Application of Electrified Fladry to Decrease Risk of Livestock Depredations by Wolves (Canis lupus)

Lethal methods are important for predator management but new and innovative techniques may allow wildlife managers to reduce conflicts in ways that are most acceptable to the greatest number of people and optimize human-carnivore coexistence. Fladry is a suspended line of flagging used to exclude wolves from livestock; it has limited effectiveness because wolves habituate to the barrier. Electrified fladry is an extension of fladry, where flags are suspended from an electrified wire instead of a rope and designed to decrease the potential for wolves to habituate to the barrier. Using captive wolves I compared the effectiveness of fladry versus electrified fladry for protecting a food resource. Both fladry and electrified fladry effectively excluded wolves from a food resource for short durations of time (1-14 days). However, latency to cross and feed significantly differed between fladry (x̄ = 1.2 days, SE =0.2) and electrified fladry (x̄ = 4.6 days, SE = 0.5) (χ= 8.721, d.f. =1, P < 0.003). Caution should be used when evaluating mean survival time; electrified fladry mean survival times were underestimated because the largest observations were censored and the estimation was restricted to the largest event time. Our research also indicated that although electrified fladry has the potential to reduce wolf depredations, animal learning, motivation, and personality all influence effectiveness. 14 Introduction Wolf (Canis lupus) predation on livestock can cause economic adversity for livestock producers and can increase animosity towards wolves, thus complicating the balance of wolf conservation and other human interests. Predation management and conflict resolution between wolves and livestock producers has historically depended on lethal control (Knowlton et al. 1999). However, public support for lethal predator management has decreased (Mech 1996; Reiter et al. 1999) creating a strong need for alternative management strategies that help alleviate depredation pressure from wolves and minimize the need for reactive lethal management. Many non-lethal methods have been used in wolf management: translocations of depredating animals (Fritts et al. 1984; Bradley et al. 2005), using guard animals (Linhart et al. 1979; Green & Woodruff 1983; Cavalcanti 1997; Meadows & Knowlton 2000), scare devices (Shivik & Martin 2001; Shivik et al. 2003), physical and visual barriers (Gates et al. 1978; Nass & Theade 1988; Musiani & Visalberghi 2001; Musiani et al. 2003), and livestock husbandry (Robel et al. 1981). Some non-lethal techniques may be effective on a short-term basis, but additional testing and implementation of new methodologies in actual management situations is needed (Shivik 2006). Recent studies using the barrier technique known as fladry (flagging interspersed on a single strand of nylon twine) document that captive wolves avoided the flagging and thus access to food for short durations (Musiani & Visalberghi 2001; Musiani et al. 2003). Free-ranging predators also avoided fladry, which impedes wolves from crossing to access food for short time periods (Okarma 1993; Okarma & Jedrzejewski 1997; Musiani et al. 2003; Shivik et al. 2003). Because fladry is a primary repellent, it relies on 15 producing a flight or startle response to disrupt predatory behavior (Shivik et al. 2003; Shivik 2004). As with all primary repellents, fladry is rendered ineffective through the process of habituation, which results in an extinction of an animal’s fear of the novel object (Shivik et al. 2003). In the context of predator management, habituation to a novel object is determined by the intensity of a stimulus and the motivation of an animal (Shivik et al. 2003). Musiani and Visalberghi (2001) found that levels of excitement and motivation play a strong role in the habituation to fladry by wolves in captivity. Freeranging wolves that kill sporadically may be highly food motivated and habituate quickly to primary repellents such as fladry. Conversely, secondary repellents rely on conditioning using aversive stimuli in order to prevent a behavior (Shivik et al. 2003; Shivik 2004). Aversive conditioning can also be described as avoidance motivation, where flight behavior is initiated by discomfort, pain, or a general negative experience (Elliot & Covington 2001). Aversive conditioning using electric shock can prevent predation (Gates et al. 1978; Linhart et al. 1982; Nass & Theade 1988; Andelt et al. 1999; Huygens & Hayashi 1999; Poole & McKillop 2002; Breck et al. 2006), and a modification of the fladry design, electrified fladry, incorporates electrical stimuli. Electrified fladry is similar to fladry in that it consists of flagging; however, the nylon twine that supports flagging is replaced with an electrified wire (Gallagher Turbo-wire, North Kansas City, MO). Although the effectiveness of fladry is expected to decrease through time due to habituation, electrified fladry also relies on aversive conditioning to increase its effectiveness after habituation has begun. Poole and McKillop (2002) suggest that animals will investigate an electric fence or unfamiliar object by touching it with their nose, and thus by combining primary 16 and secondary repellents electrified fladry may at first frighten, and then condition wolves to avoid the barrier, therefore providing a better non-lethal tool. Thus, the objective of this research was to compare the effectiveness of fladry to electrified fladry in captivity to test the premise that reinforcing a primary repellent with a secondary repellent will create a more effective non-lethal tool. Methods I conducted controlled pen experiments during the winter of 2006 using 15 captive wolf groups at the Wildlife Science Center (WSC), Forest Lake, Minnesota under the National Wildlife Research Center’s Institutional Animal Care and Use Committee QA-1332. Specifically, I used 45 wolves, including 36 gray wolves (Canis lupus), 3 Mexican gray wolves (Canis lupus baileyii), and 6 red wolves (Canis rufus). All wolves were ≥ 1 years of age and were wild born or originated from previous wild captured wolves (Table 2.1). Wolf group sizes ranged from 1-7 animals and each group had its own enclosure (105m – 925 m chain-link fenced areas) that contained one 19 liter water bucket, 1-2 den boxes (2-5 m) and natural vegetation, including shrubs and trees. I assumed that all species and subspecies exhibited the same behavior, motivation, and predatory characteristics and would differ only in morphological characteristics. Throughout the study all wolves remained under the care of the WSC with no changes in animal husbandry (i.e. caretakers continued to feed, water, and clean pens as part of their normal scheduled activities). On a daily basis WSC personnel monitored wolves for injuries and alterations in physical condition and when required, physically restrained and immobilized wolves with approximately 3.3 mg/kg ketamine and 0.3 mg/kg xylazine (based on a 45 kg average weight of wolves). 17 Because it was difficult to distinguish individuals within a pack, I attempted to use 6.6 cm engravable band collars (Ritchey Manufacturing, Brighton, CO) with unique black symbols on a white background to identify individuals. Technicians physically restrained wolves using pin sticks and hand nets to place identification collars on wolves a week before the baseline data were collected. However, even with the collars, I was usually unable to identify specific individuals with the photography equipment I used. Thus, all analyses used the wolf group and not individuals as the sample unit. I collected baseline data for two weeks before treatments began to ensure pen familiarity and conditioning to novel objects (i.e. chained carcass and cameras). During baseline collection we placed passive infrared motion activated cameras (Reconyx RM30, Holmen, WI) on the outside of the pen fence, where they remained in place throughout all of the treatments. Cameras had a 40° field of view with a range of 18.3 meters from the camera, which covered the entire 8.5 m distance across the pen. I programmed cameras to take a series of photos at 4 frames per second upon activation. Barriers were monitored 24 hours a day (cameras were equipped with infrared illumination for night time use) and cameras recorded treatment information, time, and date of activation on every picture taken. I mounted cameras on the outside of the fence 1.2 meters high, and aimed them along the barrier line. Therefore, when a wolf approached the barrier, cameras recorded their behavior. I recorded average number of approaches per day, total number of approaches weighted by number of wolves, days fasted, and latency to cross barriers during two-week trials. I defined an approach as a single wolf occupying a location ≤ 2 meters from a barrier line in a single recorded photo 18 data image. Latency to cross was defined as the elapsed time between the start of trial to an event of a single wolf crossing the barrier line and freely feeding on the carcass. The food resource was one whole eviscerated road-killed white-tailed deer (Odocoileus virginianus) carcass previously collected in the surrounding area and was the normal maintenance food. I placed deer carcasses in the corner of the pen near the camera and chained them to the fence corner using 1.2 m of 0.47 cm stainless steel chain. To assign treatments, I randomly selected five pens to receive fladry barriers, five to receive electrified fladry barriers, and five to receive no barrier (controls). Trials were run in phases: Baseline, where all pens received tethered carcasses and no fladry barriers, Phase I, where 5 pens had fladry, 5 had electrified fladry, and 5 controls had no barriers, and Phase II when the treatments in fladry and electrified fladry pens were swapped, and controls remained with no barriers. Each pens’ trial lasted two weeks or until failure of the barrier. Failure was defined as one or more wolves crossing into the part of the pen with the carcass and freely consuming the food resource. For the fladry and electrified fladry treatments, I sectioned off an 18 m area within the pen by running the barrier from one side of the pen to the other. The fladry systems protecting the resource we constructed following the method of Musiani and Visalberghi (2001). That is, fladry and electrified fladry systems (Carol’s Creations, Arco, ID) consisted of red plastic flags (50 x10 cm) interspersed at 50 cm intervals on a 0.2 cm diameter blue nylon twine. I suspended the nylon twine 50 cm above the ground and attached it to fiberglass posts set at 3 meter intervals. During fabrication of the electrified fladry system, the nylon twine that typically held the flagging was replaced with a 0.2 cm electric mixed metal strand twine (Gallagher Turbo Wire, North Kansas, 19 MO) of nylon and wire. I suspended the electrified fladry from fiberglass posts in the same manner as the fladry. I suspended a second 0.2 cm electric ground wire (Gallagher Turbo Wire) 13 cm above the ground and attached it to the fiberglass posts. A 12-volt battery powered fence energizer (Gallagher B260) electrified the wire and produced a pulsed energy output of ≥ 2000 volts with 2.6J of stored energy and a resistance of 500 ohms. Three 1m copper rods grounded the circuit. The feeding protocol at the Wildlife Science Center used a randomized feeding schedule that provided food for wolves five out of seven days with varying portion size. I incorporated my testing into the feeding schedule and began trials after a 2 day fasting period. At the start of a trial, I placed a deer carcass at the most distant corner within the experimental area. A carcass remained in the protected area for 5 days; on days 6 and 7. I supplied carcasses in the unprotected area and replaced the carcass in the protected area. Statistical Analyses I analyzed the difference in latency to crossing events between treatments and made statistical comparisons between fladry and electrified fladry using the Wilcoxon signed-ranks tests and Kaplan-Meier survival estimator (SAS Institute, Inc, Cary, North Carolina, USA). To provide a more detailed representation of wolf behavior in relation to barriers and fasting, I also made descriptive comparisons of average approaches for overall trends by treatment and wolf group.