Sand tiger sharks derived the name from their habitat, which is mainly located towards the sandy shorelines. They are known as gray nurse sharks in Australia, spotted ragged-tooth sharks in Africa, and sand tiger sharks in the United States and the United Kingdom. Even though they have a threatening appearance, these sharks are very gentle and slow-moving. They are not found to attack humans, unless provoked.
The sand tiger shark has a stout body with a slightly flattened head. The snout is conical in shape and the eyes are small. The mouth, which is kept open while swimming, is full of sharp-edged teeth. The dorsal fins are almost equal in size, and are located far behind the gill slits. The upper lobe of the tail fin is longer than the lower one. Most of the individuals are grayish bronze with a pale white underside. Offspring of this shark, sport reddish-brown spots on the tail and the posterior end of the body. These spots fade as they grow.
The length of an average sand tiger shark can range between 1.2 to 2.7 meters, but the longest specimen had a body length of 3.2 meters. These sharks weigh between 90 to 160 kilograms. One of the distinguishing features of this shark, is that they are the only known sharks, that swim to the surface to take in air. They store this air in the stomach, which helps them float.
Habitat and Distribution
Sand tiger sharks are found in all subtropical and tropical oceans. They can be seen in the eastern and western Atlantic, the Pacific and Indian Oceans, and in the Mediterranean and Adriatic Seas. Their habitats include estuaries, bays, rocky coral reefs, and sandy coastal waters. They are mainly found in coastal waters from the surf zone to the depth of 60 meters. They can also swim to the depth of over 200 meters, and have a tendency to rest at the bottom.
Behavior and Food Habits
Sand tiger sharks remain calm and move slowly during the daytime, but become active in night. During nighttime, they move around in groups for predation. Their food includes small bony fish, crustaceans, squids, other sharks, crabs, and lobsters. They are also known to attack full fishing nets.
The males reach maturity, when they reach a body length of 2.1 meters, and females are able to reproduce when they are around 2.2 meters long. The female sharks give birth to two young ones, after a gestation period of 9 to 12 months. These sharks are ovoviviparous, which means that they give birth to young ones from eggs, that hatch within the body. Female sand tiger sharks have two uteri. Many eggs hatch inside each of the uteri, and the offspring feed on one another. This goes on till two pups are left, one in each uterus. This is termed intrauterine cannibalism. The mother shark produces eggs continuously, which provides nourishment to the young ones in the uteri. They have a lengthy labor, usually in winter, and the young ones are almost one meter in length at birth.
The lower reproduction rate among these sharks has led to a decline in their population across the globe. These sharks are now a protected species in countries like, the U.S. and Australia. Conservation efforts are also underway to protect sand tiger sharks, which are the most popular sharks found in aquariums around the world.