Wildlife in Airport Environments: Preventing Animal–Aircraft Collisions through Science-Based Management

5: Excluding Mammals from Airports

To ensure aircraft safety, it is critical to exclude large mammal species such as deer (Odocoileus spp.), feral swine (Sus scrofa), and coyotes (Canis latrans) from airport environments, as well as to consider thoroughly and carefully all available management methods. Airports are often located on or adjacent to undeveloped land that provides habitat for various species large enough to pose a direct hazard to aircraft. Unoccupied expanses of forage near runways provide deer with sufficient incentive to leave cover and occupy airport lands. Associated risk and tragic collisions have ranked deer as the most hazardous wildlife group to aviation (Dolbeer et al. 2000, DeVault et al. 2011), necessitating the evaluation of appropriate means for excluding them and other medium to large mammals (Dolbeer et al. 2000). Exclusionary fences are the most effective, long-lasting, and straightforward tool for eliminating risks posed by deer and other large mammals at airports; however , these fences can be costly to purchase, erect, and maintain. Fences provide a visual sense of security for airport managers but also can accomplish a measurable and statistically significant level of protection to aircraft at airports (DeVault et al. 2008). A variety of evaluations and experiments have been conducted on fence options. Determining the most appropriate fence for a specific setting to accomplish a desired outcome can be challenging. When reviewing this body of literature, airport managers must consider the level of motivation among deer or other species in the experiment and relate it to their situation. In this chapter we review a variety of fence applications for excluding medium to large mammals and provide recommendations. Federal Aviation Administration Recommendations The Federal Aviation Administration (FAA) prepares and circulates advisories on recommended practices to airport operators and safety inspectors. Since 2000, the FAA has disseminated three particular advisories, called CertAlerts, related to fencing strategies for deer (see http://www.faa.gov/airports/airport_safety/certalerts/). The first (No. 01-01; Castellano 2001) established minimum fence standards for excluding deer from airports. Standards specified chain-link fence at least 2.4 m (8 feet) high with 0.6-m (2-foot) outriggers with an unspeci fied number of strands of barbed wire. Recommendations specify that the fence must also be buried a minimum of 0.6 m (2 feet) and monitored daily. In 2004, recommendations were revised to specify a 3.0-m (10-foot) chain-link fence topped with three strands of barbed wire and a 1.2-m (4-foot) skirt buried in the ground at a 45° angle on the outside of the fence (Castellano 2004). Research results compiled by the National Wildlife Research Center, which is part of the U.S. Department of Agriculture, Wildlife Services program, prompted the release of CertAlert No. 02-09, stating that alternative electric-fence designs (1.2–1.8 m [4–6 feet] high, 5–9 strands) proved 99% effective in stopping deer Kurt C. VerCauteren Michael Lavelle Thomas W. Seamans Excluding Mammals from Airports 5 50 wildlife management techniques and could be suitable in limited, though unspecified, situations at airports (Castellano 2002). In 2004, an additional CertAlert was released that included all of the above information but specified that gates in fence lines must provide no more than a 15.2-cm (6-inch) gap that could potentially allow access by deer (Castellano 2004). Minimum recommendations provided in the CertAlerts for chain-link fences are appropriate when land managers must virtually eliminate access by medium to large mammals, realizing there is always potential for a break in a fence to occur by uncontrollable causes. Deer-Strike Statistics From 1990 through 2009, the FAA received 964 reports of deer–aircraft collisions (i.e., deer strikes)— including white-tailed deer (O. virginianus; 879), mule deer (O. hemionus; 55), and generic “deer” of undetermined species (30)—with 84% of the strikes resulting in damage (Dolbeer et al. 2011). Reported cost of the strikes was $31.7 million (http://wildlife-mitigation .tc.faa.gov/wildlife/database.aspx). Coyotes are an additional wildlife hazard, resulting in 321 strikes, 22% of which having an adverse effect on aircraft and 9% causing damage (Dolbeer et al. 2011). As populations of deer and feral swine continue to increase (Côté et al. 2004, Ditchkoff and West 2007, respectively) the threat of strikes increases, mandating the exclusion of these mammals from airports. Physical Abilities When attempting to exclude or contain an animal, its size, intelligence, and physical ability must be considered (Fitzwater 1972). There are...