The IUCN/SSC Shark Specialist Group
Shark News 11: July 1998
|
Testing the Shark POD
Valerie Taylor, New South Wales, Australia
In January 1992, Ron and I began a series of tests on a newly designed
electronic device that was claimed by the Natal Sharks Board to repel
sharks. The invention produced a pulsing electronic field that interfered
with sharks' sensitive electro-receptors, creating an unpleasant but
harmless irritation.
Our first tests took place in the Durban Sea World shark tank, in
South Africa. The director of the Natal Sharks Board, Graeme Charter,
was interested in having a diver testing the repeller against potentially
dangerous sharks, underwater.
At first we were both sceptical: in the past we had tested many
different shark repelling inventions. With the exception of the power
head (an explosive device on a spear), which killed the shark, and the
steel mesh suit, which worked well with small to medium sized sharks,
nothing else tested by us had worked.
Along with two raggedtooth sharks Carcharias taurus and a huge
sawfish Pristis sp., three large bull or Zambezi sharks Carcharhinus
leucas were living in the Durban tank. I was to test the device against
the bull sharks, who showed a keen interest in our presence. I stood
against the wall while Ron, with his back against a cage, filmed from
the centre of the tank. Every time I switched on the electronic repeller
the shark would flick away, returning to normal behaviour when the
device was turned off, or it had swum out of range. (The radiating field
has an effective range of 4-5 metres.) The most dramatic results
occurred when I delayed activating the device until the shark was at
its closest (1 metre away). This produced a very rapid departure. When
the device was constantly working, the sharks stayed further away.
They would retreat rather casually to the far end of the tank as soon
as they detected any irritation. During our later experiments in the
tank, we had the bull sharks, jaws agape about to take a fish, suddenly
jerking away when they encountered the pulse.
It was pretty exciting stuff, so exciting that we decided we should
try the repeller against white sharks Carcharodon carcharias in the
open ocean. Ron felt that would be the ultimate test, stopping a great
white when it is homing in on a meal. If the device could turn a great
white, he felt it would probably turn all other shark species.
Ron chose an island with a large sea lion colony for the white shark
tests. Along with shark experts from the Natal Sharks Board, who had
invented the repeller, we travelled to Dyer Island near Cape Town.
Leonard Compagno, the worlds' most knowledgeable shark expert,
accompanied us.
We attracted sharks almost immediately there were baits in the
water. Our surface testing, which consisted of floating out a bait, then
activating the electric field as the shark was about to take it, proved so
successful that we decided we could dive and film these sharks
without the protection of a cage (we did not have one at the time). Two
South African divers accompanied us, one as a safety diver and the
other as second cameraman. We spent two weeks working with the
Dyer Island great whites.
A free-swimming diver, Ian Gordon, is approached by a great white shark while his Shark POD is
inactive.
|
Ian switches on the Shark POD, and the shark immediately turns away. Both photographs are video stills taken from the Taylors' SHARK POD documentary.
|
So successful was the effect of the repelling device, we were able
to do all our underwater filming swimming free in the water with the
sharks. This was something that had never been done before. We felt
invincible after that first dive. There were a dozen or more sharks
around, of which five appear on film, and they all kept their distance.
Following this most successful and exciting experiment, we begin
a series of tests with different shark species back in Australia. Even
when the area was baited, the repeller never failed to turn the
sharks away. All these tests were recorded on film.
Based on the success of this early testing, the Natal Sharks
Board created a separate company to develop a repeller suitable
for divers to wear as protection while swimming in waters where
sharks could be a problem. At first, we tested a prototype while
filming great whites off South Australia. This gave us a great thrill;
once again we found ourselves working outside the cage. The
Shark POD (short for Protective Oceanic Device), as the repeller
was now called, continued to work well, never failing to turn the
shark when it came too close. Ron and I decided that a good TV
documentary could be made about this latest testing. It was history
in the making; we felt it would be of immense interest to divers and
the general public.
After South Australia, we took ourselves into the Coral Sea
where we knew we would encounter several species of sharks. The
dive charter boat, "Spoil Sport" loaned us a rubber boat of our own
to work from, well away from the other divers. This proved to be
a most interesting and action-packed experience. There was no
shortage of sharks and we would have two or three species circling
at a time.
It was during these experiments that we first noticed the sharks'
eyes twitching in tune with the electric pulse emitted by the POD.
We also discovered that, unlike the prototypes we had used in our
earlier tests, once the sharks were feeding they showed a serious
reluctance to stop even though obviously affected by the pulse
(eyes blinking, mouth twitching, gills cramping). The POD would
stop them approaching the baits, but when turned off to let them
get their teeth into the fish, then reactivated, they would not
release the food. This unexpected lack of reaction was a worry,
particularly for the inventors back in South Africa. Once they
released the bait, we could keep them from returning, but switch
off the POD and they would be back into the food in seconds.
By now we had done well over 100 separate tests on at least ten
different species of shark. It was time to hunt for that well known
'man eater' of tropical waters, the tiger shark Galeocerdo cuvier.
We travelled to North Queensland where a friend, Shane
Down, took us out to work with a group of tiger sharks he had been
studying for several years. The location was a shallow lagoon well
off shore, heavily populated by stingrays, a favourite food of the
tiger shark.
The sharks were quickly attracted to our stingray baits. Once
they started to feed, we conducted a series of tests. Marine
biologist Ian Gordon, a specialist in shark behaviour, assisted with
the experiments.
As expected we found the pulse would stop the tigers taking
the bait, but turning off the device so the tigers could started
feeding, then reactivating the POD while they had food in their
mouths had little effect. They could not be stopped from feeding
once they were on the baits. If the tigers released the bait, even for
a few seconds, the activated POD stopped them continuing to
feed. They would circle, obviously wanting to return, but the
radiating electric field would keep them away.
During these tests, lemon sharks Negaprion acutidens, a great
hammerhead Sphyrna mokarran, a whaler Carcharhinus
amblyrhyncos, and a tawny shark Nebrius ferrugineus came to the
baits as well as the tigers. We had the same experience with all of
them. Only the big Queensland grouper Epinephelus lanceolatus
was unaffected. Whether POD was on or off, the big fish continued
to eat some of the bait.
These experiments reinforced our feeling that once a shark
starts eating, the desire to feed overrides the instinct of self
preservation. No matter how unpleasant the irritation of a POD, it
will not release its meal.
The latest POD is a battery powered device which generates a
pulsing electric field between two electrodes. One terminal is on
the diver's tank and the other on the diver's fin. Sharks have ultra-sensitive
electro-receptors with which they can detect the minute
electric fields generated in the muscles of marine life. The pulsing,
radiating fields around the POD irritate the sharks' receptors,
forcing them to move away.
Humans, along with most other forms of sea life, due to their lack
of sensitive electro-receptors, are not affected by the electric field.
With over 40 years of diving, you would think Ron and I had
seen all the amazing things, had all the greatest adventures, but
after making this documentary, I realise we have only just scratched
the surface of our adventure with the sea and its amazing inhabitants.
We did things believed impossible ten years ago that will probably
become commonplace in the next ten months. However, extreme
caution is required when diving with potentially dangerous sharks.
These Shark POD tests, conducted over a period of five years,
have been another tiny step towards a better understanding of that
amazing other world that covers two thirds of our planet and I for
one feel privileged to have been given the chance to take it.
Our hour-long documentary SHARK POD (from which the
video stills illustrating this article are taken) won the Jury award at
Antibes, in France. It is now screening on television, world-wide.
Valerie Taylor,
New South Wales, Australia.
E-mail: taylorvr@ozemail.com.au
Fax: +61 2 9417 4200
|
|
|
|
|
