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Fishery Bulletin 98(3) 



Figure 2 



A 3.5-m PCL tiger shark feeding on a Bryde's whale carcass at the water line. The 

 shark's eye is covered by the nictitating membrane. 



Moss, 1972; Strong, 1991). One approach behavior exhib- 

 ited by the white shark and captured on fihii conformed 

 with that described by Tricas (1985) as an underwater 

 approach, in which the shark approached the carcass just 

 below the surface until approximately 1 m away and then 

 attacked by deflecting the head upward, emerging out of 

 the water to bite. When feeding above the water line, both 

 species tended to bite twice in quick succession, apparently 

 gaining better purchase with the second bite. This proce- 

 dure was followed by slow and deliberate shaking, twist- 

 ing, and turning to cut away the mouthful. The tiger sharks 

 demonstrated more thrashing than the white shark, some- 

 times rolling onto their backs while biting. The white shark 

 behavior described by Pratt et al. (1982), in which the 

 shark bit a whale carcass ventral-surface-up before rolling 

 upright to cut a mouthful, was not seen. 



When tiger sharks fed below the surface, the carcass was 

 penetrated vertically and a swaying motion of the body, rather 

 than twisting, followed the bite. As many as five individual 

 tiger sharks fed on the carcass at one time, some hanging 

 below the carcass and some biting at the waterline. 



The tiger sharks tended to remain at or near the carcass 

 at all times, whereas the wounded white shark approached 

 the carcass to feed and then moved off again, sometimes out 

 of sight of the observers. A white shark of 3.5-4 m, believed 

 to have been an individual not previously observed, made 

 a brief appearance near the carcass during this period. The 

 tiger sharks were generally more active than the wounded 

 white shark, although both species were unhurried and 

 deliberate. The white shark increased swimming speed 

 only when investigating the camera. . 



The red inflatable boat which had been present earlier, 

 returned, and the wounded white shark again showed par- 

 ticular interest in it. On one occasion the shark held the 

 rear of the starboard pontoon in its mouth and kept the 

 boat stationary despite the crew of the boat engaging gear 

 and running the 40-hp motor at speed. After 10 sec the 

 shark released the pontoon, the only damage to which was 

 a single, small puncture, perhaps the result of exploratory 

 mouthing behavior. 



Discussion 



White sharks feeding on whale carcasses appear to feed until 

 satiated (McCosker, 1985). The observed regurgitation of food 

 suggests that feeding may continue even after satiation. 



Observations suggest agonistic encounters amongst 

 white sharks when feeding on a whale carcass. Observers 

 saw at least four and possibly up to nine different white 

 sharks in the vicinity of a fin whale carcass, Balaenoptera 

 physalus, over a 30-h period but never more than two 

 together (Pratt et al., 1982). When two did co-occur their 

 behavior appeared agonistic, and some of the sharks had 

 tooth cuts and slashes (some previous wounds, some freshly 

 inflicted). Similarly, Long and Jones (1996) reported that 

 about five cjifferent white sharks fed on the carcass of a 

 blue whale, Balaenoptera musciilus, but only one fed at 

 a time. McCosker (1985) observed an agonistic encounter 

 between two white sharks feeding on horsemeat bait; the 

 smaller shark was forced to depart after receiving a minor 

 bite. Strong et al. (unpubl. data in Strong 11996]), also 



