Records for Soviet catches seem to indicate the female adult size is closer to that of the pygmy blue than B. m. musculus, although the populations of B. m. indica and B. m. brevicauda appear to be discrete, and the breeding seasons differ by almost six months.

[6] Although the designation is widely accepted, because of the relatively healthy stocks of pygmy blues compared to the other subspecies, the Committee on the Status of Endangered Wildlife in Canada has questioned whether the subclassification of the pygmy blue whale has been driven by the interests of the whaling industry.

[13] Aggregations of their preferred krill are also found along the south eastern Australia “Bonney” coast during the late autumn and summer.

[12] This is where The Bonney Upwelling occurs, which results in cold, nutrient-rich waters coming up to the surface from the deep sea and submarine canyons, allowing krill to flourish.

[15] It allows the whale to save energy and maximise horizontal movement by keeping drag at a minimum and staying close to the surface for air supply.

Pygmy blue whales spend over 90% of their time in the top 24m of the water column, and the mean depth is less than 24m for 99% of their migratory dives.

[14] Pygmy blue whale populations can be differentiated acoustically, with each producing calls with slight differences.

[17] There are differences in the three call types regarding frequency content and modulation, as well as the number of units, which suggests how these are from three distinct ‘acoustic populations.'

[19] There are links to climate cycles affecting the behaviour of pygmy blue whales, with there being up to 10 times more directions of songs during La Niña compared to in neutral or El Nino years.

[12] The migratory route of pygmy blue whales goes through locations that come in contact with offshore oil and gas activities, fisheries, and shipping routes, which exposes them to the main threats of vessel collisions, entanglement in fishing gear, noise interferences, and pollution.

[citation needed] A new population of pygmy blue whales was discovered in the Indian Ocean in 2017, with the aid of nuclear bomb detectors.