Dwarf Minke Whale Biology

DISTRIBUTION

General

Dwarf minke whales were originally described from South Africa, where they have been recorded in the Atlantic Ocean and in the Indian Ocean, at least as far north as Durban]. They have also been recorded off Mozambique (about 23°S). They occur in both coastal and offshore waters along the west coast of Australia from south of Perth to the northwest shelf. Strandings or sightings occur in South Australia, Victoria, New South Wales, Queensland (north at least to Lizard Island), New Caledonia, both North and South Islands of New Zealand, and along the eastern coast of South America from northern Brazil (about 10°S) to Argentina. These records cover most of the year (March to December).

Dwarf minke whales have also been recorded in the sub-Antarctic at about latitudes 55-60°S, with one record as far as 65°S. These records were from December to March. There have been a few unconfirmed records of dwarf minke whales among the ice in Antarctic waters south of South America in the winter months.

Great Barrier Reef

Based on sighting records from dive charter vessels and our observations on Undersea Explorer, dwarf minke whales are found between March and October, but with the majority (about 80%) of sightings in June and July. Most of the sightings are on or to the west of the Ribbon Reefs between Port Douglas and Lizard Island. These sightings at least partly reflect where the dive vessels go, but there are consistent sites such as Ribbon Reef 3 and off the southern end of Ribbon Reef 10. With the help of the dive industry, we have built up a general picture of dwarf minke whale distribution on the northern Great Barrier Reef. We now need more information on what individual whales or groups of whales are doing. To get this information, we have been concentrating our effort in a few areas where whales have been seen consistently, thus increasing our chances of re-sighting individually recognised whales.

Sightings in the northern GBR are most often of single animals or a pair of animals. There are differences, however, in the size of groups seen when moored at a reef and whilst drifting in open water to the west of the reefs. Groups in open water are significantly larger (up to 25 animals during a single encounter, with up to 10-12 animals at the same time). There may be an aggregation effect in open water; we have seen additional whales joining an encounter in progress while the original whales still stayed with the vessel.

Based on records off South Africa and South America, it has been suggested that dwarf minke whales occur closer inshore than the Antarctic minke whales. Although we now have several hundred records of dwarf minke whales on the northern Great Barrier Reef, we know of only one confirmed sighting of the Antarctic minke whale anywhere on the GBR, which we saw briefly and documented on video during our 2000 field season.

Sighting surveys off Western Australia show that dwarf minke whales can be found well offshore (to at least 800km) and overlap in distribution with the ordinary southern hemisphere minke whales in those offshore waters.

Below: Map showing distribution of dwarf minke whales, based on reports in the literature. The sightings in the sub-Antarctic (dark bar) have been mainly south of Australia and New Zealand, probably because this is where most sighting and hunting effort has been concentrated in recent years. The dwarf minke whale almost certainly occurs in sub-Antarctic waters to the south of South Africa and South America.