Tracking study reveals secret life of great white sharks
Great white sharks are on the prowl around the clock, so the old rule about staying out of the water at dusk and dawn no longer applies.
But, while researchers tracking the species as part of the five-year state government Shark Management Strategy have found the sharks lurking around beaches at all hours, they say the vast majority are simply being "nosy".
The finding is among a raft of discoveries scientists have made during one of the most intense air and sea studies of great whites in Australia in the wake of a series of fatal shark attacks on the NSW coastline.
With almost 470 sharks tagged and tracked since the strategy was implemented, NSW
Department of Primary Industries shark biologist Dr Paul Butcher said the research will help improve the management of the species and better protect swimmers.
As well as being incredibly curious, researchers have also discovered that great whites appear to migrate, leave the coast once an adult and are predominantly found near "balls" of bait fish.
And, while they like hanging around beaches, they bizarrely do not spend any time at Port Macquarie.
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That is not the only mystery - despite closely monitoring the species, scientists are yet to learn where the great whites mate and give birth.
Dr Butcher said the remaining questions would form the basis of the next round of research into the little-known species.
"What we do know is that they can be present at any time of day," he said.
"Our tracking has shown they are around at any time.
"Certainly, there are a number of animals specifically up Evans Head, Lennox Head. White sharks are always off our beaches in the period between May and December and we have just to be aware that those animals are around."
If a great white is spotted close to shore, scientists said its curious nature means it is probably taking a closer look at something of interest, such a floating piece of rubbish or a passing sting ray.
"From the drone research that we are doing, the animals travel at speeds of around three to five kilometres an hour near our ocean beaches and they are certainly inquisitive," he said.
"They will investigate everything in the water. They will look at rubbish, seaweed, swimmers. They are inquisitive and curious."
Possibly the greatest finding in helping the future management of the species is great whites follow a coastal migration pattern, moving towards cooler waters from Queensland to Tasmania.
"We are actively tracking 450 sharks right now - we tagged 469, but some are gone - and we have a large array of receivers around the place so we have a good idea where they go," Dr Butcher said.
"We have found they move at predicted times. March to June, they begin moving north from
Tasmania and Victoria where they have spent summer. As the water cools down along our east coast, as the East Australian Current slows down, they start to move back up the coast," Dr Butcher said.
"Then they start moving south between September and December and January."
But while most great whites travel north and south seasonally, some individuals broke from the pack to embark on epic solo journeys to sub-Antarctic waters, off the coast of Papua New Guinea, New Zealand and Perth.
Not only will longer-term tracking help determine why these sharks are swimming off course, it may also help unlock one of the bigger mysteries about the animals - where they give birth.
"Nobody knows where the east Australasian population breed. That's one of the questions.
"A lot of our bigger animals head over to New Zealand. Over the next couple of years, we hope to see where they go. It would be a guess they breed in New Zealand but we just don't know."
What researchers do know is that the adults - sharks of five to 6.5 metres in size - do not hang around NSW.
"We mainly have those that are an average size of 2.5 metres. We've had a handful in the three-to-four metre range and but only two over four metres," Dr Butcher said.
"White sharks rely on predominantly on mammals such as seals as their major good source and the NSW coastline doesn't hold large numbers of those of prey animals so the sharks that we see tend to be in the juvenile and subadult range."
Despite the findings, Dr Butcher said there was still a lot to learn about the species.
Researchers recently finished a project using specialised transmitting tags to collect water temperature, light and depth information from a shark every three seconds.
He said this research would allow for researchers to predict the types of environmental conditions that sharks preferred at different times of the year.
As for what final advice he would give swimmers: "Avoid bait balls".
"We never want to stop swimmer from going in the water. They just need to be aware that they are around."
TRACKING 'SHARK 28'
Researchers will only call him "Shark 28" but it seems he's the great white equivalent of Forrest Gump.
While most of the 450 tagged sharks have been hanging out along the east coast, Shark 28 has been going off on his own solo epic swims around Australia, reminiscent of how the Tom Hanks movie character went running across America by himself. Since the 3m male was caught and released off South Ballina Beach on the state's north coast in July 2016, he has covered almost 40,000km swimming between Queensland and Western Australia via the Great Australian Bight.
During one 307-day swim from Queensland to WA, the shark spent 211 days hanging around The Bight.
Shark 28 was last detected on February 25 in waters near Rottnest Island.
While he may have clocked the most kilometres, his fellow solo traveller "Shark 41" ventured farther abroad.
After being tagged in Ballina in August 2016, the great white was detected in the Bass Strait, Bondi, both the South Island and North Island of New Zealand, Papua New Guinea and down in sub-Antarctic waters. Another great white known as "Shark 179" also went abroad, swimming up to New Caledonia via New Zealand before researchers lost track of it.
The shark reappeared seven months later in sub-Antarctic waters northwest of Chatham Island.
NSW Department of Industries shark biologist Dr Paul Butcher said it was not known what was driving some sharks to break away from their mates to embark on these epic solo journeys.
"At any given time, we've had animals off the coast of New Caledonia or New Zealand," he said.
"Future research may look at the genetic difference between those that do and those that don't to find out what is driving them."