Carcharias taurus (aka Grey Nurse Shark)

Description

The sand tiger shark averages 12 feet in length and weighs up to 660 pounds; females are larger than males. The dorsal side is gray in color, the underside dirty white; the distinguishing color features are the metallic brown or reddish spots on the sides. This species is also distinguished by its flattened, cone-shaped snout, and by its anal and both dorsal fins being the same size. The long dagger-like teeth are visible when the mouth is closed, giving the sand tiger shark a menacing appearance.

Distribution and Habitat

Sand tiger sharks are found in coastal areas of all the oceans except for the eastern Pacific. Although it can be found at depths of up to 630 feet it is most commonly seen in the shallower waters of the continental shelf.

Diet

While bony fish make up the bulk of the sand tiger shark's diet, it will also go after a variety of invertebrates, as well as other small sharks. Groups of sand tiger sharks will sometimes hunt cooperatively, chasing fish into small groups and then attacking them.

Reproduction

Mating usually takes place in October and November, and gestation takes 6 to 9 months. The first embryo to develop will usually eat its uterine mates, so that only one or two pups are born (one pup per uterus). Pups are about 3 feet long at birth, and are able to fend for themselves almost immediately. It is believed that sand tiger sharks reach sexual maturity at 4 to 6 years.

Behavior

Sand tiger sharks often travel in groups of twenty or less, but are sometimes encountered alone. They are most active at night, spending the day in a rocky enclave.

This species is unique among sharks in that it will come to the surface to take big gulps of air; it holds the air in its stomach, allowing it to maintain neutral buoyancy, meaning it does not have to keep swimming in order to stay afloat.

Populations in the northern and southern extremes of the range may make seasonal migrations to warmer waters.

Despite its menacing look, the sand tiger shark is not aggressive. It has never been known to attack humans without provocation, and even when provoked is more likely to shy away than fight back.

Conservation Status

The sand tiger shark has the lowest reproduction rate of all sharks, giving birth only once every two years or so. Because it lives in fairly shallow water it is frequently in danger of being caught in fishing nets. These factors, combined with its erroneous reputation as an aggressive shark, has seriously reduced its numbers in the wild. It is, therefore, listed as a vulnerable species and is protected in much of its range.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Chondrichthyes
order Lamniformes
family Odontaspididae
genus & species Carcharias taurus

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