NOTE Dudley et al ; Scavenging off a whale carcass by Carcharodon carchonas and Galeocerdo cuvier 



647 



Figure 1 



A 4-m PCL white shark feeding on the carcass of a Bryde's whale, and a 3.5-ni tiger 

 shark swimming below it. The head of the white shark, out of picture, is above water 

 The boat hull is at upper left, and strands of whale tissue are hanging beneath it. 

 (Frame from Hi8 videotape). 



initially, was observed surfacing 100 m from the carcass 

 and regurgitating its stomach contents. It then circled 

 the floating matter. While being approached by the boat, 

 it began to feed on the regurgitated material. This was 

 the only time that regurgitation was observed but, on 

 other occasions, clouds of what appeared to be regurgitated 

 matter were seen in the water near the carcass, indicating 

 that regurgitation may have occurred more frequently. 



Subsurface filming of the white shark was conducted 

 over the gunwale. On five or six occasions the shark 

 approached the camera (which was enclosed in a yellow 

 housing) such that the cameraman was forced to lift the 

 camera out of the water just prior to the shark's snout 

 making contact. The shark would then mouth (lightly and 

 briefly grasp) the boat or motors before moving off. On one 

 occasion it damaged its head on the motor and the result- 

 ing laceration, immediately anterior to the right eye, was 

 used subsequently as an identification mark. 



A small (3-3.5 m), red, semirigid, inflatable boat arrived 

 and the white shark immediately showed interest in it, 

 approaching it from the rear several times and mouthing 

 the motor. 



After 40 min, the observers (coauthors) returned to close 

 proximity of the carcass, where there now appeared to 

 be between 7 and 10 tiger sharks, all 3.5 m. Feeding on 

 the carcass continued, but the animals showed more inter- 

 est in the boat than previously. Typically, a shark would 

 leave the boat, feed on the whale and then return slowly 



to the vicinity of the boat. The motors were bumped three 

 times and a propeller was mouthed once. As with the white 

 shark, the tiger sharks approached the camera directly, 

 and on several occasions the cameraman depended upon 

 warnings from his co-observers to ensure timely evasion. 

 Only one interaction between individual tiger sharks was 

 observed. Two animals, swimming one above the other, con- 

 verged slowly to within 1 m, at which point they diverged 

 rapidly. Immediately prior to this event, one of the animals 

 had been investigating the camera and it is possible that 

 it had been unaware of the other shark's presence. 



Soon after returning to the carcass, the observers noted 

 the arrival of the white shark with the wounded snout. 

 There appeared to be a slight increase in the swimming 

 speed of the tiger sharks but no other reaction was 

 observed. The white shark fed on three occasions and on 

 each occasion one or more tiger sharks fed at the same 

 time. On one occasion two tiger sharks swam within 3 

 m of the feeding white shark — one of these was captured 

 on videotape, together with the white shark (Fig. 1). The 

 white shark removed a piece from the carcass, then aban- 

 doned the piece and returned to the carcass. A tiger shark 

 then fed on the piece but moved off when the white shark 

 came back to it. 



Both species fed on the carcass at the water line, but the 

 tiger sharks fed below the water line as well. Tiger sharks 

 were observed to thrust their heads out of the water to feed 

 (Fig. 2) as has been observed previously (Gilbert, 1963; 



