On the west coast of Australia, a population of bottlenose dolphins stunned the scientific world by learning how to use tools. But only females can do it. Nick Stringer finds out why.
It’s 6.30am and the first rays of sunlight glint on the surf at Peron Point, a remote peninsula in Shark Bay at the western tip of Australia. Dolphin biologist Janet Mann is already at her lookout. Below her, 2km of deserted beach sweeps in an arc to Skipjack Point. She radios her research student, Eric, to say that she’s in position. “Copy that,” he replies. “It’s a beautiful day.”
Aussie cameraman Ben Cunningham and I pick our way down the crumbling red cliffs to the shore. We’ve been following Janet and the bottlenose dolphins of Shark Bay for nearly a year. It’s our first day at Peron and we’ve come to film a special group of dolphins known for the death-defying way in which they catch fish.
Still bleary-eyed, I’m expecting a long shoot – possibly many weeks. The action could take place anywhere along a 16km stretch of coastline.
Before Ben can sort out his gear, Eric screams down the radio: “Hydroplaning right beneath me.” A huge adrenalin rush jolts us into action. We sprint the length of the beach to Skipjack Point, where I spot a plume of water ripping along the shoreline. As I catch my breath, I throw the tripod onto the sand and Ben starts filming.
Before us, a spectacular scene unfolds. A dolphin turns sharply and accelerates to over 30kmph, edging closer to the shore, while a large mullet races just ahead of it, rapidly running out of options. The dolphin is now hydroplaning in a few centimetres of water.
The mullet makes one last, desperate flying leap and strands itself on the beach. Its pursuer bursts from the surf to snatch the fish. Completely beached, the dolphin then shuffles back into the water, defiantly tossing its half-dead prey high into the air.
“It’s Reggae!” Janet’s voice crackles on the radio. Later, I learn that Reggae is the queen of the aquaplane – she’s been doing it for more than 20 years.
Meet the peronettes
There are just a few places in the world where dolphins chase their prey onto the beach. In South Carolina, they herd fish onto mudflats – a behaviour filmed for BBC’s Life
series, and described in the November 2009
issue of BBC Wildlife
– but Peron is the only location where they hydroplane and launch their entire bodies onto the sand.
Reggae is joined by Rhythm and Blues. Janet, who is now by our side, says that she has only seen this behaviour in females. “We call them the Peronettes,” she smiles.
For the next 10 minutes, we are treated to an audacious display of speed and acrobatics. As the chase fizzles out, Janet is already halfway back up the beach, snapping pictures of the Peronettes’ calves. It’s a rare opportunity for her to sex them and get a photo id of their dorsal fins.
“There’s a lot of pressure on dolphin mothers: they have just one calf at a time, and may suckle it for up to nine years,” Janet tells us. “While they’re nursing, they have to eat 50 per cent more than the males, so they put their big brains to good use.” With a wry smile, she adds: “In fact, the girls are far more creative than the boys!”
Ben raises an eyebrow quizzically, but we can see Janet’s point – the resourceful dolphin mothers have learned to exploit almost every niche in Shark Bay.
Covering an area of 10,000 sq km, Shark Bay is one of the most diverse and pristine shallow-water bays on the planet. Seagrass beds stretch as far as the eye can see, cut through by deep blue channels, bathing the coastal sand flats and mangroves in brilliant shades of turquoise and indigo. Protected from the open ocean, these sheltered waters make a perfect nursery for the dolphins. More than 3,000 individuals live here.
Back in 1988, when Janet initially drove down a dusty old track to Monkey Mia in Shark Bay, the first dolphin she met was a female that the locals called Puck. Since then, she has shared this dolphin’s life, experiencing the joy and despair of all the calves reared and lost; once, Janet even saved Puck from drowning in a fishing net.
Over the course of 23 years, Janet has tracked more than 1,500 dolphins, and she’s still observing 600 of them today. Much of what we know about wild bottlenose dolphins, especially mothers and calves, comes from her studies.
A star subject
Puck is now 33 years old, and one of the older dolphins in the Bay. She could be the first bottlenose ever to have been closely observed from youth to old age, and is the star of the Natural World film we’re here to make for the BBC.
Last December, we were lucky enough to document the first few hours and days in the life of what will probably be Puck’s last calf, Samu. It was a rare insight that brought home the challenges that these mothers face. When an air-breathing mammal gives birth at sea, its offspring is extremely vulnerable: there’s nowhere to hide and sharks can strike at any time.
After three weeks waiting to film Puck give birth, I had been about to give up, but Janet reminded me that the dolphin had been waiting 12 months. Then, one day, I saw a tiny fidgety splash next to her. A male calf had been born in the night. His fins were still floppy and he had white foetal lines on his flanks. We called him Samu.
Swimming like a wind-up toy, Samu quickly surfaced for air, chin-slapping the water in a very un-dolphin-like manner. Puck stayed by his side, shadowing him everywhere, steering him away from the shore and other dangers. Unable to hunt, some mothers starve for days while shepherding their calves until they become confident swimmers, but Samu learned quickly and he had a big family close by.
Sponging for a living
When Samu was a week old, we took our boat into a deep channel, just beyond the seagrass beds. Eric raised his binoculars and pointed out a dolphin that I hadn’t seen before: Bitfluke. She had a jagged tiger shark bite in her dorsal fin, but that wasn’t the most striking thing about her appearance. There was a big yellow basket sponge stuck on the end of her beak.
Eric’s hunch is that Bitfluke and the other dolphins in her group use the sponges to stir up bottom-dwelling fish. There are lots of venomous species here, including stonefish and stingrays, so the sponges could also offer protection.
Frustratingly, the water is too murky to see anything, but Eric hopes to capture images of the dolphins ‘sponging’ by setting up remote cameras on the seabed. If he succeeds, it’ll be the first footage of cetacean tool-use in the oceans.