Great white sharks are found throughout the world's oceans, prompting many beach communities to build special nets to protect swimmers and surfers. But authorities in Cape Town, South Africa, are trying a different approach. They have created a network of shark "spotters" who sound an alarm when danger lurks. The program tries to protect people and sharks. For VOA, Terry FitzPatrick reports.
If you are swimming along Cape Town's ocean beach, this is a sound you do not want to hear.
This is just a test. But about 50 times a year this horn, and an even louder siren, signal an actual alarm. It means a great white shark is swimming toward shore.
Yvonne Kamp of the Cape Town shark spotter patrol says the warnings work.
"It really just takes a few minutes. That siren goes and everybody knows the drill. The shark spotters also walk up and down and whistle and wave hands, whatever it takes to get the last people out of the water," said Kamp.
The shark spotters are a team of 20 specially-trained lookouts. Their work begins not on the beach, but in the mountains high above shoreline.
"Muizenberg beach watch from Muizenberg mountain watch," said Tracey Provins, who peers at the ocean, using high-power binoculars.
"Visibility is about 10 percent. I've got about 20 surfers and 10 bathers, copy," said Provins.
Provins says a great white shark is hard to miss. They can grow up to six meters long.
"It's a dark shadow. Most of the time, they don't come up. If they come up, we'll just see the fin," added Provins.
Provins uses a walkie-talkie radio to warn the beaches below. She tracks everything in the water because wherever there is prey, predators follow.
Great white sharks are a particular problem in Cape Town. At least 250 of them come to feed at seal colony that lives on an island close to shore.
Alison Kock from the University of Cape Town has been using underwater radio beacons to study the sharks. The beacons look like thick grey pencils with fish hooks at the end.
"And what we have here is a acoustic monitor. And, what these do is they work with a transmitter, which we tag the sharks with," she said. "So when we get up close and personal with the sharks, we try to attach these transmitters to them. And, this transmitter sends out a unique code."
Kock's research reveals that sharks stay away from shore when there are newborn pups to eat at the seal colony. But at this time of year, sharks rove closer to the beach in search of other prey. She says great whites are not man-eaters by nature. But they are inquisitive.
"White sharks are particularly confident, curious animals. They're really interested in people," said Kock. "And for the most part they don't do anything. They swim by, they have a look, they swim by, and carry on swimming."
But with more than 100 teeth, even a curious nibble from a great white can maim or kill a person. Cape Town's shark spotter program began three years ago after a series of attacks. There were calls to cull the shark population. But great whites are an endangered species, and Kock says killing them would damage the marine ecosystem.
"Great white sharks are the top predator in our waters here in Cape Town. So this means that they have a lot of influence on all the species below them. They not only prey on seals, they prey on different shark species, fish populations, rays - all kinds of things," she continued.
Shark spotter Yvonne Kamp says safety nets were ruled out for Cape Town because sharks, dolphins, turtles and whales get tangled in them and die. She says her network of warning stations is a healthy compromise.
"When people's lives are threatened, everyone is really keen on keeping the people safe and not worrying about the sharks. What we're trying to do is find a balance, where we're keeping people safe, but we're also not harming the ocean," said Kamp.
Many surfers and swimmers support this approach.
"People should leave the water first before taking out any sharks. You know, it's their world and they should be left alone," said Joanne Merrett.
"I think the sharks have just as much right to be in the water as we have, and they are entitled to be there," added Stan Mitchell.
Kerry van Graan said "I think if they wanted to attack people there would be more attacks, because there are a lot out there. So, basically, you take your chances."
According to Shark Attack File, a group that tracks incidents worldwide, roughly 90 shark bites are reported each year. On average, six people are killed. But, in Cape Town, the spotters seem to be beating the odds. Since they began protecting ten popular beaches, they have not had a single shark attack.