CAPTURE OF MOOSE WITH FENTANYL AND XYLAZINE

CAPTURE OF MOOSE WITH FENTANYL AND XYLAZINE J. C. HAIGH, Department of Veterinary Clinical Studies, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon R. R. STEWART, Department of Tourism and Renewable Resources, Fisheries and Wildlife Branch, Saskatoon R. FROKJER and T. HAUGE, Alberta Oil Sands Environmental Research Program, Rochester Research Centre, Rochester, Alberta Ab6t~aet: A brief summary of chemical immobilization of moose in North America is made. This looks at the various methods of approach, and the weapons and drugs used. Most data available on successful moose capture refer to either succinylcholine chloride or etorphine hydrochloride. Preliminary results on a combination of fentanyl citrate and xylazine hydrochloride used for the immobilization of 47 moose are given. The animals were darted from a helicopter with Cap-Chur projectile syringes fired from the extra long-range projector. A dosage between 0.14 mg and 0.53 mg/kg of fentanyl and 0.15 to 0.53 mg/kg of xylazine provided satisfactory immobilization. Hyaluronidase was added to the mixture on 24 occasions. This had the effect of reducing the induction time between 36 and 45 percent. The injection site was also found to effect the speed of induction injections over the heavy muscle masses of shoulder and hind limb producing more rapid immobilization than in other sites. A major factor in successful moose capture from a helicopter was the experience or lack thereof of the pilot in this type of work. During the course of telemetry studies by biologists in Alberta and Saskatchewan, the use of a mixture of fentanyla and xylazine b as an immobilizing agent was investigated. Simultaneously investigated was the use of the enzyme hyaluronidase c which had been used to shorten induction times in succinylcholine immobilized animals (Literature cited 6.). Apart from the tagging of moose in water (24.,26.) or deep snow which has permitted the insertion of eartags and on occasion radio collars, a b c Fentanyl Citrate. McNiel Laboratories, Don Mills, Ontario, Canada. Xylazine hydrochloride (Rompun). Bayvet Haver-Lockhart Laboratories, Shawnee, Kansas, U.S.A. Wydase. Wyeth Ltd., Toronto, Ontario, Canada. 107

studies of moose have involved the use of several different chemical agents. Chemical immobilization permits the collection of a variety of data, including body measurements, weights, and tooth, blood, and fecal samples. Such capture implies that the target animal has been approached within range of a syringe projector. This has been accomplished by a variety of means, including trapping (6.,14.,16.,17.,18.,25.), running into deep snow with dogs or stalking, firing from a truck (2.,14.,22.), and darting from a helicopter (5.,6.,20.). Of these, trapping and the helicopter are the most commonly reported methods. In some instances, work with traps has proved less than satisfactory with high mortality rates probably associated with shock (17.,25.). However, at the Kenai Moose Research Centre over 2,000 moose have been trapped. Total mortality was less than 3 percent (8.). The method does not involve large expense apart from initial construction costs which will vary depending upon the trap site. Traps do not have a high yield. Darting from a helicopter has many advantages over other techniques. The machine not only acts as a vehicle for the dart-gun but as a tool for efficient search. In areas of low moose density, a helicopter has been used in conjunction with a fixed-wing aircraft used for initial search in order to cut down search times from the more expensive helicopter (Hauge, Haigh, and Keith, Unpublished data). The 2 main groups of drugs that have been used are the neuromuscular blocking agents and the analgesic narcotics. If one examines the desirable properties of an immobilizing drug (21.), it can be seen that the most popular of the neuromuscular blocking agents, succinylcholine, lacks 1 essential property - that of reversibility. The drug has a variety of other disadvantages which include a low therapeutic index, variable activity according to both individual animals and season (4.,14.), short duration of activity, and failure to suppress conscious central nervous system activity. The psychological stress placed on an animal that is unable to take any action in the face of infringement of both its flight and attack distances by man must be considerable. The only saving grace may be the rapid 108

metabolism of the drug in animal tissues which would permit consumption of carcasses by hunters soon after an animal had been darted (15.). Reported mortalities associated with its use have varied from 2 to 26 percent (2.,5., 14.) Etorphine hydrochloride d has been the narcotic in use for animal capture in Africa for many years (11.), and is now widely used for moose capture on this continent. Disadvantages associated with etorphine include high cost, the fact that it is a narcotic under strict Dangerous Drug classification, and the unexplored area of tissue residues and potential human health hazards to hunters following animal capture. Etorphine has wide therapeutic index which varies from species to species but may be in excess of 9,000 (1.). The drug is readily reversible and should the need arise, 'booster' doses can be given. Immobilization of African species in excess of 6 hours by this method have been reported without adverse effects (13.) Other drugs have been used, including nicotine sulfate, phenycyclidine hydrochloride e, C1744 f, and xylazine with varying success. None has proved entirely satisfactory (5.,22.). Following numerous reports of the synergism displayed between narcotics and xylazine (11.,12.,21.), recent reports indicate that these combinations have excellent properties for moose immobilization. In Alaska adult moose are caught with a combination of etorphine and xylazine (7.). In Alberta a dose of 6 mg etorphine and 100 mg xylazine has proven effective for adult moose (Hauge, Haigh, and Keith, Unpublished data). Thanks are due to Dr. A. W. Franzmann and G. M. Lynch for reviewing the manuscript. MATERIALS AND METHODS Moose were captured by dart immobilization. The moose were, in most d e f M99 - D-M Pharmaceuticals Inc., Rockville, Maryland, U.S.A. Sernylan. Parke-Davis & Co., Ann Arbor, Michigan, U.S.A. C1744. Parke-Davis & Co., Ann Arbor, Michigan, U.S.A. 109

cases, spotted, herded, and darted from either a Bell Jet Ranger or a Hughes 500 helicopter. At Fort McMurray in areas of low moose density, animals were spotted from a fixed-wing aircraft which was able to call the helicopter to the appropriate spot. Because the Cap-Chur long-range CO 2 powered projector has proved unsatisfactory in extremes of climate (22.), the Cap-Chur extra long-range dart projector was used with green low power charges and syringes of 3, 5, and 7 ml capacity. The darts were pushed down the barrel of the gun with a piece of 3/8 inch dowl to a predetermined position. This provided a flat dart trajectory at ranges up to 12 m, and reduced muzzle velocity and consequently impact speed of the dart. DRUGS Fentanyl Fentanyl is a short rapidly-acting narcotic extensively used in animal capture and restraint (21.). Its actions are similar to etorphine and can be readily reversed. Outside the small animal field the drug has not been widely investigated in North America apart from 1 report in a review of the use of this drug which gives dosage data in zoo animals and in some North American species (12.). Fentanyl was used at solution strengths of 40 and 30 mg/ml. Xylazine Xylazine, although effective when used alone in immobilizing doses in moose, induces a long-lasting state of immobility (5.,6.). Treated animals require constant supervision to prevent them from falling into lateral recumbency and so possibly developing ruminal tympany. In some species, xylazine has not proved to be an effective immobilizing agent and in most the lengthy effect of an immobilizing dose is at best time consuming (5.,6.,9.). When used at doses ranging from 1/2 to 1/10 of the immobilizing dose in conjunction with narcotics, xylazine has considerable application in the field of chemical restraint (7.,11.,12.). Not only does xylazine overcome many of the signs of excitation during narcotic induction, it also acts synergistically in lowering the dose of narcotic required. Induction times may thereby be shortened. Care must be exercised not to use too much xylazine 110

in such mixtures as the residual effects of the xylazine could endanger animals especially in the face of predation once the effect of narcotics in the mixture has been antagonized. Xylazine was used at 300 mg/ml. Hyaluronidase Hyaluronidase was used in 24 instances in drug mixtures in order to determine whether the drug had any effect on shortening induction time in animals treated with fentanyl-xylazine mixtures. This drug is available in solutions containing 150 N.F. units/mi. It was added to darts either at 150, 225, or 300 N.F. units/dart. No weights of animals are available to enable doses to be given in mg/kg. The animals are therefore divided into calves of the year and others. The sample size is insufficient to allow statistical analysis of effective doses between males and females, but doses of drugs used in animal immobilization are often expressed in terms of animal weight rather than sex (21.). Rough estimates of weights in this study can be made relative to known moose weights, especially as many of the animals were caught within 113 km (70 mil of the only study made (3.), and were all of the subspecies ande~~oni. Records were made from the time of sighting a target animal. These included length of hazing, duration of intense chase, time of darting, injection site, onset of signs of ataxia, time to stopping, and time to recumbency. If the animal was physically restrained prior to becoming recumbent, this was marked as the "down time". Samples taken during moose processing included hair, blood, fecal, incisor teeth, and body measurements. The analgesic antagonists investigated were naloxone hydrochloride g used at 5 and 10 mg/ml, and levallorphan tartrate h used at 10 and 20 mg/ml. These were given by the intravenous route just after a small (25 percent of IV dose) intramuscular dose. g h Narcan. Lorfan. Endo Laboratories, Mount Royal, Quebec, Canada. Hoffman-LaRoche, Vaudreuil, Quebec, Canada. III

RESULTS Flying In Saskatchewan in an area with a moose population density of 0.56/km 2 (1.46/mi 2 ), 18 moose were immobilized in just over 9 hours of flying time. A similar figure of approximately 2 moose/hour was obtained in Alberta in an area with a moose density of 0.77/km 2 (2/mi 2 ). Both these results were obtained with helicopter pilots experienced in this type of work. With inexperienced pilots the figure rose to 1 animal/l.5 hours. Using both fixed-wing aircraft and helicopter in an area with a moose density of 0.22/km 2 (0.58/mi 2 ), 5 animals were captured in 2.5 helicopter hours and 3 fixed-wing hours. Without the assistance of the fixed-wing aircraft, the helicopter hours per moose in this area were more than doubled. Drugs A combination of fentanyl and xylazine has been used on over 40 moose. Fentanyl proved safe and effective at doses varying from approximately 0.14 mg/kg to at least 0.53 mg/kg in conjunction with xylazine doses ranging from 0.15 to 0.53 mg/kg. At the lower dose (47 mg fentanyl and 50 mg xylazine in 1 March-captured yearling bull of approximately 330 kg) induction was lengthy (24 minutes) and the animal had to be physically restrained. At the upper dose (200 mg fentanyl and 200 mg xylazine in a 3 1/2-year-old bull of approximately 375 kg) induction occurred in 3 minutes after the 2nd dart. Throughout the handling period, the heart and respiratory rates remained within acceptable limits. The heart rate was 50 and the respiratory rate 12/minute, 7 minutes after the animal became recumbent. Five minutes later the heart rate was the same and the respiratory rate had risen to 18/minute. No attempt had been made to investigate the upper limits of safety with the drug in moose. The results are shown in Table 1. The table shows the induction time from injection of animals darted in heavy muscle masses where drug absorption is likely to have been optimal. The animals are divided into calves of the year and others, and an estimation of weight is given. 112 It is also divided

Table 1. Induction times in fentanyl/rompun captured moose with or without added wydase. Good injection site (A) + Wydase No wydase Calves Moderate injection si te (M) No wydase Good injection site (A) + Wydase No wycase Adults Moderate injection si te (M) + Wydase No wydase Number Mean induction time (min) 5.40 8.75 7.5 4.92 8.90 9.67 14.83...... w Range Percent decrease in induction time (3-9.5) (3-19) 39% (7-8) (2.5-7) (6-15) 45% (7-12) (10-24) 35%

into those animals which were injected with a mixture to which the enzyme hyaluronidase had been added and those to which it had not. The addition of hyaluronidase decreased the induction time between 36 and 45 percent. The table also shows those animals in which injection occurred over less well-muscled areas, such as the flank or posterior rib cage. Induction times, both with and without the addition of hyaluronidase, are markedly longer than in those animals injected in optimal sites. In 3 instances, darts placed over these areas (Fig. 1 'M') produced either mild ataxia or no visible effect. Clinical Signs During the course of handling of the animals, temperature, pulse, and respirations were monitored. Handling times varied from 11 to 61 minutes (mean 21 minutes). Temperatures were taken as soon as possible after the animal went down and as near the end of handling as possible. There was no significant difference between these temperatures (P> 0.05, ~24 = 1.00296). Initially they varied from 37.1 o C to 4l.2 o C (mean 39.4 o C). At the end of handling the range was from 37.5 0 C to 40.6 o C (mean 39.5 0 C). Pulse rates ranged from 30-110 (mean 58 beats/minute, n = 46). Respiratory rates ranged from 12-40/minute (mean 27.7, n = 47). Analgesic Antagonists Of the analgesic antagonists, intravenous doses of naloxone varied from 0.025 to 0.10 mg/kg. One mg of naloxone antagonized from 3 to 12 mg of fentanyl (mean 5.3, n = 34). In the case of levallorphan, the doses given by intravenous route varied from 0.15 to 0.25 mg/kg. One mg of levallorphan antagonized from 1.2 to 3.0 mg of fentanyl (mean 1.62, n = 10). LOSSES No deaths attributable to drug effects were recorded. Two cases of confirmed capture myopathy which developed soon after capture, and 1 other death which occurred some days following capture and may also have been from the same cause, were recorded. One other animal was seen lying down 24 hours after capture. It rose when approached on foot but was noticeably lame. 114

DISCUSSION A critical factor during the capture of these moose was the experience or lack thereof of the helicopter pilot. On days in which an inexperienced pilot did the flying, the air hours per moose increased greatly and the time of harassment of individual moose was increased with potential detrimental effects to the moose. Considerable co-ordination between helicopter pilot and dart-gunner is required. In order to reduce the chance of missing the target, the aircraft must be flying at the same speed as the animal is running, while neither descending or ascending. An ideal position which allows the pilot to see both the target and possible obstructions is above, to 1 side of., and slightly behind the animal. This allows maximum chance for darts to be placed in areas of heavy muscle (Fig. 1, areas shaded and marked 'A'). Darts placed over the posterior half of the thorax (Fig. 1, stippled and marked 'M') will often also function efficiently. Darts placed in areas marked 'Z' will seldom cause immobilization, although some degrees of ataxia may be observed in animals in which partial absorption occurs. Similar discrepancies in the efficiency of immobilization by darts related to injection site have been noted in both moose (6.) and other species (4.,10.). In Alaska, hyaluronidase has been shown to have a definite effect in shortening the time of induction in immobilization with succinylcholine (5., 6.). Indications from the current study are that the induction time in fentanyl/xylazine mixtures is at least as much effected by the addition of hyaluronidase. The numbers of animals were insufficient to permit meaningful statistical analysis. Similarly the injection site of the dart appeared to be important in reducing the induction time. Mean temperatures (n = 24) of 39.4 o C are considerably lower than those recorded in other moose immobilized with narcotics and correspond with those in hand-held calves (24.). In moose captured with etorphine, extremes of body temperature (up to 42.S o C and 43.3 0 C) have been noted (19.,23.). In these 2 studies the mean temperatures measured were 40.SoC (n = 3S) and 4l.3 0 C (n = 22). us

Fig. 1. Potential dart injection sites: A. Areas over heavy muscle masses giving good chances of drug absorption. M. Posterior thorasic and abdominal areas from which drug absorption may be delayed or prevented. z. Areas in which successful darting is unlikely. 116

In moose captured in traps and immobilized with etorphine, respiratory rates varied from 18 to 128/minute (mean 56.3, n 42) and heart rates from 56 to 152/minute (mean 95.7, n ~ 34) (19.). It is not possible to assess whether the drug or the different type of stress provided by the helicopter as opposed to traps was influential in producing the substantially lower figures for all 3 parameters in this study. However in Alaska, the etorphine/xylazine mixture, apart from enhancing tranquility both during induction and after narcotic reversal, eliminated the problem of overheating seen in moose immobilized with etorphine alone (7.). LITERATURE CITED 1. Alford, B.T., R.L. Burkhart, and W.P. Johnson. 1974. Etorphine and diprenorphine as immobilizing and reversing agents in captive and free-ranging mammals. J.A.V.M.A. 164:702-705. 2. Bergerud, A.T., A. Butt, H.L. Russell, and H. Whalen. 1964. Immobilization of Newfoundland caribou and moose with sudcinylcholine chloride and Cap-Chur equipment." J. Wildl. Manage. 28:49-53. 3. Blood, D.A., J.R. McGillis, and A.L. Lovaas. 1967. Weights and measurement of moose in Elk Island National Park, Alberta. Can. Field Nat. 81:263-269. 4. Edebes, H. 1969. Notes on the immobilization of gemsbok (04yx gazeiia gazeiia) in South West Africa using etorphine hydrochloride (M 99 ). Madoqua Ser. 1:35-45. 5. Franzmann, A.W., P.O. Arneson, R.E. LeResche, and J.E. Davis. 1974. 6. Development and testing of new techniques for moose management. Prog. Rep. Alaska Fish Game. J. Zoo Anim. Med. 5:26-32. Job 1974. Immobilization of Alaskan moose. 7.. 1976. Evaluation and testing techniques for moose management. Job Prog. Rep. Alaska Fish Game. 8. 1977. Personal communication. 9. Grootenhuis, J.G., L. Karstad, and S.A. Drevemo. 1976. Experience with drugs for capture and restraint of wildebeest, impala, eland, and hartebeest in Kenya. J. Wildl. Dis. 12:435-443. 10. Harthoorn, A.M. 1971. The capture and restraint of wild animals in Soma, ed. textbook of veterinary anesthesia. Company, Baltimore. Pages 404-437. The Williams and Wilkins 11.. 1976. The chemical capture of animals. Balliere Tindall, London. 117

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