Thought to be only weeks old, the pygmy blue whale calf spotted with its mother by a wildlife photographer on May 23 is believed to be the smallest ever observed.
The calf was about a third of the size of its mum, about six metres long, whereas the previous smallest calf sighted was about half its mother's size.
This big bundle of joy was spotted in waters off Ningaloo swimming with its — Australian Institute of Marine Science (@aims_gov_au) #PygmyBlueWhale mum during an AIMS research trip. It's thought to be the youngest ever seen in Aussie waters. #CentreforWhaleResearchLearn more: https://t.co/lSfyBJnhrc pic.twitter.com/j9OyvodmNkJuly 4, 2024
Fully grown pygmy blue whales are typically about 21 metres long.
The discovery coincides with the release of the first-ever drone footage of pygmy blue whales' family life by Charles Darwin University on Thursday.
The footage shows adult whales courting and a mother nursing a calf.
Very little is known about the species' reproductive habits, according to Australian Institute of Marine Science researcher Michele Thums.
"No one really knows where pygmy blue whales calve," she said.
"But here in the Indian Ocean, they are thought to breed and calve at the end of their northward migration off Western Australia's coast."
The WA calf was spotted by photographer Tiffany Klein as part of a research project by the institute and the Centre for Whale Research to tag the elusive animals.
Six other pygmy blues were tagged during the trip, which will transmit data on their movements via satellite when they surface to breathe.
Pygmy blue whales are difficult to tag as they move quickly and spend most of their life below the surface.
"They only emerge for a few quick breaths before diving again for 15 to 20 minutes at a time and resurfacing," Dr Thums said.
"It is really wonderful to have tagged six on this trip, providing us with precious data on their movements."
Charles Darwin University's footage was captured as part of an annual monitoring program in the waters of East Timor, known to be a global "hotspot" for whales.
Project lead Dr Karen Edyvane said the waters of East Timor were providing marine biologists with some of the first glimpses into the daily lives of blue whales.
"Since 2014, our program has sighted over 2700 blue whales in Timor-Leste's waters," Dr Edyvane said.
"On a global level, these numbers are truly extraordinary."
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