The amazing bottlenose dolphins of Shark Bay

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.

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The dolphins of Shark Bay article spread

 

 

 

Tool-use has not spread throughout the bottlenose dolphin population of Shark Bay. Instead, it is passed down certain matrilines, from mother to daughter to granddaughter. As Janet puts it: “Once you’re a sponger, you’re a sponger for life.”
 
We spent hours watching Bitfluke hunt, and Janet explained that spongers spend longer foraging than the other dolphins. I asked if she thought this behaviour was an evolutionary ‘dead end’. “Spongers are loners,” she replied. “They don’t have time to socialise, so I guess that there is a cost. But it works, so they keep doing it.”
 
Smash and grab tactics
 
There are so many remarkable female dolphins in the Bay. Sequel, or Shagrobber as she’s affectionately known, rushes up to pied cormorants and knocks them clean out of the water so that they panic and drop their fish. Then there is Wedges, who specialises in catching huge, 1m-long golden trevally.
 
Back at Peron Point, on our last day of filming, it’s all about aquaplaning. The Peronette calves are flipping and darting in the surf, trying to emulate their mothers. Suddenly one of them, known as Jamaica, gets up to have a go. “That’s a first,” Janet says excitedly. “I’ve never seen such a young calf aquaplaning. She’s only two-and-a-half years old.” A new generation of females are already honing their skills.
 
But what about the males, Ben asks. “Are they really less creative?” Janet hesitates. “I want to say yes, but no: they’re political animals, worthy of Machiavelli. They use their brains in a different way – but that’s another story.”
 
 
How a baby dolphin learns to recognise its mother’s whistle:

 

  • One of the greatest dangers to a newborn dolphin is getting lost or becoming stranded. So, in late pregnancy, the mother starts whistling her unique signature call to her unborn calf. This sound enables the youngster to identify its mother and stay near her.
     
  • A baby dolphin is extremely sensitive to movement, however, and curious young females will often try to kidnap it by racing past so that the calf instinctively follows. The mother then has to steal her calf back. It’s one of the few times that female dolphins show aggression towards each other.

  • When the calf is a few months old, it begins to wander off on short forays. It takes a year to develop its own call sign – an important part of growing up in dolphin society.
 
Tricks of the trade: Shark Bay’s female dolphins have four extraordinary hunting strategies.
 
  • Aquaplaning
    A dolphin rapidly accelerates towards the shore, flattening its body to maximise its surface area so that it can hydroplane onto the beach to catch its prey.
     
  • Grubbing
    In seagrass beds, a dolphin rummages among the plants to root out skulking prey, including snake eels and cuttlefish.
     
  • Giant fish hunting
    This strategy is used by a single dolphin called Wedges, who has learned how to catch huge golden trevallies. It is thought that she snaps her victims’ heads against the seafloor. Wedges takes up to an hour to break up her prizes. Other dolphins come to watch, but never attempt to steal the fish.
     
  • Sponging
    The first known example of tool-use in cetaceans. A dolphin pulls up a basket sponge from the seabed and holds it clamped onto the end of its beak to flush out bottom-dwelling fish.

 

To find out more about the Shark Bay World Heritage Area, click here

To find out more about bottlenose dolphins, click here

 

 

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