Do coyotes cause deer declines?

2CoyotesB&W

Coyotes kill deer.  This fact is undisputed.  The real question is:

Do coyotes cause deer populations to decline?

This question has led to years of research.  While there are still strong advocates on both sides, enough science has been done that there is an evidence based answer to this question.

Coyotes will scavenge deer carcasses any time of the year (1) and usually have deer hair in their scat, but they primarily hunt deer during the spring and the winter in areas with snow.  There is some evidence of coyotes hunting adult deer in areas without snow, but this is not well documented.  Studies from northern areas show during mild winters coyotes kill less deer and switch to other prey like snowshoe hare(2), and it is hard for coyotes to kill adult deer without snow to slow and exhaust deer.  It is mainly the alpha male and female of territorial breeding pairs that kill deer and livestock, and younger and transient animals stick to smaller prey and scavenging (3).  In fact the presence of the alpha pair is just as important for deer hunting success as the coyote pack size(4).

In the spring coyotes focus on hunting deer fawns, and in areas without wolves or bears coyotes are usually the largest source of fawn mortality.  In various studies coyotes have caused fawn mortality as high as 50% and as low as 9% (5, 6).

Killing lots of fawns means that coyotes are bad for deer right?  Unfortunately it is not that simple.  There are two main kinds of predation, compensatory and additive predation.  Compensatory predation describes a situation where a predator kills prey that would have died from other causes later in the year (i.e. starved to death) while additive predation are predator kills that add to the total mortality rate (i.e.  predators kill healthy deer that would have survived the winter).  The real question is whether coyote deer kills are additive or compensatory.  If predation is additive than coyotes are lowering the deer population, but if most predation is compensatory than coyotes are only killing deer that would die from something else.

One way to figure out which kind of predation is happening is to shoot a bunch of coyotes in one place and not shoot them in another place and look at the difference in fawn survival (some researchers build a fence and then shoot the coyotes).  Many early coyote removal studies removed coyotes in the spring and then counted the ratio of fawns to does in the fall (7).   These studies showed that coyote removals increased the number of fawns that survive to the fall, BUT they did not follow fawn survival through the winter and we don’t know if those fawns survived to become adult deer.

Researchers saw the problem with these studies and conducted some very large and intensivecoyote deer research throughout the United States.  A 9 year study in Idaho removed both mountain lions and coyotes(8) and several large studies in Wyoming, Utah, and Colorado removed coyotes from areas ranging from 40 to 300 square miles(911).  None of these studies found any evidence that coyote removal caused an increase in the deer population.  The study in Idaho actually found that fawn predation was more affected by the abundance of other prey than coyote removal.   The two best coyote removal studies with white-tailed deer populations also show that coyote removal does not affect overall population growth.  The first study in southeast Texas showed that coyote removal increased fawn survival but did not change the population density(12).  Another long term study of a deer population in a predator free fenced area in Texas found that deer density increased for a few years and then sharply declined to match the populations outside the predator exclosure (13) and the deer in the predator free area had a much poorer diet (14).  The researchers concluded that coyotes actually had a stabilizing effect on the deer herd.

The fact that coyotes are not causing deer populations to decline can also be seen in the effect white-tailed deer are having on forest ecosystems throughout the eastern United States.  Overabundant white-tailed deer have been shown to decrease tree regeneration (15), changed the composition of the entire plant community within reach of a feeding deer (16), and changed shrubs enough to decrease survival and abundance of nesting songbirds (17).

Do coyotes cause deer declines?

The evidence says no.  There is no evidence that coyotes are the factor that keeps deer populations from growing and actually evidence that some predation may keep the deer herd from overshooting the food supply.  Agree or disagree?  Leave a comment below, but please be civil.

4 coyotes

Literature Cited

1. M. Bekoff, Canis latrans, Mammalian species , 1–9 (1977).

2. B. R. Patterson, L. K. Benjamin, F. Messier, Prey switching and feeding habits of eastern coyotes in relation to snowshoe hare and white-tailed deer densities, Can. J. Zool. 76, 1885–1897 (1998).

3. B. N. Sacks, J. C. C. Neale, FORAGING STRATEGY OF A GENERALIST PREDATOR TOWARD A SPECIAL PREY: COYOTE PREDATION ON SHEEP, Ecological Applications 12, 299–306 (2002).

4. M. Elbroch, K. Rinehart, Behavior of North American Mammals (Houghton Mifflin Harcourt Trade & Reference Publishers, 2011).

5. W. B. Ballard, D. Lutz, T. W. Keegan, L. H. Carpenter, J. C. deVos, Deer-Predator Relationships: A Review of Recent North American Studies with Emphasis on Mule and Black-Tailed Deer, Wildlife Society Bulletin 29, 99–115 (2001).

6. W. B. Ballard, H. A. Whitlaw, S. J. Young, R. A. Jenkins, G. J. Forbes, Predation and Survival of White-Tailed Deer Fawns in Northcentral New Brunswick, The Journal of Wildlife Management 63, 574–579 (1999).

7. G. G. Stout, Effects of Coyote Reduction on White-Tailed Deer Productivity on Fort Sill, Oklahoma, Wildlife Society Bulletin 10, 329–332 (1982).

8. M. A. Hurley et al., Demographic response of mule deer to experimental reduction of coyotes and mountain lions in southeastern Idaho, Wildlife Monographs 178, 1–33 (2011).

9. J. L. Harrington, M. R. Conover, Does Removing Coyotes for Livestock Protection Benefit Free-Ranging Ungulates?, Journal of Wildlife Management 71, 1555–1560 (2007).

10. D. E. Brown, thesis, Utah State University.

11. R. M. Bartmann, G. C. White, L. H. Carpenter, Compensatory Mortality in a Colorado Mule Deer Population, Wildlife Monographs , 3–39 (1992).

12. S. L. Beasom, in Transactions of the North American Wildlife and Natural Resources Conference, (1974), vol. 39, pp. 230–240.

13. J. G. Teer et al., in Transactions of the North American Wildlife and Natural Resources Conference, (1991), vol. 56, pp. 550–560.

14. J. G. Kie, D. L. Drawe, G. Scott, Changes in Diet and Nutrition with Increased Herd Size in Texas White-Tailed Deer, Journal of Range Management 33, 28–34 (1980).

15. D. M. Waller, W. S. Alverson, The White-Tailed Deer: A Keystone Herbivore, Wildlife Society Bulletin 25, 217–226 (1997).

16. T. P. Rooney, D. M. Waller, Direct and indirect effects of white-tailed deer in forest ecosystems, Forest Ecology and Management 181, 165–176 (2003).

17. D. S. deCalesta, Effect of White-Tailed Deer on Songbirds within Managed Forests in Pennsylvania, The Journal of Wildlife Management 58, 711–718 (1994).

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24 responses to “Do coyotes cause deer declines?

  1. It would make sense that coyote predation would have a positive effect of stabilizing deer populations, even if they didn’t make them go up or down. My question is what does a large deep population do for coyote population. A larger deer population means more fawns and more sick/exhausted adults for coyotes to feed upon, and one would imagine this would result in larger coyote populations. Any thoughts on that?

    • Sorry for the delay in reply David, things have been very busy here finishing up the fall camera trapping season. A large deer population may cause an increase in coyote populations but maybe not. Coyotes are eating fawns when they are raising pups of their own, so lots of fawns might mean that the pups are well fed and that more survive to become coyotes and cause a population increase. There is also research that shows that in many places with abundant rabbits fawns are not the preferred food of coyotes and coyotes will eat more rabbits unless the rabbit population is on the downswing. Here in the east there are not that many rabbits and lots of deer, so coyotes eat plenty of fawns. This probably helps the coyote population stay stable at least, but whether it causes an increase is hard to say.

  2. Thanks for the summary! As a bow hunter, I prefer to harvest does because I believe the population is out of balance due to lack of predation and trophy buck hunting (in Wisconsin anyway). I’m tired of hearing fellow hunters shooting coyotes from their stands, justifying it as “protecting the deer herd”. To not even use the killed coyote is unethical, but I feel my thoughts on the matter are ignored. Your article helped support my case. Thank you!

    • I hunt in Taylor County, Wisconsin of course. I’m on the fence with the entire idea. One the one hand coyotes keep a balance making sure the strong live on and the week don’t go to waste. But then again imagine no coyote or predators at all, you would without a doubt have some huge deer running around. Sure some will die in pain so a quick kill from a coyotes would be beneficial in helping keep the healthy, healthy. if there where no predators period the deer population will thrive, it’s been proven especially down south with no hard winters. I remember when I would see 50-60 deer in a day hunting Waupaca County in Wisconsin, no because of predators you see few. The population was healthy back then and is still healthy today as in no sick deer just fewer due to predation. Long story short, coyotes have a direct impact on deer numbers, to say anything else means you hunt in an area that isn’t been plagued with coyotes. So, when the day comes you have see nothing but coyotes instead of deer, you might change your mind.

  3. Do coyote’s cause deer herd’s to decline? The answer would have to be yes. There can be no other answer, unless you use the kind of math say like our government. If a coyote eats one buck then that herd has declined by one member. If same coyote eats a doe then the herd declines by one plus all the offspring she would of had.
    If we were dealing with only deer and coyote interaction it would not be such a big deal. However we are not in Georgia. We have cars, hunters, EHD, poachers, bad management from our own DNR, and various other issues. When you factor in animal that targets fawns in the spring then you have trouble. I started hunting deer in the late seventies and it was great to see one or two deer on stand for the whole season. I mainly hunt N. Georgia where the numbers aren’t as high per square mile. During the eighties and nineties you could see deer most every day. Now along with our DNR regulations and coyotes we are fast heading toward single digits per season again.
    There are many factors involved,and I am aware of them,but to me it is the coyote that has been the hidden factor. The last few years I have seen more fawn less does than I can remember. Before coyotes moved into our area I routinely saw does with twin fawns, now that is a rarity. So to end this rant it is obvious to me that coyotes are to blame.

    • Thanks for your comments Jeff. Coyotes definitely kill deer, and you are correct that if a coyote eats a doe than the herd declines by one plus her future offspring. The good thing for deer is that coyotes don’t eat that many does, especially in places like Georgia where there is no snow to slow deer down so coyotes can attack and kill them. Coyotes do eat a lot of fawns, but the question is whether the fawns that coyotes eat would have survived or if they would have died anyway from something else. Our article says that in every study where they have shot all the coyotes, fawns die from something else and the deer herd does not grow, and this has happened over and over again.

      There are studies going on right now in the east where coyotes have been increasing, and it will be interesting to see what they find.

      • Thank you for responding. All it can go on is what occurs every fall in my area that I deer hunt. It used to be a rarity to see a doe ,without a fawn or two trailing behind her, in the fall. It was not uncommon to see her with two fawns . Now it is rare to see her with two fawns, and the last couple of years, I see more does with no fawns.
        We have stopped shooting does for this very reason. It is legal for us to take up to ten does ,where I hunt, a season, but we are not seeing the numbers that would allow us to do that. It is very discouraging to see healthy does with no fawns.
        I understand that their could be other factors at play here, but the most obvious reason a perfectly healthy looking doe has no fawn is because of the coyotes in our area.
        Now ,in conclusion, I believe that a animal that kills 50% of the fawns in an area will cause a decline on the deer herd in an area that is hunted. Before coyotes arrived in our area very few barren does,after coyotes lots of barren does. What is killing the fawns logic says coyotes. Half the fawns are does and if they kill them when they are fawns they are still dead.

    • Supply and demand…Most predator/prey ecosystems have direct correlations between populations…from my observations it is more ethical to allow these beautiful animals to hunt and prey on the sick and injured ( mostly from bad arrow placement ) and keep the remaining population healthy and strong…I don’t know what the fawn mortality rate this winter will be in Maine, but I bet it was high. There we’re a lot of fawns that made it through the summer and with the cold winter and limited wintering grounds and food, many suffered and eventually died anyways.

  4. It has been a pleasure to volunteer with eMammal for the past two seasons. Documenting coyotes was one of the most interesting parts of the project we were involved with (and there were many)! Just in the studies we did in our area in Maryland, combined with actual camera sets, interviews with DNR and National Park personel and actual reports from hunters and landowners, we documented an over abundance of Coyotes and Deer in certain areas. There seems to be a direct correlation in the “over- populated” deer areas to having also an over abundance of Coyotes. In one area there is an over population of both! I have no doubt that the Coyotes take advantage of carcasses as well as prey heavily on the deer herds, yet the over population of the deer seems to just “enable” the coyote population- where the coyotes are devestating livestock and everything else in the area more than the deer. Despite the heavy coyote population in this area, the deer herd seems to grow out of control if left unchecked by other means. Thanks again for this article and the great experience and opportunity!

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  6. Great breakdown. I was discussing this topic with a family member over the weekend, my uncle is considering coyote hunting based on the assumption they are curtailing deer populations here in Colorado. I pointed out that USDA’s Wildlife Services killed 75,000+ coyotes in 2013, and likely similar numbers in past years, which doesn’t appear to be solving anything, except potentially protecting livestock. It’s nice to see a science based article regarding this issue, i’m going to send others this way.

  7. Upstate New York has an overabundance of deer. The dead deer by the side of the road proves this. To kill off coyotes by huge numbers is not the answer. Coyotes also eat rodents that carry the plague and hanta virus. The deer near my moms home ate all her grapes and other produce. To protect deer and fawns is not the answer most people want to hear. My husband and I have hit deer with our cars alot of money went into fixing cars. My car was totaled. We need a balanced ecosystem. Hunters need to understand deer are overpopulated in some areas. Coyotes can help with deer over populations every day of the year.

  8. In the West coyotes are blamed for mule deer decline and are hunted down or trapped in the cruelest ways. Never do you hear about the impact on deer from the thousands of cattle grazing on public and private lands and competition for forage, or road kill on frequently traveled highways, or human encroachment into mule deer territory via urban sprawl, or disruption of migration byways, or even disease. As far as I am concerned it is a manmade, ignorant scheme to kill for the sake of killing. Over 7,000 coyotes murdered this year in Utah. When rabbits, ground squirrels and zillions of other rodents overrun the state, then we will hear a whine to the farthest reaches of deer country.

  9. Hey thank your very mutch for this great article. I am a forestry student from Germany and I am asking myself if a wolf or lynx population had the same effect on european red deer populations as the american coyotes have on the american deer ?

    I dont recognize any serious european researche to this topic…

    Best regards,

    Julian

  10. Don’t believe all the propaganda coyotes can and do decimate deer and turkey populations. If you’re an Auto insurance company or farmer it works out for you . If you’re a hunter or a deer or turkey it stinks. I spoke with people from PA in back in the 90’s and coyotes were decimating they’re turkey populations back then and putting a nice dent in their deer populations at least in the areas these people lived. In NJ I spoke with someone who has a trail cam on a den site that 5 or 6 coyotes use, they brought back 72 deer carcasses in a year, that’s right 72. They’re silent killers working mostly at night, just because you don’t see them or here them a lot doesn’t mean they’re not there. If you notice a steep decline in deer and turkey populations in your area the coyote is the main suspect. As far as taking an adult deer no problem, I’ve seen a pair in full pursuit of adult deer. The eastern coyote is part timber wolf and sometimes much larger especially in the head and jaw area they prefer bigger game but will hunt anything. You can see a video of coyotes taking down a large whitetail buck on YouTube, there’s no snow on the ground and it doesn’t seem they had to much of a problem.

    • Thanks for the comment John. It is definitely possible for coyotes to kill adult deer, but to influence population dynamics they must do that on a regular basis. We claimed there is little evidence for coyotes killing adult deer regularly. Coyotes bringing 72 carcasses to a den site is impressive, although the counting method will influence the number of “carcasses” (e.g. do you count all the deer legs and divide by 4 or count every large chunk of dead animal as a carcass when it might be several pieces from the same deer?). However, that many carcasses may mean that coyotes are really good at scavenging roadkill, since NJ is a high roadkill area, or it may mean that coyotes are killing a lot of deer. Finally, many eastern coyotes do have some amount of wolf DNA and are larger on average than western coyotes, but the size difference is not enough to change them from small mammal hunters to full time deer killers.

  11. This article is bias and does not reference the studys performed recently in the southeast. In this region, the coyotes have migrated further south and are dramatically reducing fawn survival rates. Consequently, areas with low deer populations due to droughts have had no chance to recover. Do not rely on this article to make judgement.

    Also, whenever you see words like BUT capitalized in an article, understand that the author is attempting to sway judgement. This is an editorial and not true journalism.

    • Thanks for commenting on the article. Do you have any reference information about the recent studies you mention from the Southeast? We provide several pieces of evidence to support that coyotes do not cause large declines in deer populations, but we are always open to new evidence.

  12. As land owner in upstate new york and being an avid outdoorsman I have seen the decline of deer in the last ten years. I believe part of this is that hunters that don’t report there kills ,and the rise of the coyote populations.I have seen the kills of fawns on my property. the 2014 deer season i bought my license and after two weeks of watching what herd i had i decided not to hunt. We are seeing a loss of all our wild life and measures should be taking
    Bob Smith
    Coventry New York

  13. I hunt a large piece of woods in new Jersey and have been hearing a large number of cyotes nearby. I’ve been hearing them all summer aND now I hear them sitting in my stand. It sounds to be at least a pack of six of them, probably more though. last year I took a deer with my bow, the deer ran 60 yards and stopped. As soon as the deer stopped two cyotes howled and they were not very far away. This is when I knew I was going to have a problem. Last year I did alot of run hunting and would see alot of deer in groups of 8. I would see different groups of deer, as to where I didn’t know what way to look because they were all over. now this year on the other hand I have hunted these same locations and am aware that deer can change there movement patterns and locations. I now only see one or two deer every time I sit. I’m not 100% but I think that this has to do with these damn Coyotes. it’s very stressful knowing that the population of deer has grown since I was younger due to my family and I letting more deer walking by rather than taking them. and now very quickly my time spent sitting is alot less interesting because I would really enjoy just seeing deer walk through. these cyotes have either done alot of damage or have chased the deer off to another area. since there are few deer now I guess I will have to start hunting these bastards instead. I’m afraid to shoot a deer because I feel like they’re endangered in my area. I really hope that in the near future I have an exiting hunt so I can believe these cyotes didn’t ruin my hunting location which was prime whitetail country swamp with oakridges. sorry for the improper Grammer, and for ramBaling, I wrote this on my cell phone. I just wanted to let it be known that these cyotes no good from my perspective. they aren’t helping anything and I think the state brought them here. when I started hunting the amount to be harvested was unlimited basically now the fees to hunt cost hundreds of dollars, bag limit decreased, and so did population. I wish they would’ve just let hunters take care of this and not bring them here. unless this happened naturally but who knows because what the government does and what they say they do are two different things.

  14. Why else would our government (ODNR in my home state of Ohio) have a NO closed season or a No bag limit, if their research, studies etc, proves that they are “over harvesting” deer turkey and other wildlife?

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