Four hundred million years of evolution has created the ultimate marine hunting machine, the great white shark.
One-fifth of its brain is dedicated to its sense of smell, enabling it to detect and track prey from several kilometres away, an ability complemented by arrays of electro-receptors and sensory pores, extremely good eyesight and a body designed for both short sprints and ultra-marathons.
It's big, fast and dexterous. Then there are those teeth, those ... jaws (oh, how one word has so much resonance).
Carcharodon carcharias uses its mouth the way we use our hands: it has sensitive teeth, a jawbone filled with nerves and a mouth full of tastebuds, meaning when it bites down on something it can immediately sense whether it's food or something to be spat out.
"I think they are about as perfect a creature as you could get,'' says zoologist, wildlife documentary film-maker and author Alison Ballance, who has recently immersed herself in a book focusing on this animal at the apex of the marine food chain (along with the killer whale).
As a top predator, great white sharks face only one real threat to their survival: from mankind. Sharks are killed both accidentally (a bycatch of fishing) and deliberately (illegal poaching, including selling shark fins for soup; and sport-fishing). Other hazards include pollution and coastal nets to keep sharks away from beaches.
As a recreational diver, Ballance has formed a "great respect and admiration'' for all types of marine inhabitants; yet she is also aware of the reputation of the most famous of all shark species.
"If you ask anyone to name a shark, most people will say a great white, despite there being hundreds of other species,'' Ballance says. "The movie Jaws has a lot to answer for.''
Hence, the motivation to write New Zealand's Great White Sharks: how science is revealing their secrets.
"Great white sharks are one of the world's most impressive and familiar predators, an iconic creature that everyone talks about, but we actually know very little about them.''
The book is based on the New Zealand great white shark project, which began in 2005 and was inspired by ground-breaking work by Australian and United States scientists, who had started electronically tagging the species in 1999.
Tagging has revolutionised the study of great whites. Previously, the shark was thought to be a stay-at-home type, found in cool coastal waters. However, satellite tracking has revealed it to be a migratory predator that travels many thousands of kilometres, from the coasts of various landmasses around the world to the middle of oceans, and can dive to depths of more than a kilometre.
Great white sharks live in most parts of the Pacific, Atlantic and Indian oceans, can be found off the east and west coasts of North America, southern Africa (but as far north as Kenya), Australia and New Zealand, in the Mediterranean and Adriatic seas. They are also found around Japan, Taiwan, and other Asian waters, including one close to the equator, although there is no tracking evidence of a great white shark having crossed from one hemisphere to the other.
New Zealand has two key hotspots for great whites: the Chatham Islands and Stewart Island.
The latter provides much of the detail and narrative for New Zealand's Great White Sharks, as Ballance focuses on two sub-adult sharks, dubbed Nicolas Cage and Pip, by those who tagged them.
"The great white shark project ran for 11 years and I came to it a few years into it. I live with one of the shark project scientists [Malcolm Francis]. Back in 2012 I got an opportunity to join the project team off Stewart Island for two days. I was so impressed.
"I had gone to [publisher] Potton and Burton with the idea of a book pitched at younger readers. I had 11 to 12-year-olds in mind, because I have had some brilliant conversations with kids of that age.
"And the subject of sharks is a really good way into science,'' Ballance explains, adding New Zealand's Great White Sharks will appeal to anyone with an interest in the sea.
"Trying to study anything that lives in the sea is not easy,'' Ballance says. "And great white sharks are even harder. Places like Stewart Island and the Chathams give you a little glimpse into a small part of their year, their lives.
"New Zealand's great whites are these ocean travellers; they make huge voyages up to the tropics each year.
"In fact, we can't really even call them New Zealand sharks because they are only here for four or five months a year; they spend two months in transit and the rest of the time either in the Pacific or off the Australian coast.
"Until about 10 years ago, we had no idea they did that.''
However, despite now knowing the movement patterns of great whites, the reasons for such migration remains murky.
"Shark scientists will speculate that maybe they are following whales that are heading to tropical waters to calve; or that the tropics see massive spawning of fish species ... we know what they do, but not really why they do it.''
In regards a great white's diet, it isn't fussy. Once it reaches adulthood 10 to 15 years after birth, it will be more than 4m long (some have been measured at more than 6m) and can hunt almost anything in the sea.
Seal pups, other sharks, dolphins, fish, squid, dead or ailing whales . . . the menu is varied. When retired Otago Museum curator John Darby did an autopsy on a large female shark found dead in Otago Harbour in the 1960s, he found a few marine snails, along with an entire crayfish pot, which was bent out of shape.
Humans do, on occasion, find themselves closer to those 24 lower and 26 upper teeth (all serrated, all designed for tearing flesh) than they might prefer.
According to the International Shark Attack File (ISAF), great whites (80), tiger (31) and bull sharks (27) have been implicated in the majority of the 160 "unprovoked'' fatalities around the world since records began in 1852.
(The ISAF only records "unprovoked'' attacks, versus those involving an activity that would typically attract a shark, such as spear fishing and/or having bleeding fish in the water.)
However, the ISAF points out that correctly identifying the type of shark involved in an attack on a human is difficult (for example, victims rarely make adequate observations, and tooth remains are seldom found in wounds). Thus, it urges caution when it lists the "big three'' in regards attacks, adding that there will be a bias towards those species more readily identified.
There were six fatal unprovoked shark attacks in 2015 out of a global population of 7.4 billion people, Ballance notes, adding there have been eight fatal shark attacks in New Zealand since 1852. "In comparison, about 100 people drown in New Zealand waters each year.
"If you ask someone like [her partner] Malcolm, he'd say just don't swim near a seal colony. Dawn and dusk are not great times to be in the water around a seal colony.
"I hope people come away from the book with a sense of great respect for great white sharks, because they are supremely adapted to their environment.
"We are seeing more sharks, but I don't think that's particular to Stewart Island.''
There are a few reasons why: prey populations - including fur seals - have increased since the 1950s, after being decimated by hunting.
"The Great White activity around Stewart Island has only been happening since the seals have started coming back,'' Ballance says. "Also, great white sharks have been protected in New Zealand since 2007. I think that has helped.''
Ballance has a thirst for knowledge that has taken her from the bush of New Zealand to the back and beyond of various corners of the globe.
She has studied tigers, wild horses, spectacled bears, marine iguanas, weta and kakapo (among other species), roaming from the crags of the Southern Alps to the steppes of Mongolia and Russia and the steamy jungles of Ecuador.
In 1990 Ballance moved to Dunedin, where she lived for 18 years, during which time she worked as a researcher then producer at NHNZ, completing a range of documentaries, including To Save the Kakapo, which won a merit award at the Missoula International Wildlife Film Festival, and Power to the Ocean, which won a gold medal at the New York Film Festival.
She has also written more than 25 natural history books, often in collaboration with photographer Rod Morris.
Ballance left the Dunedin-based documentary production company in 2008, heading to Wellington to take up a role as producer for the Radio NZ show Our Changing World.
"I was always interested in nature but I wouldn't say I was particularly obsessed, until I started zoology at the University of Auckland and ended up completing my master's at Massey. The more I studied zoology, the more fascinating it became. I decided that's what I wanted to do.
"People love documentaries and learning about the natural world. Sadly, a lot of people, particularly those in big cities, they don't get the chance to get out and experience nature.
"But people in Dunedin are blessed. You can go out and see albatrosses, sea lions and penguins. That's incredible. I lived on the Otago Peninsula, in Portobello, and never tired of that.''
She still lives close to the sea.
"We look out over Wellington Harbour and can see seabirds. Now and again we have seen big pods of dolphins. I'm still waiting to see orca.''
Among all her travels, Ballance rates New Zealand's subantarctic islands among her favourite wild places.
"A while back I got an incredible opportunity to go to Campbell Island to study feral sheep for a few months. Here's this remote island that's home to albatrosses and penguins. That fed my love of New Zealand islands.
"In my lifetime I have seen a number of these islands become predator-free. It is like stepping back in time. The birdsong is incredible.
"It makes you realise what we have lost on the mainland and what we are trying to get back though initiatives such as Predator Free 2050,'' she says of the Department of Conservation-led initiative to rid New Zealand of three of its most damaging introduced predators; possums, rats and stoats.
"I trap rats in my backyard and try to volunteer on conservation projects when I can. I think it all helps.
"As a whole, New Zealand is lucky. We aren't looking after it as well as we should, but we are lucky.''
Factfile - Alison Ballance
Alison Ballance is a zoologist, diver, wildlife film-maker and radio presenter.
She is an award-winning writer, whose 29 natural history books include Kakapo: Rescued from the brink of extinction, which won the 2011 Royal Society of New Zealand Science Book Prize.
She has also been shortlisted for the New Zealand Post Children’s Book Awards for Hoki: The story of a kakapo, and the New Zealand Book Awards for Southern Alps: History and natural history of New Zealand’s mountain world.
