Shark Ecology 101
Do sharks have any enemies other than humans?
Sharks’ greatest enemies, after humans, are other sharks. Several of the
larger species—Tiger, Bull, White, and sleeper sharks—are known sharki-
vores. Cannibalism within a species is also common, as shown by Lemon
Sharks in the Bahamas. One species of shark may even feed preferentially on
another, as is true with the Broadnose Sevengill Shark (Notorynchus cepedia-
nus), whose main prey off Tasmania, Australia, is the Gummy Shark. Some
seemingly lethargic sharks are also successful predators on sharks; Tasselled
Wobbegongs (Eucrossorhinus dasypogon), for instance, are able to ambush
Brown-banded Bamboo Sharks on the Great Barrier Reef of Australia.
The shark-eat-shark nature of the ocean is probably the reason that
females of many species go to particular nearshore “pupping grounds” to
give birth to their young. These shallow inshore areas are infrequently vis-
ited by the males of the pupping species or by most large, predatory oce-
anic species.
Rays are another favorite prey of several shark species. Some hammer-
heads appear to be stingray specialists. Individual Great Hammerheads
have been found with as many as 96 stingray barbs embedded in their
mouth, throat, and tongue. Divers in the Bahamas watched a 3-m (10-ft)
Great Hammerhead knock a Southern Stingray down with its flattened
head, pin the ray to the bottom, then rotate on the ray and take bites out
of the ray’s wing.
Although we don’t have such spectacular firsthand reports of sharks
feeding on other rays, we do have circumstantial evidence. Manta rays ob-
served at Tofo, Mozambique, have huge scars on their backs that indicate
they were chomped on by large sharks and survived. Injured mantas, with
fresh wounds, hover at “cleaning stations” on the Tofo reef, where various
cleaner fish nibble at the wound to remove dead tissue and presumably
A Broadnose Sevengill Shark cruises
a kelp bed off South Africa. Seven-
gills occur in temperate Pacific and
Atlantic shallow-water locales and
feed on other sharks, rays, and chi-
maeras. Photo by Austin Gallagher, http://
austingallagher.com; used with permission