The classic reef shark shape at 1.8 to 2 m (6 to 6.5 ft): gray above, white below, blunt-snouted, with a broad black band along the rear edge of the tail that identifies it at a glance. Populations in this ocean often carry a narrow white tip on the first dorsal fin, which Pacific animals lack.
It is one of very few sharks that will tell you before it bites. Pressed too closely or cornered, it drops into an unmistakable posture: pectoral fins angled down, back arched, snout lifted, swimming in an exaggerated rolling figure-of-eight. The display was described in the early 1970s and it is a warning with a meaning as fixed as a rattlesnake's. Back off and it stops. Keep closing and the animal will make a fast slashing pass. Almost every bite on a diver has followed an ignored display.
Day to day it is a social animal with a home range rather than a territory, hunting reef fish and cephalopods, patrolling a stretch of drop-off it may hold for years. Groups of five to twenty are normal along a wall, and they move up the reef at dusk.
The display is not aggression in the human sense but bookkeeping: a fight costs the shark more than it can gain from a diver, so it advertises instead. Understanding that turns the most commonly encountered reef shark here from a hazard into a readable animal. The species is Endangered globally.
The species. Carcharhinus amblyrhynchos (Bleeker 1856) - amblýs (blunt) + rhýnchos (snout). ETYFish
- broad black band along the rear edge of the tail
- plain first dorsal fin, sometimes with a narrow white tip
- no ridge of skin between the dorsal fins
- arched back and lowered pectoral fins when it wants space
Why it's threatened
Threat classification from the IUCN Red List.
