Marine Biology

Migratory Patterns of the Gray Whale



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Studying the migratory patterns of the Gray Whale (Eschrichtus robustus) is a fascinating journey. The reasoning and nature of the patterns they repeat throughout their life span is as amazing as it is predictable. The Gray Whale is a creature of habit seeking a steady water temperature and feeding ground for the mating season portion of their year.

A little background on the Gray Whale is that it belongs to the phylum Chordata, order Cetacea, Family Eschrichtiidae, and genus Eschrichtus hence it's scientific classification of the above mentioned Eschrichtus robustus. The Gray Whale is the sole meber of it's family and adult males measure 13.7 - 14 meters in length and females are just a tad longer. Each sex can weigh anywhere from 27,200 to 36,300 kilograms. This is one big mammal! While Gray Whales have no dorsal fin they do have a dorsal hump about two thirds of the way down it's body with six to twelve knuckles along the dorsal ridge.

The Gray Whale has two primary populations at this time, one in the Northeast Pacific which is known as American stock, and one in the Northwest Pacific known as Asian stock. Some facts common to each when migrating are that they blow three to five times in fifteen to thirty second time spans before raising their fluke which is another word for tail. When Gray's dive they can stay down for as long as fifteen minutes and travel at a rate of 4.8 to 9.6 kilometers per hour.

As winter approaches they leave their summer homes in the Bering and Chukchi Seas before they freeze over during Artic winter. They make a journey to protected equatorial lagoons with warm temperatures and plenty of food to particpate in the mating ritual. This migration is the longest known of any mammal on the planet at about 8,000 to 11,500 kilometers each way which translates to a 16,000 to 23,000 kilometer round trip!

While migrating they keep a steady pace surfacing every three or four minutes to blow three to five times. They follow the coastlines and often pop their heads straight up out of the water which leads us to believe they are navigating at least in part by remembering land features although some believe this is only a conduit for social interaction. Gray's are the most coastal whale and can commonly be seen within a kilometer of the coast although with the steady increase of boat traffic over the years they are being forced farther out in many areas. It is also worth noting that not all Gray's make this journey but it is not known why. it is suspected however that it may be these Gray's are no longer breeding.

Some of these Gray's have been spotted originating their migratory journey from the North Atlantic and the Arctic Ocean although this is the exception rather than the rule. Once their journey has been completed the mating ritual begins, most commonly in the warm sunny lagoons of Baja California and Mexico although they do have other protected areas as well stretching farther south. This trip takes anywhere from two to three months and the mothers remain in place for another two to three months while their calves build up strength and blubber sufficient enough to make the journey back up north to prepare for the cycle all over again.

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