It takes a lot of courage to come face to face with a menacing mouth full of teeth. Yet every year hundreds of local and overseas scuba divers, regularly stumble upon ragged-tooth sharks. They are a common sighting on certain reefs on the East Coast of South Africa, particularly at Aliwal Shoal and Protea Banks.
The Southern Hemisphere winter time brings this migratory species to these shallow waters in search of large rocks or cave formations that provide calm shelter for mating. After a couple of months, adults will move north towards warmer waters like Sodwana or Rocktail Bay in Mozambique, where the females gestate in the shallow waters. These sharks have a variable gestation period which can last between eight to twelve months. Once ready to give birth the sharks travel to the southern tip of South Africa where they give birth in the cooler waters. Young adults and juveniles born in previous years sometimes tend to stay in warmer waters longer and can sometimes be seen in Aliwal Shoal towards end of summer. This all-year-round migration provides plenty of opportunities to see them in many locations on the Southern African coast – however the best time for encounters in large numbers is during winter.
Ragged-tooth sharks, or locally called ‘raggies‘, are a treat for any passionate nature-lover as, unlike most other marine creatures, they move at a sluggish pace, hovering slightly above the seafloor. However, while hunting they can be incredibly fast, but they hunt at night so as a scuba diver you are most likely to see them resting.
Fortunately they have no interest in divers, although they are dangerous animals so caution is advised when approaching. Ragged-tooth sharks’ strange dental structure, as seen in the picture below, means that they are unable to sheer large chunks of flesh from their prey as they lack a straight cutting edge. Instead these sharks eat fish whole, held in place and killed by their multiple rows of ragged teeth! Humans are far too large to be perceived as prey and we are too small to be predator, so they tend to ignore us underwater.
One of the best places to see raggies is off a famous dive site in Aliwal Shoal called the Cathedral. It is a massive amphitheatre of coral rock about 10 metres in diameter, and roughly the same height, and the sharks tend to congregate here.
Divers can wait near the seafloor and get a wide view of up to a dozen or more sharks slowly circling in this semi-open cave. It is quite a sight to behold as not many can say they have had the chance to be so close to so many large, formidable predators and yet be completely safe.
Facts about ragged-tooth sharks:
1. They are the only shark species to gulp air from the surface and store it in their stomach to maintain neutral buoyancy allowing them to hover in one place.
2. Females can accommodate many embryos that initially grow feeding off their yolks. However after consuming all the yolk, the largest embryo starts to eat its siblings in a process called intrauterine cannibalism. When the largest embryo grows to about one meter in length the female gives birth to it. This process then gives the final shark a much higher chance of survival.
3. They have varied regional names. In South Africa they are known as ragged-tooth sharks whilst in Eastern Australian they are called grey nurse sharks and the Western Atlantic population is often called sand tiger sharks.
4. These sharks can reach up to three metres length and 150kg in weight.
Watch the below video on the ragged-tooth shark, part of my Creatures of the Sea series: