WHALES
Whale movement and behavior
(Southern Hemisphere Humpback Whale ecology)
Humpback whales (Megaptera novaeangliae) are a cosmopolitan and typically highly
migratory species. In the Southern Hemisphere, they generally aggregate into broad areas within a heterogeneous high latitude Antarctic Ocean environment to feed during summer months, and in the tropical or subtropical coastal waters of continents or island archipelagos during winter and spring for breeding purposes. Evidence for these migrations arises from seasonal variations in whaling catches and survey estimated abundances at different latitudes, observations of the Antarctic skin diatom, Benettella ceticola, on animals in low latitude waters, tag and natural mark returns and satellite tagging results.
There are currently seven (A-G) breeding stocks of the species recognised by the International Whaling Commission – IWC. They are classified according to their winter distributions in coastal waters as: (A) east coast of South America; (B) west coast of Africa; (C) east coast of Africa and western Indian Ocean (including Madagascar); (D) west coast of Australia; (E) east coast of Australia and western Pacific Ocean; (F) south central Pacific Ocean; and (G) west coast of South America. These different stocks/areas are all within one of the six (I-VI) management areas for baleen whales determined by IWC in the Southern Hemisphere (please see figure below).
All the seven breeding stocks were harvested by whaling activities. Some 215 900 humpback whales were caught across the Southern Hemisphere by modern whaling operations between 1904 and 1973, which means a great major part of their populations
feeding grounds
Understanding the movement and distribution of humpback whales in their feeding grounds is difficult due to the remoteness and the size of the Southern Ocean area. A number of dedicated research cruises to improve our knowledge in this area have been undertaken during the post whaling era (e.g. by the Australian Antarctic Division or the IWC International Decade of Cetacean Research / Southern Ocean Whale Ecosystem Research programmes).
Breeding grounds and migratory corridors
The populations C1, D, E1 and G are subject to a detailed assessment and analyses in their breeding areas and migratory corridor in this project. Available data for the assessment includes dedicated cruise data, dedicated land based surveys, satellite tracking and citizen science data as well as historical catch data. The data is being analysed for time of arrival, age classes, habitat preferences, distribution, behavior, identification of resting, breeding and socialising areas as well as temporal and spatial variation of equatorial or near equatorial movement.
Estimated number of humpback whales for the southern hemisphere populations
* Numbers are an estimation for 2020 based on projections and display of populations has been simplified.
Areas subject to detailed studies as part of the Whales and Climate project are:
- Southern Ecuador and Panama;
- The Southern Benguela System of the west coast of South Africa;
- Western Indian Ocean and Southern African regions including the coastal waters of Mozambique;
- Australia East coast and Tasmania;
- Australian West Coast
The main research objectives in this theme include:
- Determining historical and current humpback whale distribution;
- Understanding and determining the main variables driving possible changes in the species distribution between these two periods; and
- Evaluating the climatic, oceanographic and biogeochemical processes influencing feeding, breeding and migration distributions.
