EVANS ET AL. ; TAGGING SMALL CETACEANS 



To meet this need, a new lightweight radio tag 

 (170 g) with a 9-12 month transmitter life was 

 developed. This tag combines the advantages of 

 a radio beacon and a button tag in that it contin- 

 ues to serve as a color coded marked even after 

 it no longer transmits (Figure 3), Further- 

 more, the new radio tag is available commer- 

 cially at less than 10 ^r of the cost of the 900/gm 

 transmitters. 



Figure 2. — Three Lagenorhynchus obliqiddens with the 

 plastic button tag, just prior to release. 



Island, Baja California. Two of the L. obliqui- 

 dens tagged in 1969 were resighted almost 1 year 

 later, and a D. delphis tagged in 1968 was re- 

 sighted 21 months later. 



Twenty-four T. truncatus were tagged with 

 the button tags near Sarasota, Fla., from August 

 1970 through September 1971. Animals bearing 

 tags have been resighted several times. 



The third and most successful short-term tag 

 is the radio transmitter tag with which at least 

 four species of small cetaceans have been success- 

 fully marked to date (Evans, in press, Martin, 

 Evans, and Bowers, 1971) . The original package 

 used in these studies was a 27 mHz (11m) trans- 

 mitter and antenna housed in a waterproof 

 envelope which is attached to the dorsal fin of a 

 dolphin or a small whale by means of a spring- 

 loaded corrosible link. The link dissolves and 

 releases in 30 days, allowing the package to slip 

 off the animal. 



These early radio beacons, designed for short- 

 term transmission (30-60 days), weighed up to 

 900 g, and though they proved especially useful 

 in studying the detailed movements of D. delphis 

 in the waters off San Diego, Calif., their size, 

 cost, and relatively short transmission time made 

 them unacceptable for long-term monitoring of 

 herd movements. 



Figure 3. — The lightweight (170 g) radio tag. 



63 



