A pygmy blue whale calf has been spotted off Western Australia's rugged south coast in a rare discovery.
While it is not unusual to see the endangered species in southern waters at this time of year, it is far less common to see a young calf, which scientists said would have been born in the area.
The vision was captured near Cheynes Beach, a popular whale-watching spot about 400 kilometres south-east of Perth.
Marine biologist Pia Markovich, who studies blue whales, said there had only been about three well-documented sightings of blue whales with a calf along the southern coastline in the past decade.
"We do see blue whales coming up this time of year, travelling along that coastline heading north," she said.
"But with a calf is pretty unusual, just because it's out of their birthing season."
The pygmy blue whale is a sub-species of the Antarctic blue whale, and slightly smaller.
Scientists want to understand more about the species, which travels north during the Australian winter to feed and give birth in the warmer water.
Difficult to track
Ms Markovich said the population of blue whales was increasing but it was always good to see calves, especially because it was an endangered species.
"When we see little calves like this, they could potentially live to 80 to 100 years," she said.
"Unfortunately, out of the birthing season, we don't know how successful it might be, it might not survive the migration all the way north.
"But we'll keep our fingers crossed."
While blue whales are the largest animals on the planet, experts say they are hard to find and track.
Ms Markovich said because of this, very little was known about the species.
There are believed to be just 1,500 blue whales populating waters around Australia.
Threats to the species include ship strikes, fishing gear entanglement, and chemical and noise pollution.
Ms Markovic said noise pollution was of particular interest, and scientists did not completely understand how it impacted the whales.
"Low frequency noises from boats can actually mask the call of the blue whale," she said.
"If a mum and a calf are swimming together and they are separated, and there's some vessel noise in the area, they might not be able to hear each other.
"You can imagine how big and dark the ocean is.
"They might not actually be able to find each other again."
Once-in-a-lifetime sighting
Jo Barden, who shot the footage of the whales, said sighting the calf was a special moment.
"We'd been looking for whales every day at Cheynes Beach for about a week before and after work," she said.
"We knew it was a blue whale when we launched the drone, we had seen a few but none had come so close to land.
"Definitely a once in a lifetime experience, especially when you see such a young calf."
