Figure 4. — Mother and young swimming with harness and radio in place. 



dark, and the animal was lost during 

 the night. However, shortly after dawn 

 the released harness was found floating 

 within 60 m of the vessel. Details 

 of these releases and trackings are 

 presented in Table 1. 



DISCUSSION 



The capture methods described here 

 for suckling gray whales are remark- 

 ably effective and simple. Except when 

 the mother is under the pulpit or at 

 the edge of shallow water, the methods 

 seem relatively safe. Given enough 

 shipboard power the noosing methods 

 would work with larger animals, 

 though the sheer bulk of an adult 

 would make any movement by the 

 whale, purposive or not. dangerous. 

 This would certainly be a prime con- 

 sideration in any attempt to affi.x a 

 harness on an adult. 



The harness described here would, 

 with minor modifications, serve nicely 

 for short-term tracking and instru- 

 mentation of small gray whales. Be- 

 cause a whale attains 66-72 percent of 

 its adult size in the first year (Rice 

 and Wolman. 1971). growth during 

 the first months is e-xtremely rapid. 

 Harnesses for periods of more than a 

 week must therefore include a device 

 that allows for growth but also keeps 

 a constant tension and locks if the 



Table 1. — Harnessing and tracking of gray whale calves. 



animal rubs the harness against under- 

 water obstructions. 



Another concern on any long-term 

 track is abrasion of the harness. The 

 purposive rubbing of whale No. 1 

 against the capture ship and its mother 

 caused damage to the radio antenna 

 and serious abrasion to the lower har- 

 ness legs. On whale No. 2 the abdomi- 

 nal legs of the harness were abraded 

 through the girdle fabric and into the 

 flat nylon strap in several places, even 

 though the animal wore the harness 

 for only ?• hours. 16 minutes. Behavi- 

 oral observations suggest that much 

 harness wear results when the baby 

 rubs against the barnacle-covered 

 back of the mother and slides to one 

 side as she surfaces. None of these 

 problems was more than very minor 

 in these tests. But clearly long-term 

 tracking with increased exposure to 

 obstacles along the migratory path 



will exacerbate these problems greatly. 

 More durable materials, such as metal 

 or the strongest fabric, and more re- 

 silient radio antennae will be needed 

 for successful long-term tracking. 



The release mechanism dependent 

 upon magnesium bolt corrosion worked 

 adequately, but variations in water 

 temperature and salinity could un- 

 predictably alter release time. Long 

 release times (more than a week) may 

 require a new system, such as the use 

 of electroexplosive or electronic re- 

 lease mechanisms that might allow an 

 operator to release the harness upon 

 command. 



Harnessing is probably the least 

 injurious means of attaching instru- 

 ments to cetaceans, and harness place- 

 ment around the pectoral flipper area 

 is probably optimal. Pectoral place- 

 ment insures maximum exposure of 

 the antenna, minimal body movement 



63 



