The orcas of Bremer Bay

23 September, 2019   By: Vanessa Pogorelic

There's no doubt the great white shark has earned a reputation as the ocean’s most feared killing machine.

This efficient and powerful apex predator faces few threats from other marine animals - expect one.

When faced with a pod of orcas on the hunt, any great white shark, no matter how large or powerful, is doomed.

In the world of apex predators none come close to orcas, also known as killer whales. They’re strong, fast, highly intelligent and love to dine out on a bit of fresh shark – including great whites.

And their numbers off the WA coast are growing.

Looking for clues

Curtin University research scientist, Rebecca Wellard, has been tracking the orca population off the coast of Bremer Bay for the past six years.

Wellard says the Bremer area is attracting the largest number of orcas in Australia but at this time it’s not well known why.

“Over the past 10 years their numbers have really started to increase. But we don’t know why they go there. We don’t know where they come from or why they stay there. They go to this area offshore where there’s a complex underwater canyon group.”

The area, known as the Bremer sub-basin, is about 50km off the coast of Bremer Bay. Wellard says the water there is nutrient rich which attracts a great variety of marine life and presents a smorgasbord of ocean treats for the orcas to feed on.

And finding out exactly what they do like to eat is another orca  mystery that Wellard’s Project Orca research team has been tasked with.

Because not all orcas have a taste for shark.

“They have certain marine life that they like to prey on, so some populations of orcas' will only feed on one type of fish. Some will only feed on seals, some will only feed on sharks.

“We need to learn more about what they feed on down there.”

Killer culture

This highly intelligent marine mammal is actually a dolphin not a whale – the world’s largest dolphin in fact. And as with other dolphin species, orcas exhibit many complex social behaviours.

What makes them highly efficient hunters is their ability to organise and hunt their prey in groups, so they’re able to outmanoeuvre their target. They can even take out a blue whale - the largest animal on the planet.

They also have fascinating social lives.

“Orcas  are really interesting in that they have a culture,” Wellard says.

One of the characteristics of their culture, apart from being fussy eaters, is that the sounds they make have specific dialects or accents. Bremer's orcas, according to Wellard, have a distinctly Australian accent.

“They have a unique dialect compared to other dialects and vocalisations around the world. Their accents are most similar to orcas in Antarctica, but that doesn’t necessarily mean that they go to Antarctica.”

Wellard says different populations of orcas around the world have been found to have very different accents.

Mummies' boys

Another of the orca's cultural characteristics is that they have a matriarchal society.

“Females rule the roost,” Wellard says.

“It’s grandma that rules the pod and they generally stay with their family for their whole lives. Then they’ll split off into new groups within that family.

“But it’s always the females that lead the pod. Other dolphin species will stay with their mum until they’re about three years old then head off on their own. But orcas are really interesting in that the family groups will stay together.”

The bond between family members and the reliance on females is so strong that male offspring will die younger without their matriarchal leader.

“If a mother dies, the sons who live with the mother will have a reduced life span, so they really are mothers' boys. They swim with their mother and the mother helps to feed them and keep that family group together - the family really does rely on its mother.”

This complex social behaviour is the product of a very complex brain, Wellard says.

“They are incredibly intelligent. They have different parts of their brain related to their emotions – they have areas of their brain that we don’t even have or understand. Scientists have done brain scans and there’s a specific part of their frontal lobe that relates to emotional intelligence.”

It is an area of the brain that humans have never developed.

“There are a lot of things that we still have to learn about them.”

Getting up close

It was 2015 when the first charter boats started taking passengers out to view the orcas off Bremer Bay.

There are now two companies that do tours off Bremer. Ningaloo Reef is also a hot spot for orca sightings and while there are no dedicated orca tours off Ningaloo, they can often be seen on whale shark tours around June to August.

Wellard says their behaviour around the boats can be interesting.

“They can be really inquisitive, really friendly around the boats, they can eyeball you.

“On one of my first encounters with them about seven years ago, one of the females came straight over to the boat put her belly up and just eyeballed us, and I was thinking ‘wow, how’s that for an introduction’. She played with us the whole day.”

Wellard says it’s remarkable how little we know about this incredible apex predator of the ocean.

“We’ve only really discovered them in the past 10 years [off Bremer Bay]. They’ve had sightings of them in the Bremer area for decades. But over the past 10 years their numbers have really started to increase. A lot of people don’t even know that we have orcas here in our backyard.

“We have so much more to learn about them. The more that’s known about them the more we can protect them.”

To find out more about Project Orca and the orcas of Bremer Bay, visit projectorcawordpress.wordpress.com

Images: Rebecca Wellard, Project ORCA