The author would like to thank the Center for Environmental education for its valuable support in the preparation of this document and presentation of these findings, and acknowledge the cooperation of the Argentine Society for the Protection of Animals Delegation of Mar del Plata, and the Friends of the Earth Argentina.
Abstract
In recent years, South American sea lions (Otaria flavescens) and southern elephant seals (Mirounga leonina) in Argentina have beers observed to be entangled in discarded fishing gear and other man-made wastes.
This study describes a new method for the capture and rescue of entangled pinnipeds that was tested at the nesting colony of the South American sea lion Otaria flavescens in Mar del Plata Harbor, Province of Buenos Aires, Argentina, in May and June of 1983, and April of 1986.
Animals were captured using tranquilizer darts shot through a blowgun. Hoops of plastic, rope and metal were then removed from their necks. Thirty-two animals were chemically injected using varying dosages of Promacine, Ketamine, Xilicine and Hyaluronidase. Darts with buoys attached for Pursuing animals in the water were also tested.
The study includes a discussion of the results and the utility of the applied methodology in the rescue of entangled South American sea lions 0. flavescens.
Introduction
Numerous cases of pinniped entanglement have beers reported in the southwest Atlantic. Payne (1979), and Bouner and McCann (1982) reported that Arctic fur seals (Arctocephalus gazeus) from the southern Georgia Islands were entangled with hoops of synthetic cord and synthetic packing tape. In recent years, investigators have seen South American sea lions 0. flavescens and southern elephant seals (M. leonina) from colonies in continental Argentina affected by this same problem.
The present study was conducted in Mar del Plata, in the Province of Buenos Aires, Argentina, during the months of May and June of 1983, and April of 1986. A colony of South American sea lions (0. flavescens) has established itself at this location only within the last thirty years and is made up predominantly of subadult and adult males. The number of female animals in this colony is very low.
Some animals had plastic packing hoops entangled around their necks which varied from loose to extremely tight, and sometimes lacerated the muscle tissue.
Materials and Methods
Study animals were injected with immobilizing drugs by means of projectile syringes which were shot through a blowgun designed by the author. The blowgun was constructed from an aluminum tube, polished on the inside and covered with black plastic on the outside. Blowguns of 1.20 m and 1.70 m were used. To achieve a better trajectory, the darts were equipped with a stabilizing vane made of synthetic yarn. Projectile syringes with a capacity of 3.5 cc and 7 cc were used, equipped with needles of 1.5 x 50 min, and 1.5 x 80 mm.
The tranquilizing drugs used included: Promacine Chlorhydrate 50 mg/ml (1), Ketamine Base 100 mg/ml (2), Hydrochloride of Xilazine 100, 150, and 200 mg/ml (3), and Hyaluronidase (4).
1. Esparinal, John Wyeth Laboratories, Division Veterinaria de Nutricion Animal, Buenos Aires, Argentina.
2. Irnalgene. Estrella Merieus S.A. Buenos Aires, Argentina.
3. Rompun, Bayer Argentina S.A. Division Veterinaria, Buenos Aires, Argentina.
4. UNIDASA, Roux-Ocefa S.A., Buenos Aires, Argentina.
Dosages were based on the estimated weights of the study animals. Assessment of the weight of each animal was done by visual inspection, as there is no reference in the literature of any method for estimating pinniped weight using body measurements. Weights for the study animals were classified into one of five categories: 100, 150, 200, 250, and 300 kq, with a margin of error of 50kg. All the animals injected were sub-adult and adult males.
The hypodermic darts were shot into the zone above the hip, in the area of the longissimus dorsi. When it was riot possible to use the hip, the shoulder was used. In these two zones of the body, 80mm needles were utilized.
Buoy darts were constructed to be used for those cases in which it would be necessary to follow the animal through the water. The buoy darts had a 2 to 5 in. thread attached to their synthetic yarn with a small, brightly-colored balloon attached to the and. Flanged needles were used to keep the buoy darts from falling out of the animal's flesh.
Attempts were made to avoid disturbing the animals. Visual, acoustic and tactile stimula were minimized or, when possible, eliminated, and necessary movements were made outside the visual field of the animals.
Healthy, unentangled specimens were also injected to evaluate the effect of the drugs (except in the case of the Promacine).
The ambient temperature averaged 13 degrees centigrade during field work.
In order to quantify the effectiveness of the drugs, the following observations were made: the degree of muscle coordination, resistance to manipulation, loss of corneal reflexes, response to small stones that were thrown at the resting animal, and reaction to a needle pricked on the skin.
The degree of immobilization was arbitrarily divided into five categories based on the resistance to manipulation, degree of coordination, and muscular tone; 0 - The animal shows no visible effects. Active resistance to manipulation.
1. The animal is capable of moving, but with a loss of coordination.
2. The animal is not capable of locomotion, but capable of swimming. Capable of performing strong, but uncoordinated movement. The animal can be manipulated. but it is risky because the animal is alert, sensitive and able to bite.
3. The animal is capable of sporadically performing gentle movements of the neck and limbs. Loss of superficial sensitivity. Sporadically it develops resistance to manipulation. It has the capacity to bite just for an instant.
4. The animal is unable to perform movements, exhibits loss of superficial sensitivity, and is totally limp.
5. Same as 4, and without reflexes.
Results
During the three rescue operations, 32 animals with hoops around their necks were seen, one with a rope, two which had wire hoops, and the rest had from one to five plastic hoops similar to those used to hind crates of fish for exportation. The plastic hoops could be observed ranging from loose to extremely tight, sometimes cutting the epithelial arid subcutaneous tissues, and at times lacerating the muscle tissue. Hoops were less conspicuous when they were very tight. The advanced stages of tightening apparently interferes with feeding, since the hoop compresses the esophagus. Weight loss was evident in those animals with very tight hoops.
Three entangled animals each weighing 250 kg were injected with Promacine. Doses of 1 mg/kg were administered without observing any visible changes in their behavior.
Attempts were made to capture 21 of the 32 animals seen with hoops. Thirteen were successfully captured. Of these 13, six were captured on land and the rest in the water. In all cases a rope lasso was utilized while working in the water in order to keep the animal under control. The rope was more effective than a net in the water, but nets were more effective on land.
Animals without hoops were always injected in the hip region with 50 ram needles while resting. Injections were made at right angles to ensure that the drug was released intramuscularly.
Discussion
It is difficult to establish the most effective dose for entangled animals despite the full range of doses tested. This difficulty is due to the contradictory effects produced. One dose, for example, proved fatal for one animal but had no effect on four other animals. This can be caused by one or a combination of the following factors:
1. There could have been a significant error in the estimation of the weight. Very little data is available to make such estimates. This factor is mentioned by Trillmich (1979).
2. The agitation caused by capture could be a determining factor. Trillmich (1979) cites two similar cases of adult female South American sea lions (O. flavescens) that were injected with doses of Ketamine- after parturition but showed no effect. The physiological stress of giving birth may have made these animals resistant to the drug.
It was observed that the animals with hoops exhibited different degrees of excitation which lengthened the times of induction and diminished the effects of the drugs so that much higher dosages were needed. In animals without hoops shorter and more homogeneous induction times were noted after minimizing all stimuli that would cause tension. In the present study, animals without hoops showed better reaction to the drug using smaller than average doses than the animals with hoops.
The site of impact of the dart may be art important factor affecting the effect of the immobilizing drug. Injections in the subcutaneous fat tissue resulted in slow absorption of the drugs. Jewell and Smith (1965) indicated that injections in grey seals often failed when the needle was not able to pass the subcutaneous tissue layer. Cline et al.(1965) had the same problem working with different species of Antarctic seals. They found that when needles were injected in the subcutaneous fat layer there was a delayed reaction and a prolonged period of induction. Animals injected in areas of heavy fat tissue were therefore giver, an additional dose.
It was necessary for an animal to reach a Class 3 immobilization before workers could remove the hoops. A Class I immobilization was sufficient while working in water.
The effects of Xilazine on animals without hoops were similar to the effects observed by Cardenas and Cattan (1984). To test the effects of Xilazine on adult males of go flavescens they utilized 0.8 mg/kg to produce partial immobilization in one animal, 1.2 to 2 mg/kg to produce less effect in four animals, while 0.67 mg/kg in a sixth animal was an insufficient dose.
In this study, a combination of Ketamine and Xilazine was utilized in only three animals. Two animals without hoops that received low doses of 0.4 mg/kg to 0.8 mg/kq arrived at a Class I immobilization level. One animal received a dose of 2.1 mg/kg of Ketamine and 12.6 mg/kg of Xilazine and died in 127 minutes.
Due to the pronounced depressor effect of Ketamine on the respiratory system of these animals, and because of the considerable margin of error in the body weights, low doses were preferred in comparison to those used or, other pinnipeds by Trillmich (1979, 1983), Parry (1981), and Baker and Gatesmar, (1985). The data obtained on Ketamine provide valuable information regarding the future use of this drug as a pinniped tranquilizer, both alone and in combination with other drums.
The results obtained in this study from the use of Hyaluronidase do not coincide with the results of Haigh (1979), or Thomas (1970), where they noted a shortening of the induction period. In the present work no difference was observed in the effect of Xilazine when used in combination with Hyaluronidase.
Based on the data obtained in this study, it is recommended that future work with entangled pinnipeds requiring the use of tranquilizers avoid all external stimulus to the animal being injected since the stimulus will influence the effect of the tranquilizers.
Editor's Note: The table has been omitted as it was not readable in the original provided pdf.
References
1. Baker, J.Y. and T. Gatesman. 1985. Use of Carfentianic and Ketamine-xilazine mixture to immobilize wild grey seals (Harichoerus grypus). Vet. Rec. 116, 208-210.
2. Bonner, W.T. and T.S. Mccann. 1982. Neck collars on fur seals Arctocephalus gazella) at South Georgia. British Antarctic Survey Bulletin. No. 57 pp. 73-77.
3. Cardenas J.Y. and P. Cattan. 1984. Administracion de clorhidrato de Xilacina en otaridos en condiciones naturales mediante el empleo de cerbatana. Primera reunion de trabajo de expertos en mamiferos acuaticos de America del Sur. Resumenes 25-29 De Junio 1984. Buenos Aires, Argentina. pp. 14.
4. Cline, R.D., D.B. Siniff and A.W. Erickson. 1969. Immobilizing and collecting blood from Antarctic seals. J. Wild. Manag. Vol. 33 no.1 Jan.
5. Haign, J.C. 1979. Hyaluronidase as an adjunct in an immobilizing mixture for moose. J.A.V.M.A. Vol. 175 No. 9 pp.916-917.
6. Jewell, P. and E.A. Smith. 1965. Immobilization of Grey Seals. J. Wild. Manag. Vol. 29 No.2.
7. Parry K., S. Anderson, and M.A. Fedak. 1981. Chemical immobilization of gray seals. J. Wild. Manag. 45 (4) pp. 986-990.
8. Payne M.R. 1919. Fur seals Arctocephlus tropicalia and A. gazella crossing the Antarctic convergence at South Georgia. Mammlia, 43, pp. 93-98.
9. Thomas, J.A. 1970. Immobilization of white-tailed deer with sucCinylcholine Chloride and Hyauronidase. J. Wild. Manag. Vol. 34 No.1 pp. 207-209.
10. Trillmich, F. 1979. Immobilization of tree-ranging Galapagos sea lions. (Zalophus californianus wollebaeki) Vet. Record Nov. 17 pp. 465-466.
11. Trillmich, F. 1983. Ketamine xylazine combination for the immobilization of Galapagos sea lions and fur seals. Vet. Record 112(12)pp.279-280.