on the Run
by Wolfgang E. Grulke
by Wolfgang E. Grulke and Marc Montocchio
do you fear most in the sea? What gives novice divers the biggest adrenaline
a South African diver has encountered a shark it will almost invariably have
been a 'raggie'!
The spotted raggedtooth shark Carcharias
taurus is known by many names around the world - the 'raggie' or ' spotted
raggedtooth shark ' in South Africa, the 'sand tiger shark' in the USA and New
Zealand and the 'grey nurse shark' in Australia. The Latin names appear equally
confused! In just three current in-print tomes on 'The Shark' you can find these
three varieties: Eugomphodus taurus, Carcharias
taurus and Odontaspis taurus!!! Carcharias
taurus seems to be the current 'most correct' version to use! However, this
is one shark that is feared much more for its looks than for its actions.
The picture above was the result of a somewhat unnerving experience with
a raggedtooth shark. It had been rough weather that day and visibility on the
reefs had been poor with persistent surges churning up the sandy bottom.
However, we heard that several sharks had been sighted on a reef close to shore
and we could not resist the temptation to take a look.
We quickly dropped down onto the shallow reef from our boat and
immediately saw a number of large sharks drifting in and out of our limited
field of vision. We had dived with raggedtooth sharks before and knew them to be
shy and timid if not provoked. I ventured out onto a flat sandy patch across
which the sharks appeared to be circling consistently. I was kneeling on the
sand and took a few photos of sharks swimming above me. Suddenly a particularly
large shark swam directly at me. Rather than veering off about a metre ahead of
me (which would have been the expected behaviour) this shark just kept coming -
straight at me, ever so slowly!
Eventually, there I was, bent over backwards, still roughly in a
kneeling position but with my back arched back onto the sand, with the shark
swimming directly over me. My mask was no more than 10 centimetres from its
belly and I had to pull my camera and its wide-angle lens right against my chest
to prevent the shark from bumping into it! Then I remembered that I should
perhaps release the shutter! The picture above is the result. Despite the
scatter from the flash in the sandy water it will eternally capture the 'raggie'
experience perfectly for me!
The raggedtooth shark has a truly fearsome visage - a wide mouth simply
bristling with sharp protruding dog-like teeth! The edges of the jaws contain at
least five concentric rows of teeth, embedded in connective tissue stretched
over a cartilage jaw. Each of the inner teeth ever moving forward within the
connective tissue to replace those older teeth lost at the front - more than
1000 in a lifetime of around 15 years.
The raggedtooth shark mostly appears sluggish in the water but can
display amazing agility and speed when hunting. It feeds almost entirely on
fish, small sharks and squid which are impaled on its prominent teeth before
being swallowed whole.
In South Africa the raggedtooth shark is one of the most common sharks.
It's life cycle is an epic story of continuous voyages up and down Southern
Africa's rugged east coast. A rough coast washed by huge swells that come from
deep in the Indian Ocean. A coast unsheltered by fringing reefs and exposed to
everything the sea can throw at it. For the raggedtooth shark it is a life lived
in almost constant travel, up and down the coast from the eastern Cape to the
southern reefs of Mozambique, around Inhaca island..
Each spring the mature females migrate from the colder eastern Cape
waters around Plettenberg Bay and St Francis Bay into the warmer waters of
KwaZulu Natal to mate. Mating appears to be a passionate and somewhat violent
affair as the females emerge with significant scars, apparently inflicted by the
males during courtship and mating. You will not be surprised to learn that while
many male sharks, easily identified by a large pair of claspers, have evolved
longer teeth, the females have evolved a thicker, tougher skin to protect them
The exact whereabouts of the population of male raggedtooth sharks
before, during and after mating still remains much of a mystery. Many are
believed to spend much of their time in the eastern Cape but there is little
hard information to go on. The shark nets around the popular bathing beaches are
amongst the best indicators of their movements.
After mating the female sharks continue their migration north. By
midsummer (December/January) the large pregnant females are found on the close
inshore reefs of Maputaland (where the accompanying photographs are taken) and
southern Mozambique. The warm waters of these shallow reefs are believed to
stimulate the development of the embryos.
During this 9-month period of gestation, the female sharks hardly feed
at all, seriously depleting their energy reserves. Sometimes, as a result of
this inactivity, hydroids can be seen growing from their mouths, in between the
razor sharp teeth, while they are 'parked off' at Sodwana Bay.
Each mother produces masses of eggs (more than 20 000 were found in one
shark), each one packaged in tiny parcels with about ten others, making hundreds
of small egg bags, in each of her two uteri. Many of these eggs are fertilised
embryos. The embryos that develop first have an unfair advantage over the others
and use the egg parcels as a food supply, consuming both the unfertilised eggs
and the fertilised embryos. It literally consumes its own siblings - until only
one shark is born from each uterus. This process of intra-uterine cannibalism is
called oophagy and represents natural
selection with a vengeance - and even before birth!
They must make the long journey back to the Eastern Cape waters, riding
the warm Agulhas current to conserve energy, before they drop their young in
mid-winter (July/August). At birth the raggedtooth sharks are each about a metre
long and weigh around six kilograms and fend for themselves almost immediately.
At first limp and unable to swim, they take about two hours to tone up their
swimming muscles and stiffen the fins, and then face whatever the marine world
will through at them. The mothers show no parental care, as is the case in most
other lower vertebrates.
The mothers, starved from months of abstinence, leave the area
immediately after pupping to avoid feeding on their own offspring. It is believe
that they take a break of at least a year to replenish their energy reserves
before another maternity cycle begins.
The juvenile sharks make their journey up the coast and are often seen
at Aliwal Shoal, south of Durban on the eastern Kwa-Zulu Natal coast, during
July and August each year.
Thankfully, the raggedtooth shark displays an almost nonchalant
indifference to divers. As long as they are responsibly observed they appear to
share even close proximity readily with divers. This tolerance of divers has
contributed a great deal to our understanding of shark biology and behaviour.
When with them, I always find the temptation to touch and stroke enormous, but
have resisted my entire life. I know that a simple flick of the tail from a
surprised shark could easily result in death of a nearby diver.
To experience these sharks in their own environment is always a majestic
experience - whether itís the raggie juveniles at Aliwal Shoal or the serene
mothers-to-be at Sodwana Bay's Quarter-Mile Reef. You can sense the power of
those bodies and jaws just an arm's length away. At any point they could choose
the act less accommodatingly to the diver. Thankfully, this is not part of their
majesties' behaviour! A majestic experience - yet humbling! Wherever you find
the raggedtooth shark, the sandy gullies in the area are always likely to yield
a few dropped teeth! A wonderful opportunity to take back to earth a souvenir -
just to make sure you weren't dreaming some kind of crazy dream!
Thanks to Geremy Cliff of the Natal Sharks Board in Umhlanga Rocks, Kwa