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Deer Exclusion Devices and Deterrent Techniques

EVALUATION OF THE EFFICACY OF VARIOUS DEER EXCLUSION DEVICES AND DETERRENT TECHNIQUES FOR USE AT AIRPORTS

1. Executive Summary

This document reviewed the various deer exclusion devices and deterrent techniques that are available to airport managers. It established that there has been a growing problem of compromised airport safety at many North American airports as populations of white-tailed deer have grown. Deer behaviour and airport location often results in deer interfering with aircraft operations, causing delays and deer strikes to aircraft during takeoffs and landings. The goal of this report is to provide an evaluation of existing deer control methods to assist airport operators in reaching the target of "zero tolerance" to deer at airports.

Methods to control deer were reviewed from world-wide literature, proceedings of wildlife control conferences, communication with wildlife workers, including airport managers, game farm owners and staff at public zoos. The relatively small literature base concerning deer control at airports was augmented by studies to control deer in agricultural, residential and highway traffic situations. A variety of devices and techniques were compared for their appropriate use at airports and recommendations were made based on effectiveness of design, suitability, duration of control, maintenance requirements and implementation requirements by airport managers. Manufacturer claims of performance were largely ignored, but manufacturer documentation was used for determining product specifications and methods of application. Independent scientific literature was considered to provide the most reliable and accurate source of objective information. Reliable estimation of costs were often not available for many deer control methods due to lack of documentation, the exclusion of personnel costs and installation costs, the area and topography of application and/or the old age of many literature sources.

Effective perimeter fencing is the most important component of a successful deer control program. This can be enhanced by habitat modification to remove vegetation on and around airports to reduce their attractiveness and discourage deer from entering perimeter fences. A variety of electric and non-electric fences were compared to determine their effectiveness.

Effective electric fence designs rely on a combination of height and number of electric lines that administer a rapidly pulsed charge of 4,000 to 5,000 VDC. They provide about 80% exclusion of deer that attempt to cross the fence by conditioning them to associate electric shocks with the fence. This effectiveness declines when (1) maintenance is inconsistent; (2) when lines are short-circuited by weed growth or snow cover; or (3) when deer are highly motivated to cross the fence when populations are high, during the rutting season in the fall, or when frightened by hunters. The ElectroBraidT Deer Fence is recommended. The cost of an ElectroBraidT fence installation in 1999 was about $8,960/km, including all materials and installation costs. Vertical High-Tensile Electric Fence designs with a height of 1.8 m or more have limited recommendation due to difficulties experienced by a number of airports when maintenance lapsed and deer populations were high. Costs for Vertical High-Tensile Electric Fence designs were difficult to determine, but they were estimated to be about $7,700/km. Deer were found to enter airport properties soon after current was interrupted by damage. Other electric fence designs were not recommended due to reduced performance and winter durability problems.

Effective non-electric fence designs rely on height and adequate coverage of any gaps under the fence that could permit deer to cross the fence. Standard 2.44-m Chain-link Fencing that is topped with barbed wire and has a total height of 3.0 m provides about 95% exclusion of deer at an approximate cost of $43,000/km. Taller versions of chain-link deer fencing (3.7 m) offer better exclusion (about 98%), but at a higher cost. A 2.44-m Fixed-Knot High-Tensile Fence topped with three strands of smooth high-tensile wire to increase the fence height to 3-m. offers an equivalent effectiveness to chain-link fencing at a cost of approximately $30,000/km. The 3.7-m tall version of this fence offers still higher protection. Polypropylene deer fencing, such as Tenax® Heavy Duty Perimeter Fence, has limited recommendation due to lack of information available from sources outside of the manufacturer, suppliers and installers. It offers an inexpensive alternative to other types of fencing, but it cannot be fully recommended until it is evaluated independently. Other types of non-electric fences, such as Sloped or Slanted Steel Mesh Fencing, are not recommended due to their insufficient height to exclude deer. The effectiveness of perimeter fencing can be improved by excluding deer from entering at gates that must be left open for vehicle traffic with the use of cattle gates.

When fences do not provide complete exclusion of deer, either due to design limitations or fence damage, deer must be removed from the enclosed area. This can be done by a variety of means. One-way gates, deer jump ramps and deer leaps are passive methods that can be incorporated into a perimeter fence. Other methods involve removal by using dart guns, drives and live traps and re-location. Shooting with live ammunition may be necessary in some situations. Relocation is far more costly than shooting, but when the social climate prevents the use of lethal means, capture and relocation may be necessary. Permits to remove and/or kill deer involve participation with the provincial natural resources ministry and all federal gun control laws must be followed.

For short-term control, a number of deer deterrent techniques can be used to frighten deer from airport runways. Pyrotechnics are recommended for short-term control if used by trained personnel to ensure good presentation of the explosive charge. Gas Cannons and "Exploders" can be used to frighten deer from local areas if only fired when a deer is close by. Otherwise, deer will habituate to them readily. The use of shotguns with live ammunition to scare deer is not recommended unless the local deer population is actively hunted. Success of these techniques has been variable and will need to be replaced with permanent methods such as fences when deer habituate to them. All other noisemaking methods including Av-Alarm and Ultrasonic devices, are not recommended. Visual deterrents such as flashing lights and reflectors are not recommended. Hazing with aircraft to disperse deer from an airfield is not recommended. Natural and artificial chemical repellents are not recommended for use at airports.

Control of the local deer population through the use of legal seasonal deer hunting is an effective means of reducing the frequency of intrusion of deer into airports where it can be permitted.

Infrared early warning devices currently being developed by defence contractors with the U.S. military have potential to alert airport operators of wildlife hazards that would interfere with airport operations. Initial costs have been high, but these systems promise to be valuable components of future wildlife control programs at major airports.

The effective implementation of suitable combinations of the current recommended techniques and devices by skilled wildlife control personnel is capable of significantly reducing the risk of deer interference and strikes at airports.

Date modified:
2010-05-03