paints applied underwater and kept immersed for 

 13 days and 7 h at 3.5°C showed only slight 

 differences from short-term tests. There was little 

 difference in the painted surfaces down to a 

 temperature of 4.0°C. Below this, less paint ad- 

 hered, and the color of the painted surface was 

 duller. The paint maintained a coherent stream to 

 greater depths in warmer water, perhaps because 

 of associated higher air temperature and there- 

 fore greater pressure in the can. With the appar- 

 atus above water, penetration and marking (at 

 15°C) occurred to a depth of about 40 cm, and with 

 increasing depth progressively less paint adhered. 

 Comparisons of application of these paints in both 

 seawater and fresh water showed little difference, 

 at least on a short-term basis. 



Since only a portion of the paint actually ad- 

 hered underwater, the residue of these paints 

 floated as an inert scum in temperatures of 5°C or 

 warmer, generally not sticking to anything. This 

 was in sharp contrast to many other paints that 

 often floated as soft globules on the water, and for 

 hours thereafter would coat any objects they 

 contacted. 



A Lagenorhynchus acutus was successfully 

 marked in the open ocean on 8 May 1975, 8 to 10 km 

 northeast of Race Point, Cape Cod, Mass. Though 

 L. acutuf^ usually is shy of ships and diflicult to 

 approach (Schevill 1956), we found about 30 of 

 these animals and were able to get close to a 

 subgroup of six porpoises. They would not surface 

 within reach of our vessel (13-m RV Asterias), so 

 the paint was applied through 15 to 20 cm of water. 

 The paint mark was a 10-cm circular red spot at 

 the after part of the buff-colored stripe on the right 

 side. We were able to follow this porpoise for only 

 30 min, but during this time, the mark provided a 

 highly visible tag which permitted rapid iden- 

 tification of the marked individual as well as the 

 subgroup of animals. This subgroup appeared to 

 stay together even when mingling with others of 

 the larger porpoise aggregation. Again, the paint 

 mark appeared to be ignored by all of the animals. 

 The next day, two schools of L. actus (probably 

 including the same animals) were studied, but no 

 mark could be found. 



Discussion 



Results 



On 16 December 1974, we tested both paints on a 

 captive Tursiops (one of two in a tank) at the 

 Naval Undersea Center, San Diego, Calif. The 

 porpoise swam slowly past with all but its dorsal 

 fin underwater. The holder for the paint can was 

 hand-held about 20 cm above the water, and the 

 paint stream was directed downward at the an- 

 imal, about 20° from the vertical. The stream 

 penetrated the water by as much as 15-20 cm, 

 marking a streak 6-8 cm wide (at each pass) on the 

 animal's back, as well as on the right side of the 

 dorsal fin. 



The paint contrasted sharply with the dark gray 

 color of the animal and provided a conspicuous 

 mark that was brightly visible 8 h after applica- 

 tion, although patches of it had disappeared. 

 Twenty-four hours after painting, only a small 

 strip of paint (at the leading edge of the dorsal fin) 

 remained, and much of this residue was still there 

 56 h after application, though quite dulled. 



Of the two Tursiops in the tank only one was 

 painted, yet no obvious behavioral changes could 

 be noted; they both seemed to ignore the whole 

 process and behaved as before. There was no 

 . obvious reaction to either the painted animals or to 

 the excess paint floating on the water. 



We suppose that the paint on the leading edge of 

 the dorsal fin of the captive porpoise persisted 

 longer than elsewhere because of the roughness 

 and scarring of the skin there. The disappearance 

 of the paint from the smooth surfaces on both the 

 captive and wild animals was apparently because 

 of the normally rapid sloughing of surface layers 

 of skin. Palmer and Weddell (1964: 555) noted that 

 cells in Tursiops skin undergo mitosis 250 to 290 

 times as rapidly as human skin, and Harrison and 

 Thurley (1972) also reported that cells in the 

 surface layer are desquamated in large numbers. 

 Presumably, the paint came loose because the 

 surface cells sloughed off. The relative stiffness 

 and greater mass of the cells coated with paint 

 would have accelerated their removal, but after 

 the paint had worn off, no difference in the skin 

 surface could be noted. We could find no indica- 

 tions of any adverse effects. Since the paint lasted 

 so much longer on the rough part of the fin, we 

 anticipate that similar nonsloughing surfaces on 

 the other cetacean species also would hold a paint 

 mark well (e.g., the highly barnacled portions of a 

 gray whale, or perhaps right whale bonnets). In 

 addition, we anticipate that such paints could 

 usefully mark other aquatic animals (turtles, seals, 

 manatees, etc.). 



Little is known about color vision in porpoises. 



688 



