Tiger Shark

The tiger shark is the ocean’s least fussy eater. It patrols warm coastal seas around the world eating whatever it comes across — living, dead, or, occasionally, made of rubber and metal — and in doing so it plays a surprisingly important role in keeping shallow-sea ecosystems in balance.

Overview

Tiger sharks are found throughout the tropics and warm-temperate zones, from murky river mouths and reef flats to the deep open ocean. They are highly nomadic, with tagged individuals crossing entire ocean basins, but they also return seasonally to specific hunting grounds — the waters off Hawaii when albatross chicks fledge, for example, or seagrass banks off Western Australia.

Physical characteristics

An adult tiger shark is a blunt-nosed, heavy-bodied shark, typically 3.5–4.5 m long, grey to bronze on top with the faint remnants of the juvenile “tiger” bars along the sides. The head is broad and wedge-shaped, and the upper tail lobe is long, giving a slow, sweeping swimming style that can shift instantly into a fast lunge.

Its teeth are unlike a great white’s. Each is short, curved, and edged with coarse serrations and a deep notch — a design for sawing rather than slicing, capable of cutting straight through the shell of a large sea turtle.

Diet

The tiger shark’s recorded diet is the broadest of any shark: bony fish, rays, other sharks (including smaller tiger sharks), sea turtles, sea snakes, seabirds, seals, dolphins, crustaceans, squid, jellyfish, and carrion of all kinds. Alongside this it swallows indigestible objects — the reason it is called “the garbage can of the sea” — some of it apparent curiosity, some the result of investigating floating debris that resembles prey.

This willingness to eat anything makes the tiger shark an effective scavenger and a generalist predator that can thrive where pickier sharks cannot.

Its role in the ecosystem

Long-term research in Shark Bay, Australia, has shown that tiger sharks control their prey mainly through fear. When tiger sharks are present, dugongs and green turtles avoid the richest, most exposed seagrass patches and keep moving, which prevents overgrazing and keeps the seagrass meadows — and everything that depends on them — healthy. Remove the sharks and the meadows degrade.

Reproduction and life cycle

Tiger sharks are ovoviviparous: the eggs hatch inside the mother and the pups are nourished by a yolk sac until birth. Litters are large, from 10 to 80 pups, each about 50–75 cm long, born fully independent after a pregnancy of around 15 months. Females may breed only every two to three years, and tiger sharks grow slowly and mature late, which limits how fast populations can recover.

Threats and conservation

The tiger shark is Near Threatened and declining. The main pressures are:

• The shark fin trade — tiger shark fins are large and valued.
• Bycatch in longline and net fisheries.
• Shark control programmes — the baited hooks and nets set off popular beaches in Australia and elsewhere kill large numbers of tiger sharks, along with rays, turtles, and dolphins.

As a wide-ranging apex predator that reproduces slowly, the tiger shark is exactly the kind of species that declines quietly and recovers slowly, and its loss from an area can reshape the whole coastal ecosystem.