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Blue Whale Migration

Abhijit Naik
The migration pattern of the blue whales is undoubtedly one of the most intriguing attribute of kingdom Animalia, and that's exactly what we will try to unravel in the following write-up - the journey of blue whales from cold polar waters to warm tropical waters, and back.
The vast natural habitat of a blue whale spans across various oceans of the world - right from cold waters of the polar region to the warm waters of the tropics. Most of the whales which resort to migration, do so for a specific reason.
In case of blue whale, the reason is drastic fall in temperature of polar region which it inhabits in summer.
The freezing temperature of the high latitudes that this species inhabit falls even further and results in formation of ice during the winter season, and that is where migration, which happens to be one of the most amazing blue whale adaptation, comes into play and helps the species survive.

Some Facts about the Blue Whale

The blue whale (Balaenoptera musculus), which boasts of being the largest mammal on the Earth, is also one of the most endangered species on the planet. While the population of this species in Antarctic itself was numbered 200,000 in the past, the same all over the world has been reduced to somewhere around 2000-5000 as of today.
Again this is just an estimated figure, with some sources suggesting that the actual number is less than 2000. And that seems true if you take into consideration the fact that blue whale sightings have become a rare occurrence of late.
As of today, the geographical range of the blue whale species spans across the Antarctic, Arctic, North-east Pacific, North Atlantic and the Indian Ocean.
While the habitat of this species is typically characterized by deep, cold temperate waters, it is known to migrate between polar and tropical waters which happen to be its feeding ground and breeding ground respectively. On an average, these gigantic creatures migrate for thousands of miles to the warm waters of various oceans of the world every year.

Blue Whale Migration

In course of migration, blue whales travel for several weeks and cover thousands of miles in the vast expanse of marine biome. In a broad sense, the blue whale habitat can be divided into summer habitat (or summer feeding grounds) and winter habitat (or winter breeding grounds).
While food is available in the cold high latitude waters in abundance, this region becomes inhospitable during winter, and therefore, the whales are left with no option but to migrate to warm low latitude waters.
This migration pattern that the blue whales follow is guided by ocean temperatures, with a fall by certain degrees prompts the animal move towards warm waters.
With the onset of winter, the journey of a blue whale begins from the cold waters of the Arctic or Antarctic ocean to the warm tropical waters towards the equator. As with most of the marine species, the warm tropical waters act as a breeding ground for the blue whales as well.
Mating rituals begin after they cover thousands of miles and reach the tropical waters. The gestation period for this species ranges between 10-12 months, which implies that, if mating occurs this year, the female will give birth to a single calf when it returns to these tropical waters the next year.
As the calves have a thin layer blubber to protect them from cold, this migration to warm tropical waters turns out to be a boon for their survival.
Blue whale calves are suckled for the next few months, in course of which they stay with their mother. With the onset of summer, blue whales begin their journey back to the cold waters of the high latitudes.
By the time they reach the polar areas, their feeding grounds are abundant with life, which means that there is ample food for these whales to feed on. More importantly, there is no dearth of food for juveniles which begin feeding on krill once they are weaned.
The calves are left to fend for themselves within a year of their birth, and very soon they set out on their first migratory journey, with several to follow.
While the blue whales from Arctic ocean and Antarctic ocean both resort to migration, the fact that seasons are opposite in both the hemispheres ensures that there is no clash in their movement.
While Arctic blue whales migrate to tropical waters somewhere during the middle of the year when it is summer in northern hemisphere, the Antarctic blue whales do so somewhere during the end of the year when it is summer in southern hemisphere.
That the migration pattern in this species is governed by gender and age, with older whales as well as the pregnant whales setting out on the journey to tropical waters first, is one of the most fascinating attribute of migration in this species. More importantly, these whales do not eat anything but rely on their reserves, in course of this migration.
As fascinating as this information may seem, several scientists argue that migration of whales is one of the least known attribute of the marine biome, with several facts about it yet to surface. However, the chances of these facts coming to light are quite dim with changes in ocean temperature continuing to make some serious alterations in their migration pattern, and threatening the very existence of blue whales on this planet.