Animal globetrotters III

Spectacular mammal journeys

Even though there are less long distance travellers among mammals and reptiles than among birds, insects and fishes, the fantastic journeys they make are certainly worth exploring.

From little lemmings to mighty whales, a wide range of different mammals undertake spectacular long distance journeys by land or sea, every year. Of all these journeys, the most incredible voyages are accomplished by certain species of aquatic marine mammals, particularly members of the whale order. So, let's check out some of these incredible mammal migrations today...

Research into mammal migration has revealed that the grey whale undertakes the longest confirmed journey which can average a distance of 10,000-14,000 mile round trip.

It travels from its summer feeding grounds in the Arctic, in the waters of the Bering Sea between Alaska and Siberia, to its winter breeding grounds located off Baja California in northern Mexico.

What's incredible is that the grey whale swims this great distance in a speedy 90 days, twice a year during its migratory cycle. The Blue whale too migrates. It spends its winter in temperate and sub-tropical regions. When spring and summer arrives, it swims to the polar regions to feed in the waters of melting ice caps.

Humpback whales are another species that migrate, but they do so on defined migratory routes. Whether from the northern or southern hemisphere, humpback whales follow the same annual migration pattern every year.

They move from the krill-rich waters of the poles, to the warm waters of the equator, to give birth. Research has revealed that humpbacks travel from the Caribbean to Greenland and Iceland, from Hawaii to Alaska, and from the Atlantic Ocean to Colombia in South America. Dolphins and porpoises too migrate. However, their migratory routes are not as well defined as that of whales.

On land, there are many species of mammals that are long distance travellers. Mass migrations are rather common among certain species, even though the numbers have reduced drastically due to hunting.

The Alaskan fur seal lives in colonies in their breeding grounds in the north. The females travel south each winter to feed in Southern California. While the males remain in the northern waters by the Aleutian Islands, the females journey some 5,000 km southwards each year during September and October.

During the spring however, they return to their colder breeding grounds in the Commander and Pribilof Islands in the Bering Sea and Japan's Sakhalin Island.

Several species of hoofed mammals such as springboks, gnus and American bison too migrate in large numbers. The blue gnus or wildebeests overcome many obstacles on their mass migrations, sometimes even crossing large rivers.

Another famous mammal species that emigrates in large numbers are the lemmings. This small herbivorous mammal has a formidable reproduction rate - more than 100 offspring can be born to a single pair within six months! And so, you can imagine then how fast their population grows. This naturally leads to a scarcity of food within a given area of the Scandinavian tundra and the scrub that comprises their normal habitat.

And when the population size reaches 40-100 individuals per acre, which tends to happen every three to five years, the lemmings emigrate in search of food. However, during this mass emigration, many lemmings die.

Many suffer from the effects of acute overcrowding and disorganisation. They become exhausted and behave in a frenzied manner; they drown in rivers and even fall down cliffs.

In early days, researchers were of the view that the lemmings were committing suicide, but today, it is believed that such action is due to their inability to change course in time. Researchers are also of the view that the eating of toxic plants due to the scarcity of food maybe causing the lemmings to behave in a frenzied manner.

The only mammal equipped with the power of true flights, bats, also travel considerable distances in their migratory journeys, like their counterparts in the avian world. Some exhibit true migration, that is they fly from their summer breeding grounds to their wintering grounds, and six months later, do a turn around to return to their home, to breed again.

Australia's grey-headed fruit bats are known to travel more than 1,600 km (1,000 miles) between October and December from Queensland to Victoria. Even the American red bat migrates from Canada and northern United States to the southernmost regions of the United States and even upto Bermuda, which covers a distance of about 900 km. They often make these long-distance journeys in single-gender flocks. Adult females each carry upto three infants during their mass migrations.

Now don't you think that the long distance journeys these animals make are fantastic, simply because they do so using their own energy and inert knowledge; they don't have powered vehicles, maps and other guiding information to undertake these long journeys. Majority of these animals migrate for food and breeding purposes.

A change in temperature, drought and shortage of food generally determines an initiation of immigration. As they rely on the climate and cues from the environment to make successful journeys, climatic changes and destruction of natural habitats have a drastic impact on animal migration.

This is something we should always keep in mind when we destroy vast expanses of forest land and change the landscape in animal migratory routes. As we explained, earlier, there are many more species of animals that migrate in the animal kingdom. Next week too, we'll bring you some interesting facts about such migrations.