Co-operative Hunting in

Sandtiger Sharks

Despite the popular conception of sharks as 'lone killers', many species feed in groups and a few even appear to co-operate in prey-capture. Sandtigers have occasionally been reported to feed co-operatively. In 1915, pioneer shark-watcher Russell J. Coles reported on the astonishingly co-ordinated manner in which a group of Sandtigers off Cape Lookout, North Carolina, concentrated and captured a school of Bluefish (Pomatomus saltatrix). According to Coles, a school of a hundred or more Sandtigers systematically surrounded the school of Bluefish and herded them into shallow water, where at the same instant the pack of sharks dashed in and attacked their nearly-stranded prey.

Similar co-operative herding behavior and use of bottom topography to strand schooling fishes has often been observed in Bottlenose Dolphins (Tursiops truncatus) feeding on mullet (family Mugilidae) at several coastal wetland locations off the southeastern United States. All schooling or herding animals crowd together instinctively when faced with a hunting predator. But, unless contained very skillfully, such prey animals tend to be quite adept at finding and flowing through any momentary opening and thereby making good their escape. Yet fishes however exquisitely agile in their liquid element are all-but helpless when confined in very shallow water. Thus, if Cole's report is reliable, it suggests that the Sandtigers employed basic understanding of the escape responses and limitations of their prey.

Such reports of co-operative feeding in Sandtigers are not uncommon. At Seal Rocks, New South Wales (about 185 miles or 300 kilometres north of Sydney, Australia), a diver reported a pack of Sandtigers known locally as Grey Nurse Sharks herding a small shoal of juvenile Yellowtail Kingfish (Seriola lalandi). The sharks accomplished this by whipping their tails to generate sharp underwater pressure waves, which sound very like the reports of a shotgun. This caudal fin whip-cracking immediately calls to mind the similar prey-stunning technique employed by thresher sharks (family Alopiidae) in open water when feeding upon small shoaling fishes.

What is perhaps most intriguing, however, is that adult female Sandtigers in underwater caves at Protea Banks (off the Natal Coast of South Africa, near Durban), are known to perform a similar tail whip-cracking behavior toward divers, possibly indicating defensive threat. Similar tail whip-cracking behavior has been reported between two large White Sharks (Carcharodon carcharias) off the Cape Coast of South Africa. Thus, shark behaviors used in herding and disabling prey may also be employed ritualistically in agonistic encounters, whether directed toward members of their own species or monkeys encased in neoprene.

 

ReefQuest Centre for Shark Research
Text and illustrations R. Aidan Martin
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