IN FALL AND WINTER, deer can do a lot of damage to garden trees and shrubs–and those don’t recover so soon, if at all. Autumn seemed like prime time to get some help in minimizing the impact of deer in our landscapes from Marne Titchenell of Ohio State University, a wildlife program specialist in OSU’s College of Food, Agricultural, and Environmental Sciences.
First an anecdote: A recent September weekend, during a workshop in my garden, one attendee commented as he looked around at all the mature shrubs and big swaths of perennials: “You must have a fence, because otherwise this garden wouldn’t be here,” he said. Because it’s mostly hidden in the surrounding woodland tree line, he hadn’t spied the fence itself yet, but he just knew: It’s a deer-free zone.
A fence isn’t practical for every garden, but thankfully a range of other tactics are possible, from barriers that are less ambitious to erect, to repellents, to a smarter plant palette than I have and more. Marne shared various strategies in the October 10, 2016 edition of my public-radio show and podcast. Read along as you listen in, using the player below. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).
q&a: preventing deer damage with ohio state’s marne titchenell
Q. I know that “know thy enemy” is one of the prongs of success that you preach in wildlife control. Let’s start with getting to know the white-tailed deer, which east of the Rocky Mountains and actually most everywhere in the country except the Southwest, I believe, is the primary deer species In North America. Many animals haven’t done so well with human development, but why have deer done so well?
A. You’re right. First of all we’re talking about a very adaptive species. It doesn’t take them long to figure out the resources they need to survive and where to find those resources. They coexist with us very, very well.
What’s interesting about white-tailed deer, if you look back at their history in Ohio, for example, there was a time back in the early 1900s where there weren’t any deer—they were extirpated, which means they were no longer existing in an area they once occupied. A lot of that had to do with changing landscape and hunting pressures, but the point being that in 1923 they were introduced here, and only a short 20 years later, their populations had been doing well enough to allow hunting.
So this is a species that has a very successful reproductive strategy and is very good at finding the resources it needs to survive. When we look at Ohio, for example, there are great resources. When we look across the landscape, deer need a nice mix of open habitats as well as forested habitats, and we provide that.
When you look at the foods that they are eating, the Midwest is huge as far as agriculture and that provides a good food source for those deer.
Q. Oh, they do love those fields of food.
A. Oh, yes. And then when you start looking at our backyard, no matter if we’re urban or rural, whether we’re landscaping or gardening, we are providing food sources for deer. They capitalize on it.
Q. And it’s high-value food, too.
A. Very nutritious food, yes.
Q. I was reading about the white-tailed deer and its range, and saw a fact sheet from Texas where in the Texas Hill Country they claim more white tails than anywhere. It’s a very wide-ranging animal that succeeds in a lot of different areas. Here I am in New York State, in an agricultural area, and in the winter I can see in the cornfield across from me herds of 40 or 45 animals—that’s why I have that fence. [Laughter.]
A. There are definitely parts of Ohio that are experiencing the same kinds of deer pressure.
Q. And other areas as well, where listeners are located. Everyone says, “I’ve got deer.” How much do they eat? They seem like eating machines.
A. They are. They are the largest herbivore that we have in this part of the country, and they have to eat a lot of food to keep going—about 7 to 10 pounds of vegetation per day. They’re browsers, so they’re mostly focusing on leaves and buds and branches of mostly deciduous (but not always) trees.
They’re eating a lot of food. They’ve been documented as eating 500 different species of plants. They’re not picky, and they’re especially not picky when they are hungry.
Q. Does their diet differ by season? Of course there are different plants out there, but…
A. Yes, and that really dictates it: It’s what is available to them. Obviously during the spring and summer, they’re really focusing on that green vegetation. But once the growing season is over, and we go into fall and winter, they really focus on woody vegetation; they eat a lot of branches and bark. Though depending where they are, fruit from trees, such as acorns, can be a very important source for them as well.
But yes, they definitely do switch their diet depending what’s available.
Q. So now, let’s talk about sex, Marne. [Laughter.]
A. All right. [Laughter.]
Q. But really, it’s critical when trying to outsmart any animal, to understand its natural history and life cycle, and sex is a big part of it. And around this time, in the fall, some of the big damage can be done, especially to the woody plants—and all having to do with sex drive, I think.
A. You’re exactly right. This is perfect timing—here the breeding season starts in October, and goes through December and peaks in November. There are a lot of things going on at this time that does impact the amount of damage that we see.
Number 1, the breeding season known as rut often causes and increase in movement, especially in male deer, as they’re searching for females. You are going to see them moving out a little bit from their normal home ranges–so that could potentially increase the amount of damage.
They’re also increasing their food consumption this time of year, in preparation for winter. So that’s going to be a lot more pressure on food sources around our homes, as well as on natural food sources such as acorns.
Of course you have the males that are getting ready for the breeding season, polishing up those antlers to make them look all nice and shiny for the females. That’s when we start to see rubbing damage, and we’ve already seen some of that—sometimes it starts as early as August and lasts through September. That’s the males rubbing that velvet off their antlers in preparation for the breeding season.
What a lot of folks don’t know is that type of rubbing damage can continue through the breeding season—through December and sometimes into January. What’s going on there is the males have glands in their foreheads, and they will rub them on trees, leaving a scent mark, and that serves a communication, communicating their presence and their social status to other males in the area. So that is damage we can see continuing through the breeding season; lots going on.
Q. You brought a smile to my face when you were talking about the males being on the move looking for females. Last fall a male bull moose was walking down the road here—and if you’ve never seen one, that’s an insane-looking thing. Talk about big herbivores—it weighed some ridiculous amount like 700 pounds. [Laughter.]
A. I will never forget the first time I saw moose rubbing damage. It was like 8 or 9 feet up on the tree. [Laughter.] I thought, “Whoa, you don’t see that with deer.” It wasn’t that high up—but it was much higher than I am used to seeing with deer.
Q. If people have put in trees and shrubs, for example new fruit trees, this can be substantial damage—this is not nothing. And the animals are strong, really physical, pushing against the trees. Are the bucks polygamists?
A. Yes, and often when we talk about population management, we always stress focusing on the females, the one who reproduce. The males will mate with as many females as they can.
Q. He’s a man about town—and they have no natural predators.
A. Here in the Midwest, we got rid of the predators when we moved in—predators that would have helped us manage the deer population.
Q, So here we are, attempting agriculture or horticulture, and let’s talk about steps we can take. First we must correctly assess the damage and make sure we know who it is. How do we know it’s deer damage?
A. One of the things to really do is get down and look at the damage—look at what is left on the plants. You’re going to be looking for some jagged edges. That has to do with the deer’s dentition. They have bottom incisors but nothing on top, so they are going to grasp a plant and pull it, and that plant’s going to tear–no matter what part of the plant it is, leaf or branch. [Above, jagged edges on herbaceous plants; buck rubbing on tree trunks.]
So if you do see those jagged edges behind, and if you contrast that to something like rabbit damage, where they have those sharp incisors, it’s going to be very apparent in the difference.
You’re looking for that, and you’re also looking for where the damage is occurring. Keep in mind that deer are large animals, so they’re often going to be feeding from the top down or from the sides of larger shrubs.
If you’re having a lot of damage down near the ground, or from the ground up to about 2 feet, it could be rabbit. Observe where that damage is occurring, and what it looks like.
Q. Then you have reminded me when we have spoken previously that we have to create a toolbox—of tactical tools. We don’t just run willy-nilly around, trying different things, but we have to get serious and strategic. The toolbox has five dimensions—from lethal (like deer hunting), to exclusion, repellents, scare tactics and habitat modification. We can skip the subject of hunting and start with exclusion.
A. I talk about exclusion on two fronts—first is individual plant protection. That really applies when you’re coming into the fall and winter and the breeding season, when you have those antler rubs, that you protect your trees. You can use a tree shelter, which you can buy commercially, or you can use chicken wire to create a barrier around that tree, so deer can’t come up and rub that tree. That’s something we can implement.
Q. How high and low?
A. You want to go up at least 4 feet—4 to 5 feet tall. For shrubs and smaller plants like that, you can sometimes use netting to cover those trees. One gentleman said he used the mesh grid Christmas lights, and he placed it over one shrub, and that shrub didn’t suffer any damage, but all the other ones did. Just creating a barrier can really help to deter the animal.
So that’s individual plant protection. On a larger scale would be putting up a fence. They can be costly and time-consuming, so I really encourage folks to think about what it is that you are trying to protect. What is the value of those things, and can you turn around and really make that fence worth it?
Sometimes you can; sometimes you can’t.
Q. I’m a serious gardener; I have public open days and so on. It’s my profession. And it’s a couple of acres of garden, and there would be nothing there. I’m surrounded by a 5,000-acre state park, with giant herds of deer—so there was no choice. But there are sometimes choices—like if deer get into a vegetable garden in season, or if people have a particularly sensitive area like conifers that look tasty in winter, that they want to fence off.
What are some of the more DIY-ish inexpensive options? I saw your peanut-butter fence and so on.
A. The peanut-butter fence is excellent, and I will say right up front that it is an electric fence, and depending where you are there are codes and ordinances against those in some communities and cities. But if you’re able to do it, it’s great. It can be a simple one- or two-strand electric fence. It’s called the peanut-butter fence because you take a little bit of tin foil, you wrap it around the wire, and you put a little peanut butter on it. [Diagram from Internet Center for Wildlife Damage Management.]
What that does is it encourages the deer to touch its nose or tongue to that peanut butter in that foil strip, which is electrically charged, so they get that zap on a very vulnerable part. It does not cause permanent harm to the animal, but it will keep them away from that area. It’s a very simple fence; it’s not permanent. It can be put up and taken down even around small areas.
But even as far as non-electric fences, using plastic mesh or snow fence around smaller areas can be just as effective, using fence posts or rebar or whatever you have accessible. Just creating that barrier around those areas temporarily, like if you’re having high pressure in those areas coming into the winter.
Q. You can create a fenced-off area that’s temporary, DIY, and you can re-use the materials each year. With that peanut-butter fence you can do two strands, a low and a high—like 8 and 30 inches.
A. Yes, roughly, just to bolster that protection.
Another thing we should mention with fencing or any of these management options, is that you really have to have a good idea of your deer pressure. Are you sustaining a lot of damage, or not?
If you want to no question keep deer out, you want a fence to be 8 feet tall. I’m not staying you have to put an 8-foot fence to protect a small cluster of trees; you might get away with a 5-foot fence. It just depends on the deer pressure, and how dependent they are on the food source you are trying to protect.
Q. The needier they are, the more motivated they are to outsmart you and your fence.
So exclusion is the first tool—and it’s non-toxic, and either reusable or permanent. What’s the next tool?
A. Another one that I commonly talk about with homeowners would be repellents. That would be using a chemical—sometimes manmade, sometimes a naturally occurring chemical—and it is repelling the animal away, usually from a food source.
There are repellents that smell really bad, and repellents that taste really bad—and then there are some that do both. With deer the ones that seem to work best are ones that have eggs in them.
I encourage people when you’re looking for a deer repellent, pick it up, flip it over and look for that label, and that active ingredient. Look for eggs. Or the other ingredient would be hot pepper—which may be called capsaicin, which is just what makes hot peppers hot.
You’ll see a lot of commercially available repellents using both of those active ingredients. That’s because that’s what researchers are saying works best.
Q. With repellents, do the deer habituate to them—get used to them?
A. Yes.
Q. Because they have to taste it–like with the peanut-butter fence, they say, “Oh, I don’t want to do that again!” and that’s behavior modification. But in the case of putrescent egg solids or hot pepper, what happens?
A. It all goes back to what I said before: how heavy your deer pressure is, and how dependent they are on your food source. With repellents the general rule of thumb is that if you are sustaining a lot of deer damage, don’t waste your time with repellents. It’s either telling you that you have a lot of deer in your area, or they’re very dependent on your food source.
Usually repellent are best suited to light to moderate pressure from deer. Sometimes that’s just because there is another food source they can go to if yours tastes or smells bad.
Q. And repellents can add up cost-wise—you have to repeat the spray.
A. When you’re using and form of pesticide you want to read the label—and there is lots of good information in there. How often to reapply so it’s effective; if it’s rain-resistant or not. Definitely read that label and follow the instructions to be as effective as you can.
Q. There are some favorite plants—and of course there are listeners all over the country, so the desired plants vary—but Arborvitae, for instance, sounds like deer candy. Others?
A. There are lists out there of deer-resistant plants, and if you are having deer pressure, swapping out some of the more preferred, like Arborvitae, out for something less preferred, is another tool in the toolbox. And then incorporate repellents into your plan as well, especially when used on those less-palatable plants, where there is a higher success rate. [My page of links to regional lists of deer-resistant plants; above, a screenshot from a page in Rutgers’ search tool.]
Arborvitae is very popular, your fruit trees, Rhododendron, winter creeper—despite the number of plants deer do eat, they definitely prefer ones over others.
Q. You can at least make yourself at least a little less of a neon sign. [Laughter.]
A. Yes, be proactive—and if what you’re putting out there is attractive, that you’re going to have to shop for some repellents or another tool.
Q. One more thought: What really frightens me more than whether they eat someone’s backyard rose bush is that deer over-browsing influences forest regeneration, isn’t it?
A. It’s hard to wrap that up in a few seconds, because there is so much life in our forest understories. The food that is out there that the deer are eating, down to the forest floor, is a source for so many other vertebrates and invertebrates in our forests. Without that, they have huge impacts.
And then when you start talking about invasive plant species that are colonizing these disturbed areas—forests that are heavily impacted or browsed by deer can be perfect sites for invasive species. So it’s sort of a double whammy. Definitely a big issue.
more on deer and smaller animal control
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its seventh year in March 2016. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Oct. 10, 2016 show right here. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).
(Photos: Stripped bark off tree by Manfred Mielke, USDA Forest Service, Bugwood.org; buck in field by Scott Bauer, USDA Agricultural Research Service, Bugwood.org; buck rub by Joseph OBrien, USDA Forest Service, Bugwood.org; row of rubbed trees by David Mooter, Prairie Silvics, Inc., Bugwood.org)
