Blue Whale  |  

Both the Antarctic blue whale and pygmy blue whale have common phenotypic traits such as grey skin with mottled patterns, which enables identification of individuals. When submerged, the blue whale appears to be a luminous pale blue or aqua. They have a pronounced ‘splashguard’ in front of their blowholes, with a single pronounced longitudinal ridge leading forward on the rostrum. Their blow is tall and powerful (approximately 10 m). They have a long, smooth back with a small, variably-shaped dorsal fin set towards the tail. Differences between the two subspecies were first determined by whaling catches in the austral summer feeding season. Differences between the pygmy blue whale and the Antarctic blue whale include: Morphology: the Antarctic blue whale is the largest of the two subspecies growing to maximum lengths of over 30 m; in comparison, the pygmy blue whale is recorded growing to 24.1 m. Despite this difference, determining subspecies in the field can be difficult. Vocalisations/acoustic calls: both subspecies produce distinctive acoustic calls that can be used to identify each species as well as provide insight into geographic and seasonal distributions. Genetics: both subspecies are genetically distinct, however diagnostic genetic markers are not available. The Antarctic and pygmy blue whale have been known to hybridise. Austral summer distribution: the pygmy blue whale is typically found in more northern areas (north of 54° S) at lower latitudes, throughout the Indian Ocean, whereas the Antarctic blue whale is usually found further south of Australia (60° S), circumpolar wide. Blue whale and fin whale hybrids has been documented in five cases. The hybrids – three females and two males – were taken in commercial whaling operations in the Northern Hemisphere.