Hooked: Neil Burnie of the Bermuda Shark project attaches a satellite tag to one of Bermuda’s many tiger sharks. *Photo by Chris Burville
Hooked: Neil Burnie of the Bermuda Shark project attaches a satellite tag to one of Bermuda’s many tiger sharks. *Photo by Chris Burville

WEDNESDAY, JUNE 15: Tiger sharks are navigating between Bermuda and the Caribbean with the speed, accuracy and precision of a GPS-fitted mega yacht.

Research on sharks tagged in Bermuda suggests they could be using sophisticated “mental maps” to roam the ocean, swimming huge distances between their favourite spots.

A location map of the 30 sharks tagged on Challenger Banks over the past three years shows pin-points scattered across the western Atlantic.

But a closer look at the tagging data shows how the sharks utilize “home ranges” spanning thousands of miles of ocean between the Bahamas and the deep ocean around Bermuda.

Despite their expansive migratory habits the sharks are able to pinpoint exact locations in the ocean and time their arrival almost to the day.

Record breaker

One shark, named Correia after the company that sponsored its satellite tag, has provided more than two years of consistent data — the longest satellite track ever recorded for any shark anywhere in the world.

It was clocked arriving in the Bahamas on almost same date each year for the past two years.

A second shark “Harry Lindo” has arrived at the same point in the Bahamas on the same day for the past two years.

The information, from tags fitted by Neil Burnie and Choy Aming of the Bermuda Shark Project, is providing US-based scientists with a slew of new data.

Researchers from Rhode Island University and Nova South Eastern University in Florida are using the information to help solve unanswered questions about shark behaviour.

Mr Aming, said the shark project — which started as a hobby for him and Mr Burnie — had answered some of their original queries.

But he said it had posed a whole host of new questions.

“When we started this we weren’t sure what we would find.

“All we knew was what local fishermen had told us — if you go to the banks in June and July you might find a tiger shark.”

He said the project had established that the sharks found on Challenger Banks in the summer months appeared to be Bahamian sharks that summered in Bermuda.

And he said the information from the tracks was fuelling new questions about how they navigate.

“We’re not sure — do they have mental maps of their home ranges that they are following?

“Could they be using some form of inner compass to navigate huge distances using the earth’s magnetic field?

“Are they operating in an optimal temperature range and moving north towards Bermuda as the water gets warmer in the islands?

“Are they using the geography of the ocean floor to navigate to favourite feeding grounds?”

A total of 30 sharks have been tagged over the past two years, through funding from local sponsors Masters, Lindo’s, Kitson Group, Correia Construction, Crisson Construction, Endsmeet Animal Hospital, Miles Market, Geoff Griffiths, the Atlantic Conservation Partnership and the US based Guy Harvey Research Institute.

Three juvenile sharks, tagged last year, threw up an interesting quirk in the data — staying around Bermuda for the entire year.

Making headlines

“One of the aims for this year is to tag a couple more juveniles and see if there is a pattern there,” said Mr Aming, who previously made headlines for riding on the back of a tiger shark and has made an acclaimed documentary about the work of the Bermuda Tiger Shark Project.

“All of our data is being fed to our research partners in the US. They have some researchers and a couple of grad students working on it.”

He said researchers were combining the information from the Bermuda study with data from other tagging projects around the world.

“There are still so many unanswered questions and we are playing a big part in answering them.”

• The Bahamas is their home — The vast majority of the tagged sharks spend up to seven months a year in and around the Bahamas before heading north in June, July and August.

• Sharks don’t need maps — The data from satellite tags suggests sharks can pinpoint their favourite cove in the Bahamas and time their arrival from thousands of miles away to the exact same day each year.

• Sharks can move — It takes just eight days for a tiger shark to travel from Bermuda to the Bahamas — based on the information from the tagged sharks.

• Bermuda is a bachelor pad for sharks — All but two of the 30 sharks tagged in Bermuda’s waters have been male. Researchers hypothesize that females are more territorial, confining themselves to smaller ranges.

• Sharks don’t come inside the reef (most of the time) — Scare stories of tiger sharks cruising off the beaches aren’t backed up by the data. The 30 sharks in the study have made more than 7,000 location transmissions over the past two years. Only two were from inside Bermuda’s reef line — once at South West Breaker and once halfway between Chubb Head and the shore.

• Tiger sharks travel vast distances — All the sharks were tagged within a ten-mile radius of Challenger Banks over the past two-three years. They have since scattered across the western Atlantic. The furthest south was clocked near Cuba. The furthest east recorded its location at the
Mid-Atlantic ridge.

• They are not as ferocious as they seem — No one’s denying that tiger sharks are potentially dangerous animals. But both Neil Burnie and Choy Aming and scores of volunteer helpers have spent countless hours in the water filming them and recording their behaviour. Mr Aming believes that they are not as dangerous as movies and Discovery Channel documentaries would have us believe.

• Sharks don’t worry about hurricanes – The shark oil may go crazy during a hurricane but the sharks themselves don’t seem to mind. During Hurricane Igor several of the tagged sharks were breaking the surface regularly — even as 30-foot swells rolled across Challenger Banks. Unlike whales, sharks have no need to surface, so the fact that they do so is mystifying.

• Sharks occasionally work together – Long thought of as lone hunters, footage recorded by the Bermuda Shark Project Team suggests that tiger sharks can and do work together.

One stunning clip shows two sharks, who the team christened ‘the brothers’
taking turns to attack a marlin-head (used as bait) while the other protected it from rival predators.

• They’re big…but they’re not monsters – The mythical 20-foot beast remains a myth. The average size of the tiger sharks (recorded from the nose to the fork of the tail) tagged in Bermuda is nine-feet. The smallest was a six-foot juvenile and the largest an 11-foot adult.