Equipment and Techniques for Handling 

 Northern Fur Seals 



ROGER L. GENTRY and JOHN R. HOLT 1 

 ABSTRACT 



This paper describes techniques for capturing, immobilizing, and marking northern fur seals, Ca/- 

 lorhinus ursinus, of all ages and both sexes. It is intended as an explicit field manual for handling this species, 

 and as a source of ideas for handling other eared seals, wild or captive. Furthermore, it advocates capturing 

 and manipulating wild seals as an approach to investigating behavior. The paper deals only with short term 

 physical restraint; immobilization with drugs is not considered. Emphasis is placed on the importance of ani- 

 mal behavior in determining the design of capture equipment and techniques. Because of this dependence, cap- 

 ture techniques must change seasonally as behavior changes, and different techniques may be needed for 

 different species. A wide range of techniques is considered, from the capture of single pups to the mass cap- 

 tures of adult females. 



INTRODUCTION 



Field studies on the Otariidae (fur seals and sea lions) have not 

 matured beyond the level of passively observing wild populations 

 (Gentry 1975). The limitations of this approach are obvious; it will 

 never reveal cause and effect relationships, and it will not serve for 

 detailed hypothesis testing. Without adopting more complex field 

 methodology otariid studies are not likely to match the level of 

 sophistication reached in primate field studies (compare Ronald and 

 Mansfield 1975 against Chevalier-Skolnikoff and Poirier 1977). 



The use of manipulative field experiments by primatologists marks 

 the difference between the two disciplines. Otariid researchers too 

 can perform experiments on wild animals given a set of handling 

 techniques, some simple tools, and the conviction that small distur- 

 bances are justifiable. Obviously, not every animal of every species 

 can be manipulated. But at least some animals of most species can be. 

 The subject of this manual, the northern fur seal, is one of the more 

 tractable otariids. 



The equipment and techniques described here were developed dur- 

 ing the past 8 yr. Some of the methods have been used successfully on 

 the Afro- Australian fur seal, Arctocephalus pusillus pusillus, and the 

 Antarctic fur seal. A. gazella. With modifications, the techniques and 

 equipment could be used on other otariids as well. Some of the equip- 

 ment we describe have had a long history of successful use in the Pri- 

 bilof Islands, and some we have invented. We developed the 

 techniques for using this equipment around two criteria specific to 

 our behavioral studies: 1) the methods of capture and handling a 

 given animal should cause the least possible disturbance to other seals 

 and 2) the prolonged debilitating effects of drugs are to be avoided. 

 Because other workers will have different criteria, this manual 

 presents convenient starting points for the development of techniques 

 that meet other criteria. That is, our techniques are not offered as 

 "correct," only successful. 



We intend this as a field manual for those who have had no pre- 

 vious experience with otariids and who must capture and handle ani- 

 mals without the aid of experienced help. The immobilization 

 techniques are applicable to any captive otariids. All the equipment 

 we describe can be built and maintained in the field with minimal 



'Northwest and Alaska Fisheries Center, National Marine Mammal Laboratory. 

 National Marine Fisheries Service, NOAA, 7600 Sand Point Way NE. , Seattle. WA 

 98115. 



tools. Techniques for keeping seals in captivity have recently been 

 reviewed (Spotte 1980). 



IMPORTANCE OF BEHAVIOR 



The key to successfully handling wild otariids is knowing their 

 behavior thoroughly. Knowing their strengths and weaknesses often 

 suggests a design for some special equipment. But more importantly, 

 knowledge of how animals act reduces one's fear of the animals and 

 fosters the calm judgement under stress that capture situations 

 demand. Inevitably, judgement is most important at the moment of 

 greatest physical exertion during a capture. The use of too much 

 force can injure or kill the seal, but insufficient force can allow the 

 seal to escape and endanger humans. A knowledge of behavior gives 

 one the judgement to maintain a balance between force and finesse, 

 and the flexibility to improvise during captures. No two animals are 

 exacdy alike, and no one set of procedures works equally well in all 

 captures. Furthermore, the behavior of animals changes throughout 

 the year so extensively that seasonal changes in capture techniques 

 are required for a given age and sex (Table 1). 



Most of the techniques in this manual take advantage of some spe- 

 cial behavioral trait of northern fur seals. If a different species does 

 not share that trait the technique will not work as described. How- 

 ever, the approach to developing techniques should be the same for 

 all species. Basically, one learns the behavioral traits well, and then 

 uses those traits for their direct effect, or selectively avoids them. For 

 example, northern fur seal males aggressively charge a human in 

 response to a direct, fixed stare. Charging is desirable when trying to 

 lasso the seal properly, and it can be induced by staring. In contrast, 

 charging is not desirable when capturing adult females from within 

 the male's territory, and it may be prevented by averting the face from 

 the male. Where possible we advocate capture by trickery, rather than 

 by force. 



There are four generalizations about otariid behavior that influ- 

 ence handling techniques and equipment. First, the animals will not 

 attack a human with the same determination as they would another 

 seal. It is usually not appropriate to bolt and run from an attack, rather 

 to cautiously withdraw. Overreaction to attack can jeopardize your 

 coworkers. Second, otariids are physically strongest in the vertical 

 direction due to the development of their pectoral muscles. They are 

 powerless on their backs or suspended in the air. Unlike phocids they 

 are relatively weak in side-to-side motions, and the design of restraint 



