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Dolphins catch fish using giant shell tools

In Shark Bay, Australia, two groups of dolphins have figured out how to use tools to help them catch fish. They are known as the spongers and the shellers. I introduced you to the spongers in a previous blog so today, let’s meet the shellers.

Shelling is a skillful fishing technique practiced by a culturally distinct group of bottlenose dolphins living in Shark Bay, Australia.

Bottlenose dolphins are well known for having highly developed social skills, and being extremely clever, self-aware, and curious. These qualities make dolphins natural pioneers and innovators which is something we can both relate to and marvel at.

Bottlenose dolphins are gregarious and highly social and in last week's blog, we discovered how they live in fission-fusion societies. This means that they hang out together in small social groups (fusion) but these groups are not set in stone and change over time as dolphins leave (fission) and join again (fusion). Who is with who can change hourly, daily, or remain stable over longer periods. Dolphins, like us, live their lives embedded in a fluid social community with plenty of opportunities to take notice of what other dolphins are doing and learn from others.

A group of bottlenose dolphins at the surface.
Bottlenose dolphins live in diverse and fluid societies.

Tools of the trade

Tool use by dolphins is no mean feat when you bear in mind that they don’t have hands or feet, let alone opposable thumbs!

The spongers pry off a cone-shaped marine sponge growing on the seabed and wear it as a protective glove over their beak. This spongy tool protects their face and mouth from scrape injuries and stings while prodding around on the seabed in search of flatfish. The fish hide in deep-water, rocky channels and are tricky for dolphins to detect using echolocation as they lack swim bladders. Only the spongers can access these extra nutritious fish by physically poking them out of hiding using with their protected beaks.

Dolphin using a sponge as a tool
This dolphin is using a sponge to forage (S. Allen, Shark Bay Dolphin Research)

Shelling point

The shellers use gigantic snail shells that have been abandoned on the seabed as their fishing tool of choice. They target nutritious larger fish that are hard to catch and chase them into their shell trap. The dolphin then wedges their beak into the shell’s opening to prevent the fish from escaping and carries the shell to the surface. They then maneuver the shell above the water – tipping it this way and that to drain out the seawater before then jiggling and shaking the reluctant fish out tail first, straight into their mouth – genius!

A sheller called 'Mash' shaking his fish supper from a shell.
A sheller called 'Mash' shaking his fish supper from a shell. (A. Pierini, Shark Bay Dolphin Research)

Friends learn from friends

Sponging is a skill predominantly learned by dolphins from their mothers during the extensive time they spend together one-on-one in the early years. Shelling is different because most dolphins learn to shell from their friends and so shelling spreads sideways within a generation of dolphins. Both males and females are known to shell and most shellers know one another and spend lots of time together. A dolphin named Osmo learnt to shell recently when Julian, a well-known sheller joined Osmo’s group and demonstrated this specialised fishing technique.

We can only imagine that there are more incredible dolphin tool users out there in as-yet-undiscovered dolphin cultures.  We cannot wait to find out what these groups of dolphins are using to help catch their prey.

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