by Sally Colby
Nearly everyone who grows a crop outdoors has encountered problems with deer damage. When populations of large natural predators (wolves and big cats) were high, deer populations were kept in check. With the loss of such predators and less natural habitat, deer have become bold as they seek habitat and food. While hunting helps manage deer populations, the loss of habitat and the ability of deer to adapt to changing conditions makes it more difficult to manage them.
If the deer population remained in balance with sufficient carrying capacity in areas with ample wild food, deer probably wouldn’t venture out of those areas. But that isn’t the case, and deer have increasingly significant economic impact on orchards, Christmas trees, horticultural crops and field crops.
Deer cause damage to crops in many ways, including browsing on vegetation, trampling, rubbing and stripping bark. The first step in combatting deer problems is understanding their habits and recognizing signs of deer presence. Become familiar with the habits of deer, especially those in your area, and look for more than hoof marks and scat. Spend some time this winter tracking deer to learn their habits in your area.
As prey animals, deer are hard-wired to be on the lookout for threats to their well-being, including unusual movement. Deer are typically afraid of anything strange or new, but quickly adapt to that which remains the same. When deer become accustomed to an area and feel relatively unthreatened, they are likely to return regularly.
Deer are browsers and prefer young vegetation up to about five feet. However, hungry deer will browse on whatever they can reach standing on their hind legs. Deer are creatures of habit, and if they discover a feeding area where their safety isn’t threatened, they will continue to return. Deer prefer to spend time at the edge of wooded and brushy areas that provide cover. Any fields with landscape trees, Christmas trees, horticultural crops and orchards adjacent to wooded and brushy areas are ideal deer feeding areas.
Changing the appearance of habitat can help deter deer. When possible, leave open space between field edges and crop material. Clearing underbrush and maintaining a wide swath of (at least 60 feet) reduces safe cover for deer and encourages them to rest and seek food elsewhere.
Like other ruminants, deer lack upper front teeth (incisors). In place of teeth, deer have a dental pad which they use in combination with lower incisors to tear vegetation, which leaves rough edges on plant material. Deer prefer young growth and remove leaves, buds and shoots – all of which affect the upcoming crop and tree growth. Deer browsing often results in girdling of young trees.
Deer develop eating habits that can be difficult to change. Any time a deer feeds or rubs in an area without unpleasant consequences, the behavior is reinforced. The key is to break the feeding habit, convince deer to eat and rub in a different area, then remain vigilant to deer attempting to return. Deer tend to become quite persistent in areas where they’ve successfully eaten, so the key is preventing them from developing a taste for what you’re growing.
Most deer herds don’t travel far and tend to eat in one area and rest nearby. Deer that move into orchards or other crop areas to feed will move back to cover to rest. During hunting season, deer are more active at night. It’s important to pay attention to signs of deer presence/damage throughout the year to understand their habits. Game cameras are relatively inexpensive and can provide valuable insight about deer habits on your farm.
Managing deer requires an IPM approach and may include hunting, barriers, repellants, scare tactics and vegetation management. The kind of damage being done and when damage is most likely to occur will help to determine which deterrents will be most effective.
Locate any deer paths leading to the growing area and place physical barriers (a rock base with logs or brush piled on top) to dissuade deer from using that path. When deer are forced to use a different route, they tend to break up and move more erratically, which is a change in behavior that can lead to exclusion.
Like other prey animals, deer eyes are on the sides of their heads, which means they have poor depth perception. Some growers have successfully used three-dimensional electric fences that make it difficult for deer to judge the height and width of the fence.
Frightening deer to discourage them from inhabiting or feeding in an area works best as a short-term solution because deer quickly become accustomed to the sounds. Any sounds should be set to go off at irregular intervals, and the sound source should be moved frequently. Some growers use dogs contained in invisible fence to deter deer, but be aware that GAP rules disallow dogs in growing areas.
Upright deer fencing is one of the most effective means of keeping deer out of crops. Adult deer can easily jump seven feet or higher and can work their way through small gaps in fencing. Effective deer fencing is usually eight feet or taller. Keep in mind that deer are normally fearful of new situations and can jump quite high from a standstill. Design a fence to allow a wide barrier (six to eight feet), cleared area that provides an escape route for deer, which is easier than jumping over or attempting to crawl under a fence they encounter.
An electric fence can help deter deer, but it takes some planning to create effective fencing. Once the fence is up, put peanut butter on strips of foil and hang it from the wires to entice deer to touch the electric fence with their sensitive mouths. Be sure the fence is on – deer can quickly learn to feel the electric pulse and can easily tell when it isn’t on. Leave the fence on 24/7 when it’s first installed, and if it’s turned off during the day at some point, be sure to keep it on at night.
When searching for new food sources, deer use their sensitive mouths and noses, so it’s important that any electric deterrent is strong enough to work. Deer hair is hollow, providing them with higher resistance to electricity, so it’s important to use a sufficiently powerful energizer for electric fencing.
While it’s probably impossible to completely eliminate deer damage with anything other than a secure eight-foot perimeter fence, decide what you’re willing to invest to protect your crop and make decisions about deterring deer based on economics.