At the beginning of 2021, I had the amazing opportunity to spend a few months in Sodwana Bay, South Africa with Sharklife Conservation Group studying the spotted ragged tooth sharks, also known as Sand Tiger Sharks in the USA and Grey Nurse Sharks in Australia. Carcharias taurus is part of the mackerel shark order, and while there are two other species of ragged tooth, the small tooth and the big eye, they are not as common and more rarely seen.
Sand tiger sharks, not to be confused with tiger sharks, are widely distributed and found near tropical and subtropical coasts worldwide with the exception of the Eastern Pacific and the Mediterranean. The last recorded sighting in the Mediterranean was in 1980, just 70 years after they were first discovered in Sicily in 1910 by Constantine Samuel, making them regionally extinct in the Med. They tend to stay near shore, in waters 3 to 50 meters deep and they prefer gullies and rocky caves to avoid currents. They have a unique ability to hover in the water column by gulping air from the surface.
Every year, portions of the adult population migrate as part of the breeding cycle. This is primarily what our Ragged Tooth research at Sharklife focused on during my duration in ZA. Mating occurs in southern KwaZulu-Natal, then the females move further north into shallower and warmer waters, such as those in the sanctuary where we observed them. We used a variety of survey methods including Baited and non-baited Remote Underwater Video, and Underwater Visual Census with freediving and SCUBA diving to collect raw data on the Raggie sharks and other Elasmobranchs in the area, followed by using computer systems to record, track, and gather information from the data. Like whale sharks, spotted ragged tooth sharks’ spots are unique to the shark and their individual patterns played a vital role in being able to track and record the sharks and their movements. Once the pregnant females have gestated and rested in our waters for about 5 months, they’ll move back south to the Eastern Cape to pup. The gestation period lasts about 9-12 months in total and they are ovoviviparous, which means they give a live birth.
Baby sand tiger sharks are born about 1 meter or 3 feet long. They can grow to 3.2 meters but average 1.8-2.5 meters long. Males mature at 7 years or just under 2 meters while females mature at 10 years or just over 2 meters. Adults are expected to live over 40 years and females have a 2-3 year rest period between breeding migrations.
Sand tiger sharks are sluggish predators that feed mostly at night. Their diet consists mainly of bony fish like herring and mackerel, but they will scavenge and eat small sharks and rays, crabs, and crawfish. Their teeth form limits their prey size to things they can swallow whole. The teeth on both jaws are similar in shape and size - they’re a tricuspid tooth with an elongated blade and no serrations, used as a grabbing tool only. Prey is captured with a sideways lunge attack that impales prey on their large front teeth. The jaw protrudes to enhance the bite.
These chilled out sharks that can only consume bite-sized pieces are listed as Vulnerable on the International Union for Conservation of Nature’s Red List. This means they are facing a high risk of extinction in the wild. Two major threats to spotted ragged tooth sharks aka sand tiger sharks aka grey nurse sharks are handline fisheries and shark culling.
Thankfully, the sanctuary that I talked about earlier is a protected area where fishing and even diving is not allowed. (Sharklife was the exception with our special research permit which allowed us to conduct research - and only conduct research - in the protected area.) However, more than once we had to remind or inform fishermen that they were not allowed in that area and would have to go further to sea where the fishing restrictions were not in place. These sharks are a recreational fishery target caught for sport and trophies and it’s estimated that 1763 are caught each year in South Africa.
Additionally, gill nets and drumlines are installed off of beaches in South Africa, Australia, and New Zealand to reduce the risk of a shark biting a bather. Sand tigers are not a threat to bathers but are incidentally caught in these shark culling programs. An average of 41 ragged tooth sharks are caught in South Africa every year due to these programs, and only about 28% of them are released.
Sand tiger sharks will often be found swimming slowly near the bottom or hovering in caves and overhangs. Many sharks we observed were so slow moving sand had started to accumulate on their backs! They may approach you - just relax! Always wait for the sharks to come to you. Don’t swim after the sharks; this will chase them away. Do not disturb resting sharks; keep a distance of at least 5 meters. Avoid waving your hands around and make sure you continuously look around to be aware of where the sharks are.
To learn more about Ragged Tooth Sharks or to support the research of these magnificent beasts, visit sharklife.co.za