Managing Problem Deer Populations

As the snow starts to fall, deer start congregating in wintering grounds and actively seek high energy sources of food for survival. Dormant apple trees with both healthy fruit buds and new shoot growth provide an excellent food source during the winter months. Anyone who drives or lives in southern Ontario is aware that deer sightings have increased. In the U.S., the national deer population is estimated to be 25 million to 30 million. Deer have become well adapted to living in environments near suburbia, and they have benefited from warmer winters and a decline in hunting in some areas. Deer prefer fragmented habitat that consists of both woodland for cover and open crop land. The USDA estimates that total deer damage from auto collisions and crop and timber losses reaches at least $1 billion a year (Mullen, 2002).

Deer damage to young non-bearing and mature apple trees can be troublesome. Smaller more compact apple trees in higher density plantings make a greater proportion of the tree canopy available for browsing by deer. Feeding on soft tender shoot tips and terminal growth as well as fruit buds in winter and early spring often results in an acute reduction in bearing surface, and changes in tree shape. Smaller trees can be damaged or destroyed by rubbing of antlers to remove velvet, in a process called ‘horning’. This type of injury is usually seen in orchards from September to mid-November. Controlling deer damage in orchards can work where an integrated approach is used, which includes regulated hunting (with authorization), scare devices, repellents and fencing (conventional and electric). For a given deer density, the potential for economic damage can be often greater on large plantings than on small ones, as a result large areas often require more substantial fencing designs to achieve a level of protection similar to small areas. Nursery trees in large blocks can require exclusion fencing to ensure recovery of quality nursery stock if there are large herds in proximity to these young trees.

Fencing

There are several different types of fences available, including woven wire fence, which is an excellent option for areas where deer densities are high and the likelihood of damage is great. The permanent woven wire fence provides a barrier that requires little maintenance but can be expensive to install. The costs of these fences often limit their use around orchards, with the exception of nurseries. The 8 ft high, vertical fence is constructed from two 4 ft sections of 6 X 12 inch wire mesh, joined with hog rings. Two or more strands of barbed wire spaced 10 inches apart are added to the top of the structure extending the overall height to 10 ft or more. Based on research in New York, blocks larger than 50 acres usually require this type of fencing to reliably prevent deer from entering the area if feeding pressure is high.

Invisible fencing

Another type of fence is mesh fencing. This fence is considered to be strong, long lasting, virtually invisible and easy to install. The fence is made of a series of 4-inch square UV resistant polyethylene mesh. Each strand has a breaking strength of 175 lb. The mesh is stretched 20 ft between poles that can be used to support it. The entire area that needs to be protected must be enclosed in order for the fencing to be effective. This fencing is considered to be very effective because deer have relatively poor vision and depth perception. The barrier and accessories are black in colour so the deer can not judge where the fence starts or stops. They fear the fence and will run around its perimeter but will generally not challenge it vertically. This fence provides a humane and discreet barrier that keeps deer out of sensitive areas without relying on chemicals or electricity.

High-tensile electric fence

This fencing has emerged as the preferred method to exclude deer from orchards in New England. These fences are easy to erect, repair and maintain. In addition, the high voltage low impedance chargers can electrify long fence lines (up to 5000 ft or more). Temporary electrified fences are simple, inexpensive and useful. Baiting the fence with peanut butter, apples etc. may enhance the effectiveness of electrified fences. Deer are attracted to these fences by appearance or smell and are lured into contacting the fence with their noses. The shock trains the deer to avoid the fenced area. Permanent high tensile electric fences provide year round protection from deer and are best suited to orchard crops. In New York they consider these designs to be best used under light deer pressure or for relatively small areas. Low profile fences seldom provide satisfactory protection of commercial orchards in the winter especially if snow restricts deer from using alternative food sources. Landowners must check local ordinances to determine if electric fences can be used on their property.

Scare devices

Frightening deer using scare devices may be effective and economical in some situations, particularly when they first become a problem in the orchard. However, once deer establish a pattern of movement it is difficult to get them to change. Propane cannons, cap exploders, strobe light, sirens, fire works and gunfire can be used as a temporary method of scaring off deer. However, deer often become accustomed to them within a week or two, even when the devices are occasionally moved. Scare devices are usually a short-term solution. Some growers use dogs to help scare deer. Dogs are kept behind an ‘invisible fence’ using a radio transmitter, an underground copper wire and a special dog collar with receivers. Dogs are placed inside the fence, and the dogs chase the deer out of their territory. If they attempt to pass the invisible fence they receive a mild harmless shock. Be aware that a family pet may not provide adequate protection because it is not patrolling all the time. Often large aggressive dogs work best.

Repellents

There are two types of repellents that can be used for deer. They are contact and area repellents. Contact repellents are applied to the plants and repel by taste. Area repellents are those used most commonly in orchards and are applied near the plants to be protected and repel deer by smell alone. Some area repellents include suspending bars of hand soap to the trees or hanging bags of human hair from the tree. Some growers have reported that the use of Surround Crop Protectant containing kaolin clay acts as a deterrent to deer feeding while getting trees established. Unfortunately these repellents may only be a temporary solution to the problem.

Hunting

During the hunting season, problem deer in orchards can be hunted by licensed hunters. Agricultural deer removal authorization is another way of managing deer populations. Applications can be obtained from the Ministry of Natural Resources (MNR) to hunt outside of the normal sport hunting season. These permits can be used to harass and/or remove deer that are causing significant agricultural damage, when other reasonable methods to prevent damage are ineffective. Only those animals that are damaging crops can be removed. Orchardists may apply for an agricultural deer removal permit through their local MNR district office. Applicants are normally required to document and describe all other non-destructive attempts to control a damaging population of deer. Applicants must meet certain criteria and a site visit is usually completed. Authorizations are closely controlled and complement local deer management objectives. Deer removal authorizations can not be used to provide recreational out of season hunting opportunities or personal gain.