Sand tiger sharks look very ferocious, with a row of jagged teeth that you can see even when their mouths are closed! However, these fish are not very aggressive toward people. They generally bother people only when people bother them first. Sand tiger sharks have possibly the oddest method of reproduction in the shark family. This shark is ovoviviparous, meaning that its eggs hatch inside each of the mother's two uteri and are later born live. The largest sand tiger embryos in each uteri gain nourishment by eating their smaller siblings. This mode of survival, called intrauterine cannibalism, results in two large healthy pups that are about 3 feet in length when they are born. Sand tiger shark populations have declined by more than 20 percent in the last 10 years and they are listed as a vulnerable species in the Atlantic Ocean. The sand tiger, also known as the gray nurse shark or the spotted ragged tooth shark, poses little danger to humans.