Ragged-tooth sharks, also known as grey nurse sharks in Australia and as sand tiger sharks in the USA, occur in temperate to tropical coastal waters of the Atlantic, Indian and western Pacific oceans. In South Africa they are common along the eastern and southern coasts, occurring as far west as False Bay.
Like all sharks, ragged-tooth sharks have a cartilaginous skeleton. They grow to about 3,2m in length and live for about 30 years. They reach sexual maturity after 5 years, and at approximately 2.2m in length.
Sharks’ teeth are arranged in rows which continually move slowly forward, like conveyor belts. This ensures a constant supply of sharp, new teeth and results in sharks losing and replacing thousands of teeth in a lifetime.
These juvenile ragged-tooth sharks act as ambassadors for their species as we only display them for a short period of time before returning them to the wild. Once they reach a certain size we will release them at Buffel’s Bay (close to the Knysna/Plettenberg Bay area), where other ragged-tooth sharks of a similar age are found. All our sharks are tagged prior to their release.
Ragged-tooth shark migration in South Africa
Ragged-tooth sharks are found on the southern and eastern coasts of South Africa.
In November/December they congregate to mate on reefs in northern Eastern Cape and southern KwaZulu-Natal waters. The pregnant females then travel north as far as southern Mozambique to gestate in warmer waters. After a gestation period of 9 to 12 months, they return to the Eastern Cape (south of the Kei River) to give birth.
Some females only breed every two years.
Using satellite and ultrasonic tags, scientists have been able to gain more detailed information about the movement of ragged-tooth sharks up and down the South African coast.
A violent affair?
Mating in ragged-tooth sharks appears to be a violent affair, as the females are often badly bitten. The reason for this is that the males have to latch onto the females during copulation and they have only their mouths to do so! The eggs are fertilised internally and are enclosed in egg cases in groups of 16 to 23.
The embryos initially feed on internal supplies of yolk. Later they feed on fertilised eggs and on other developing embryos (known as intra-uterine cannibalism). As a result, only two pups are born per litter, i.e. one per oviduct.
The gestation period is 9 to 12 months, depending on the water temperature.
Cartilaginous fishes (including sharks, rays and skates) reproduce in one of three ways.
Oviparous – the female lays an egg case referred to as a “mermaid’s purse”. These are often found washed up along the shore. This egg case contains the embryo and yolk supply and the young shark eventually hatches out of the case. Cat sharks and shy sharks are oviparous.
Ovoviviparous – the embryo hatches from the egg inside the uterus, where it feeds off its own yolk sac until it is born. Ragged-tooth sharks are ovoviviparous. Most sharks breed in this way.
Viviparous – the embryo develops in the uterus and is fed either through a placenta or by uterine milk. Hammerhead and great white sharks are viviparous.
Ragged-tooth sharks are threatened around the world because they are slow to reach sexual maturity, they give birth to few young and, because of their inshore habits, they are highly vulnerable to over-fishing.
Ragged-tooth shark populations have been seriously depleted in Australia and the USA due to over-fishing. In 1984, Australian ragged-tooth sharks became the world’s first protected shark species. Today they are also protected in the USA, while in South Africa they may not be sold commercially without a permit.
The status of the South African ragged-tooth shark population was considered to be “near threatened” by an International Union for Conservation of Nature working group in 2003. However, the actual size of the population is unknown and is currently under investigation.
South coast rock lobster
These deep-water rock lobsters live at depths of between 90 and 170m. Because they are deep-sea creatures, they are only caught commercially using baited lobster pots.
Commercial fisheries catch about 800 tonnes of South Coast rock lobster every year.
Are these lobster, crayfish or kreef? They are not true lobsters because they don’t have large claws. They are also not the same as the fresh-water crayfish found in Europe that do not have such gourmet appeal!
In South Africa we call them crayfish or kreef. Their correct name is rock lobster or spiny lobster.
Shed my skeleton
Like all crustaceans, rock lobsters have a hard exo-skeleton (meaning the skeleton is on the outside of the body rather than on the inside like ours). The skeleton is jointed, allowing rock lobsters to move quickly and efficiently on their 10 jointed legs. Although the hard exo-skeleton is like armour or a bullet-proof vest and protects them from predators, rock lobsters have to shed the skeleton in order to grow. This is called molting. During molting, rock lobsters are soft and vulnerable to predators until their new shell hardens.
Starfish – general information
Starfish have five arms, each with its own set of respiratory, digestive and reproductive organs!
Each arm also has hundreds of tiny tubefeet that enable the starfish to creep slowly over the reef.
Don’t worry if you see a starfish with only four or even three arms. Starfish can regrow their arms – in fact a single arm can regenerate a whole body!
Feeding inside out
The mouth is on the underside and the anus on the topside.
Starfish feed by turning their stomachs inside out and releasing enzymes to digest the food externally. It can take a starfish several hours to pull a mussel apart and slowly digest it.
Spiny sea star
These creatures are common on the rocky shores of the Western Cape.
They are either orange or blue-grey in colour. The spines are surrounded by a circle of tiny white nippers that are used for defence and to keep the starfish clean.
Honeycomb moray eel
Honeycomb moray eels are widespread throughout the world, from the eastern coast of Africa to the Great Barrier Reef in Australia.
Common platanna (african clawed frog)
These “flat frogs” live in natural water-bodies, but you might see them in your garden pond. They also don’t mind living in the local sewerage works. At the end of the rainy season, they bury themselves under wet mud, where they hibernate until the next rains.
Also known as African clawed frogs, these “flat frogs” have powerful back legs and sharp claws on three of their toes. They hold prey in their mouths and tear it with an overhead “kick” by their back legs.
Common platannas feed in the water on any living creatures they can overpower. Their prey includes frogs and tadpoles (including their own kind), insects and other invertebrates (mosquito larvae are consumed by young frogs), small fish, young birds and mice that fall into the water. They even feed on carrion in the water.
In the 1930s, it was discovered that a female common platanna would spawn if injected with the urine of a pregnant woman (the hormone chorionic gonadotropin being the active ingredient). In the 1940s and ‘50s, this was the only available pregnancy test and many hospitals around the world kept and bred platannas so that they could perform such tests.
Western leopard toad
The Western leopard toad uses camouflage to blend into its environment and hide from predators.
The Western Cape is the only place in the world where you will find Western leopard toads.
They live in natural vegetation, on farms and in compost heaps in gardens, but move to water, especially wetlands, to mate and lay their eggs.
Keep your eyes open for Western leopard toads on the roads particularly in August when they are breeding and in November when the young toads are making their way from the water to land. Please brake for the toads!
The snoring toad
Male Western leopard toads start calling in early spring – their call sounds just like loud snoring! When you hear them calling you will know that they are about to start moving towards water, where they will mate and lay their eggs.
Many Western leopard toads are killed during the breeding season as they have to get through or over garden walls, pavements and roads to get to their breeding sites near water. If you see a toad on the road, please pick it up and put it on the other side of the road (in the same direction in which it was going).
Teddy, the tongueless toad
This Western leopard toad, named Teddy, was found at the South African Astronomical Observatory (SAAO) after nature conservation staff based at Kenilworth Racecourse received a call from a concerned SAAO staff member, reporting an injured toad with its “tongue hanging out of its mouth”. Conservation staff rushed to site and found the toad in a terrible condition. He had most likely been hit by a car and was very thin. He had a broken lower jaw bone, a protruding upper jaw bone, several wounds on his head, severe damage to both eyes and a tongue that was red, swollen and hanging out of his mouth.
Teddy was slowly nursed back to health by conservation officials, but his tongue was so badly damaged that it had to be amputated. His injuries also resulted in blindness in one eye and partial blindness in the other. Initially he had to be force-fed as he did not know how to catch food without his tongue, but he quickly learned to grab prey and now feeds on his own.
Teddy cannot be released back into the wild, but will remain at the Two Oceans Aquarium as an ambassador for his species. Toads face great danger from cars and people and many are killed or fatally injured. We plead with every person reading this story to take care when driving and watch out for toads and frogs on the roads! The future of frogs is in our hands!
This is a temporary exhibit. It is not easy to keep frogs in captivity as they are easily infected with disease and parasites. Although it is not policy, CapeNature has given the Aquarium special permission to display these frogs in recognition of the Year of the Frog.
Northern rockhopper penguin
Rockhopper penguins are the smallest of the crested penguin species. They live on rocky, inaccessible coasts and are renowned for their jumping ability.
Anemones are simple animals that look like delicate flowers. But these “flowers” can move and catch prey.
Anemones have poisonous barbs in their tentacles that fire on contact, injecting poison into their prey.
To protect themselves, anemones secrete a special slime that prevents the stinging cells on one tentacle from firing when they come into contact with other tentacles or with the anemone’s body.
According to Two Oceans: A guide to the Marine Life of Southern Africa (Struik, 2007), the common octopus lives at depths of up to 200m and feeds on crabs, shellfish and rock lobsters. It lives in crevices and holes and is fiercely territorial.
Longnose butterflyfishThe longnose butterflyfish is easily recognised by its yellow body and black and white head, but its most remarkable feature is its long snout. It uses this long snout to probe crevasses for food particles and prey, and to bite the tube feet off of sea urchins and other echinoderms. The longnose butterflyfish is the most widespread species of butterflyfish. It lives in pairs along rocky shores and reefs along the southern African coast. It is a common visitor to deep reefs throughout the Indian and Pacific Oceans. It is highly territorial, and will defend its patch of coral from any other longnose butterflyfish of the same sex. This butterflyfish uses soundwaves, generated by body movements, to signal its territorial boundaries to other fish. The IUCN classification for this species is Least Concern with stable populations
Pearly butterflyfishPearly butterflyfish have very distinct colouration - silver-white bodies, yellow hindquarters and black chevron stripes pointing towards their heads.They inhabit sea-facing reefs off the east coast of Southern Africa, where they hunt small invertebrates and scavenge scraps of seaweed.The IUCN status is Least Concern.