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APPENDIX A

TAGS ON WHALES, DOLPHINS, AND PORPOISES

Field studies of cetaceans are very difficult. First, it is extremely hard to be positive that an individual or a group of animals is the same from one encounter to the next. This means that it is nearly impossible to determine, for example, whether herds of animals are resident in an area or only seasonal visitors. Without information of this kind, determinations vital to population management, such as sizes of populations and natural ranges, are impossible to make.

Secondly, as we frequently point out in this guide, individual cetaceans are usually visible to a surface observer only during the brief moments when they break the air-water interface to breathe. The majority of their vital activities (e.g., feeding, reproduction, communication, establishing and maintaining position within the herd, and defending against natural enemies) take place primarily below the surface, well out of view to a surface observer.

In recent years, in an attempt to overcome some of these problems, scientists have been placing markers on various species of cetaceans and monitoring their movements. The following brief summary of major methods of tagging cetaceans is provided to acquaint the reader with markers he may expect to see in the western North Atlantic.

Static Tags

Since their development in the mid-1920's, numerous Discovery marks (small stainless steel projectiles with identifying information stamped on them) have been shot into commercially valuable species by means of a shotgun. The recovery of these marks from whales subsequently killed in the whaling industry has provided valuable information on the movement patterns and on basic aspects of the growth and development of harvested species of whales. Discovery marks are limited, however, because they are not visible in a living animal. Reduction in whaling activities will bring about a significant reduction in their use.

More recent tagging developments relate to marks which will be visible on a free-swimming animal. Large whales, for instance, may be tagged with color-coded streamers, such as that shown in Appendix Figure A2.

The tags, which are modified versions of the spaghetti tags first constructed for use on fishes, consist of a small stainless steel head for attachment to the blubber and a colorful streamer (sometimes stamped with information on agencies to which tags should be returned) which is visible above the surface of the animal. These tags may be applied by using either a pole applicator or a crossbow and crossbow bolts. Both applicators are equipped with a stop to limit the depth of penetration into the animal's blubber. Extensive experimentation indicates that the tags do not harm the animals and that their application is not traumatic. With the continued reduction in whaling activity, it is hoped that the use of such markers in the study of movements of big whales will be increased.

Because they often ride the bow wave of a moving vessel, thereby making themselves accessible for tagging and capture, small porpoises and dolphins have been tagged with a greater variety of marks than large whales. In recent years, at least three kinds of static tags, including spaghetti streamers, have been placed on small and medium-sized cetaceans.

Spaghetti tags, placed in the animal's blubber near the base of the dorsal fin as it rides the bow wave, stream to conform to the contour of the animal's body as it swims (App. Fig. A3). It is not possible to identify the numbers on the spaghetti tag of a moving animal, although color codes may be used to indicate different species, populations, or tagging areas.

b.u.t.ton tags and freeze brands are placed on captured animals prior to their release. The b.u.t.ton tags (App. Figs. A4, A5) are placed in the dorsal fin and should be visible as the animal surfaces to breathe or as it rides the bow wave. At close range, the number, letter, or design may also be visible. Freeze brands (App. Fig. A6) are placed on the back or dorsal fin with a supercooled branding iron, apparently without pain or discomfort to the animal, and provide a permanent mark which leaves the tagged animal free of enc.u.mbrances. The use of freeze brands shows promise and should come into more extensive use.

Other static tagging techniques currently under investigation include the use of laser beams to apply small brands and the use of gas branding devices. Neither technique, however, has yet reached the field biologist.

The success of any tagging program using static tags depends on the resighting of tagged animals and the recovery of tags. For that reason, we appeal to readers to be on the lookout for tagged animals and to report sightings to one of the authors.

[Ill.u.s.tration: Appendix Figure A1.--Some of the basic kinds of tags used to mark porpoises, dolphins, and small whales. A, B, and C are nylon b.u.t.ton tags, which are placed in the dorsal fin of animals and may be clearly visible as the animal surfaces to breathe. D is a vinyl spaghetti tag. (_Photo by R. Krenic, courtesy of Naval Undersea Center._)]

[Ill.u.s.tration: Appendix Figure A2.--A spaghetti tag in the back of a blue whale off San Clemente Island, Calif. (_Photo by S. Leatherwood._)]

[Ill.u.s.tration: Appendix Figure A3.--A spaghetti tag in the flank of a bottlenosed dolphin off Loreto, Baja California, Mexico. This particular tag was placed unusually low. The streamer and spaghetti tags are usually placed high on the back, just in front of the dorsal fin, and are clearly visible as the animal surfaces to breathe. (_Photo by W. E.

Evans._)]

[Ill.u.s.tration: Appendix Figure A4.--A b.u.t.ton tag placed on the dorsal fin of a newly captured saddleback dolphin off Catalina Island, Calif.

(_Photo by W. E. Evans._)]

[Ill.u.s.tration: Appendix Figure A5.--This is the way the b.u.t.ton tag appears on an animal swimming free in the open sea off Palos Verdes, Calif. (_Photo by B. n.o.ble, courtesy of Marineland of the Pacific._)]

[Ill.u.s.tration: Appendix Figure A6.--Freeze-branding is an apparently painless method of applying a permanent identifying mark to the body of a porpoise or whale. (_Photo of a bottlenosed dolphin off Sarasota, Fla., by A. B. Irvine._)]

Radio Transmitter Tags

In recent years, radio transmitter tags have been developed for use on marine mammals. As they continue to become more reliable, these tags are expected to come into more and more widespread use.

Early radio tags (Fig. A7) were simple locator beacons which permitted the animal to be tracked by sending a signal to a tracking vessel or aircraft every time the animal surfaced and the antenna tip was exposed.

Even these basic packages provide important information on movement, activity patterns, and respiration rates.

Subsequent developments have involved the addition of sensors to monitor the maximum depth of each dive and environmental parameters such as the water temperature at that depth (Fig. A8).