The big question still is: Why do these mammals embark on these seasonal movements?
Climate changes, water temperature, depth, salinity, topography of the sea floor and the biggest, abundance of food, all plays a major roll in these events.

Although most baleen whales are found in all oceans, they still take on these extensive migrations. These migrations are time-coupled to the breeding/mating season.

Whales travel to cold waters for feeding; they go to warmer waters to give birth. One of the most dramatic whales that visits the Gulf of Maine is the humpback whale, whose Latin name Megaptera novaeangliae means "big-winged New Englander." It is known for its spectacular leaps and long, white side flippers. About 100 humpback whales arrive on Stellwagen Bank, a newly designated marine sanctuary off Massachusetts, in the spring to feed on slender, five-inch-long fish called sand launce.

The Dominican Republic has made these whales' birthing grounds on Silver Banks, just north of that Caribbean country, a marine sanctuary. After giving birth during the winter or early spring, mothers bring their calves to the rich feeding grounds of Stellwagen Bank or other parts of the Gulf of Maine. Like all mammals, the mothers nurse their young. A 10-15 foot baby humpback may nurse as long as a year, adding up to 15 feet in length each month. An adult humpback may grow to be up to 50 feet long.

• Southern right whale migration.
  Winter/Spring: During the winter and spring, they are found in their coastal mating and calving grounds. These lie mainly along the southern coasts of Africa (Hermanus, South Africa is a particularly good place to see them), South America (around Chile & Argentina - Peninsula Valdes is a well-known habitat) and in the Great Australian Bight, as well as along the western coast of New Zealand.

  Summer: Southern right whales migrate to colder food-rich waters near Antarctica for the summer, but to where exactly is not known. Most appear to stay in the mid-Southern Ocean but some do feed at the edge of the pack-ice.

   

• Blue whales:
  Winter: warm, low latitude tropical waters (breed and give birth)
  Summer: cooler, high latitude polar waters (feeding)

  Most blues are migratory and travel thousands of kilometres annually between their winter breeding grounds in warmer, low latitude waters around the tropics, where they mate and give birth, and their summer feeding grounds in the cooler, high latitude waters of either the Arctic and Antarctic, where they feed for 3-4 months on the rich supply of krill and other food which occur in huge numbers in polar waters.

  They then migrate back to the tropics segregated by sex and age, the older and pregnant whales migrating first, with the sexually immature whales bringing up the rear. Generally, the larger, older whales migrate the furthest north.

  During this migration, they eat virtually nothing for at least 4 months and live on body reserves. Females give birth in warm tropical waters because the young only have a thin layer of blubber to keep them warm. Females give birth to a single calf about 7m long and weighing 2.5 tonnes. The calves are suckled for 7 months and follow their mothers on the spring migration towards the polar seas. Once weaned, the calves feed on krill and follow the normal migration cycle.

   

• Grey Whales
  The basic migration pattern follows that of most baleen whales, ie between: winter breeding grounds in low latitude, warm waters and summer feeding areas in higher latitudes, cool waters

  i) Western North Pacific This tiny, remnant population migrates north from winter calving grounds off the Korean Peninsula and Japan, to summer feeding grounds in the northern Okhotsk Sea.

  ii) Eastern North Pacific gray whales make a mammoth 20,000 km (12,400 mile) round trip between their southern breeding grounds off Baja California, Mexico and their northern feeding grounds off Alaska and the Beaufort Sea.

  April - November: Arctic feeding grounds
  [October - February: migrates south]
  December - April: Mexican breeding grounds
  [February - July: migrates north]

  In the early winter, they move south to breed in the warm, shallow lagoons along the Mexican coast. The most popular breeding lagoons are San Ignacio lagoon, Scammon's lagoon, and Magdalena Bay, on the Pacific coast of Baja California, Mexico. Around February, the grays migrate north to feed in Arctic waters (western Beaufort Sea and Bering Sea), northwest of Alaska. A few - mainly younger - whales make a shorter journey north from Mexico, stopping off along the coastline stretching between northern California, Oregon, Washington State, USA, and British Columbia, Canada. Some feeding behaviour has been observed in all parts of the range, and around Vancouver Island, British Columbia, Canada, grays are present year-round.

   

• Humpbacks
  Winter: warm, low latitude tropical waters (breed and give birth)
  Spring/Summer/Autumn: cooler, high latitude polar waters (feed)

  Most humpback whales make mammoth journeys every year between their feeding and breeding sites. Because seasons are reversed either side of the equator, Northern and Southern Hemisphere populations of humpbacks probably never meet; those in the north travel towards their breeding grounds in tropical waters as those in the south are travelling towards the pole to feed, and vice versa.

  Humpbacks are capable of travelling at 5 mph but, during such a long journey, they average only 1 mph, resting and socialising along the way. Not all members of a particular population will travel together however. For example, the humpbacks that pass the eastern shores of Australia, on their way to summer feeding grounds in Antarctica each year, stop off in the warm waters of Hervey Bay. The first to arrive there are groups of older juveniles, followed by mature males and then by mothers and calves.

   

• Northern right whales
  They are not known to travel the huge distances that species such as humpbacks and grays do. Nonetheless, some make annual migrations between winter breeding and calving grounds in warmer southern waters, and summer feeding grounds in cooler waters.

  Winter: Most females give birth in the coastal waters of Southeast USA, off the states of Florida and Georgia. However, males and non-calving females are rarely seen in this area and their whereabouts during the winter is not known.

  Spring: In the spring, aggregations of northern rights can be seen in the Great South Channel, east of Cape Cod, and in Massachusetts Bay as they travel north to their summer grounds.

  Summer/Autumn: During the summer and autumn, both sexes are found in the Bay of Fundy (between Maine in the USA and Nova Scotia in Canada), and in an area on the continental shelf, 50 km south of Nova Scotia. There is also thought to be at least one other summer/autumn habitat somewhere in the North Atlantic.