Monitoring mammals in airfield environments; a case study of the Irish hare at Dublin Airport

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Ball, Samantha
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University College Cork
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The number of reported wildlife-aircraft collisions (i.e., strikes) with mammal species is increasing globally with severe consequences for passenger safety, industry economics and wildlife populations. Despite this, little research has been conducted on the class Mammalia in airfield environments, with strike mitigation research efforts predominantly focused on avian species. This thesis addresses some of the wildlife hazard issues faced by the aviation industry, specifically looking to mammal species. The thesis focuses on developing ecological survey methods for mammals in airfields and exploring the role of ecological data in informing strike risk. The Irish hare (Lepus timidus hibernicus) population at Dublin airport is used as a population case study to assess survey methods in an airport environment, throughout. As little is known about mammal strikes on a global scale, strike records with mammals from available literature and national aviation authorities are collated in chapter 1. These data highlighted that mammal strikes are widespread and identify 42 mammal families involved in strike events in 47 countries and demonstrate that reported mammal strike events have been increasing by up to 68% annually. Looking to mammal management measures on a European scale for chapter 2, the most successful mammal mitigation measures were identified as: (i) the management of watercourses within the airfield; (ii) the implementation of specific grass cutting regimes (94.4%) and (iii) the management of waste products at the airfield so as not to attract or sustain wildlife (93.8%). Utilising historical strike data in chapter 3, it was demonstrated that hare strikes have been increasing by an average of 14% annually at Dublin Airport with over 340 recorded wildlife strikes since 1997. The kinetic energy of such an event (10,576 J) is substantial enough to inflict damage to the landing gear of an aircraft, although this has never been reported to have occurred. As the basis of effective wildlife management practices necessitates reliable estimates of the population size, design and model-based distance sampling methods were compared, alongside Random Encounter Modelling, to establish ecological survey methods suitable for monitoring mammals in airfields for chapter 5. Population estimates ranged from 29 (SE ± 9) to 133 (SE ± 19) individuals, with the most robust model (nocturnal line transects), estimating a population size of 118 (SE ± 21) hares at Dublin Airport. A concern regarding mammal strike events is not only the strike event itself, but the secondary strike risk with a predatory or scavenger species. Camera trap surveys were utilised to identify secondary strike risk in chapter 4. It was identified that birds take an average of 2 hours and 23 minutes to detect a mammal carcass following a replicated strike event at Dublin Airport and an average of 11 hours 40 minutes for mammal species to detect a carcass. These data indicate that current clean-up practices at Dublin Airport (i.e., immediate clean-up and closing of the runway to facilitate clean-up operations) are likely adequate for reducing the likelihood of a secondary strike event. This thesis presents some of the first data collected through remote monitoring methods (camera traps/ GPS trackers) to inform of airside wildlife hazard. These methods, in addition to overlap analysis and cross correlation functions have demonstrated that recorded strike times are closely associated with hares’ circadian activity and largely dissociated with aircraft movements (chapter 6). Additionally, data collected via GPS tracking devices in chapter 7 demonstrated that the hares at Dublin Airport have an average home range size of 0.28 km2 (±SD 0.1 km2), based on 95% Kernal Density Utilisation Distribution. What’s more, it is demonstrated that the hares incorporate active area habitat types (i.e., runways and taxiways) into their home ranges with up to 13% of one individual’s movements incorporating these areas. These data have fed directly into the Wildlife Hazard Management Plan at Dublin Airport and instigated targeted strike mitigation measures. Throughout this thesis, the importance of ecological data for informing strike risk and mammal management in airfield environments is highlighted. While the Irish hare is used as a case study for ecological field methods in airfield environments, this thesis also broadly demonstrates the extent of mammal related issued at airfields worldwide. Thus, although here the focus is on a specific species at a specific airport, the developed methodologies are suitable for cohort of terrestrial mammals inhabiting airfield environments worldwide.
Airfield ecology , Wildlife strikes , Mammal strikes , Strike mitigation , Human-wildlife conflict , Wildlife hazard , Wildlife management
Ball, S. 2022. Monitoring mammals in airfield environments; a case study of the Irish hare at Dublin Airport. PhD Thesis, University College Cork.
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