Sand tiger shark

800px-Carcharias_taurus_newport

Profile

Sand tiger sharks are medium to large-sized sharks living in many coasts throughout the world. As you can see in the map below, their range includes every continent except Antarctica. They are also frequently found in aquariums. The National Aquarium in Washington D. C. is one of these aquariums. Click here to watch a video about their two sand tiger sharks.  It is thought that aquarium owners gave these sharks their name. Supposedly they used to be called sand sharks, but owners thought the name was too plain and added the word tiger.  These animals are also known as gray nurse sharks and spotted ragged-tooth sharks. Although they look ferocious, partly because their teeth show even when their mouth is closed, sand tiger sharks are not aggressive and therefore are not a big threat to humans. Most sharks are considered very dangerous and “man-eaters,” but most of them, sand tiger sharks included, will normally only attack if they are bothered first. I still think they over-react a little though. As with most sharks, the top part of their body is a dark gray while the bottom part is much lighter. Despite the similar name, these animals are even in a different order than tiger sharks. Sand tiger sharks are nocturnal and they frequently dive as low as 656 feet (200 m) below the ocean’s surface. Sometimes sand tiger sharks have been observed gulping air from the surface and storing it in their stomach in order to increase buoyancy. They are the only sharks known to do this. These fish are also different than other sharks in that their two dorsal fins, the ones on the top of their body, are basically the same size. As with most sharks, they have a sixth sense that lets them detect electric pulses in the water. This helps them find prey.

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Male sand tiger sharks have an average maximum of 8.5 feet  (2.6 m) while the average maximum length of females is 9.8 feet (3 m). As you can see, females are usually slightly larger than males. Although these lengths are normally the maximum, these sharks have been known to be up to 10.5 feet (3.2 m). The average weight of sand tiger sharks is 350 pounds (159 kg) while the maximum is around 64o pounds (290 kg).

Diet

Sand tiger sharks are not picky eaters and consume many different fish including mackerel and flounders. Other food includes squid, lobsters, rays, and even other sharks. They hunt in groups and have been spotted surrounding schools of fish in order to trap them for the attack. They have also been spotted attacking full fishing nets. These sharks do not eat much and the a study on captive specimens showed that they eat only two percent of their body weight each week! For the average 350 pound sand tiger shark, that would be only seven pounds (3 kg) per week! Humans on the other hand eat about two percent of their body weight each day instead of each week! Such a low consumption rate is probably due to the fact that they are slow swimmers and therefore do not need much energy.

Mating and young

Males four years and older and females six years and older mate most of the year except during the summer. Females only mate every other year. After a nine to twelve month gestation period, two live pups are born, one from each uterus. Although there are many eggs in each uterus to begin with, cannibalism occurs.  The young hatch from their eggs at different times and the oldest one starts eating the other eggs and the young that hatch later. During the fall and winter, the two, thirty-nine inch (1 m) long pups are born. The young grow ten to twelve inches (25-30 cm) each year for their first year, and each year the growth rate decreases by about one inch (2.5 cm) per year. Their minimum growth rate is about two to four inches (5-10 cm) per year. In the wild these animals can live for up to fifteen years.

Status and threats

The IUCN redlist states that the sand tiger shark is vulnerable. This is partly due to their low reproductive rate and also to over-fishing. In Japan, the meat of this animal is prized. Their oil is also used world-wide, and their skin is used for leather. Despite protection in many areas, the population of this species is still declining, and it has dropped more than twenty percent in the last ten years.

 

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Sources:

Photo credits:

  • Sand tiger shark – Jeff Kubina
  • Sand tiger shark range – Chris_huh
  • Mystery animal – Andrew c
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