong place at the wrong time. Buxton believes this is not the case. He trapped predators in 2009 during 3 months of spring and caught 20 coyotes and 15 bobcats from 1500 acres, beginning about a month before fawning begins. After 1 year, Buxton had caught 49 coyotes and continued into the 2010 fawning season trapping 14 more. In total, 54% of the coyotes trapped were caught during fawning season (34 of 63).
“That tells me when coyotes are targeting fawns,” Buxton states, “when fawns hit the ground, it’s game on for coyotes.”
Ditchkoff agrees, saying, “coyotes might have learned to identify doe behaviors that indicate fawns are nearby. That’s not unheard of. In Alaska, they’ve documented that when a cow moose acts in a way that indicates a calf is nearby, brown bears start a systematic search to find the calf. They just hammer moose calves.”
A Sharp Decline in Deer Population
During the late 1980s coyotes advanced into South Carolina, and by year 2006, the deer population had declined by 36%. Is this decline merely by chance, or is it the direct effect of coyotes preying on fawns and adult deer?
An in-depth study on Michigan’s Upper Peninsula indicated coyotes kill more grown deer and fawns than wolves, bears, or bobcat. For 3 consecutive years coyotes caught and killed more adult deer leaving their competition in the dust. Coyotes killed 7 deer, whereas wolves killed 3. Bears and bobcat trailed behind with 1 each. Coyotes were also the apex killing predator fawns with 22. Bobcats killed 12 and bears and wolves tied at 4.
In yet another study, Sarah Saalfeld[7], a student of Auburn University, under the direction of Dr. Stephen Dithckoff, found coyotes impacted deer in an urban environment the same as in the wild, contradictory to the expectation that cars would be the highest cause of mortality. Coyotes killed 67% of the fawns in an urban environment just as in rural environments.
It appears coyotes negatively influence deer populations. The elimination of coyotes has even doubled the survival of fawns in some cases. The removal of predators, especially coyotes, can significantly increase the deer population.
If deer in an area are scarce due to coyotes, hunters can help keep these fawn slayers in check. Trap and hunt them to help bring back a thriving deer herd, but be sure to check your states laws before you go out!
Hampton Harris
[1]Miller, Karl. The Coyote Factor – Taking a Bite Out of Deer
[2] Van-Gilder, Cory. The Coyote Factor – Taking a Bite Out of Deer
[3] Woods, Grant. The Coyote Factor – Taking a Bite Out of Deer
[4] Kilgo, John C. The Coyote Factor – Taking a Bite Out of Deer
[5] Ditchkoff, Stephen. How Coyotes Affect Deer Herds
[6] Buxton, Mark How Coyotes Affect Deer Herds
[7] Saafeld, Sarah The Coyote Factor – Taking a Bite Out of Deer
Mulligan, Don. Study Shows Coyotes Impacting Deer Populations
