SpruceRoots Magazine - May 2000

 

The simple fact that grey whales spend the winters feeding and breeding in the warm sunshine and serene lagoons along the coast of Baja California and Mexico should be enough to persuade anyone with lingering doubts that homo sapiens cannot claim the mantle of most intelligent species on earth.

by Ian Lordon

These enormous marine mammals are again brushing near the shores of Haida Gwaii, rewarding sharp-eyed residents with a spout or even a breach, as they stop over briefly on the way to their summer feeding grounds in the northern Pacific Ocean.


The whales are returning from two or three months in the shallow lagoons of Baja California and Mexico where expecting mothers gave birth to calves, and single females were courted by males with procreation in mind.


The gestation period for grey whales lasts at least twelve months, so calves conceived this year will be born when the mother returns next winter. Calves are five metres long at birth and weigh 700 kilograms. Each day a newborn calf will suckle up to 200 litres of milk containing ten times the fat found in cow's milk and put on 35 kilograms. By the time mother and calf are ready for the long journey north, the newborn will have grown by two metres and nearly doubled its weight.
The journey, covering nearly 10,000 kilometres over two or three months, is one of the longest mammalian migration routes in the world. Every spring the whales swim along the coastline of North America all the way to the Bering, Chukchi, and Okhotsk seas between Alaska and Russia.


Grey whales are bottom feeders and eat small crustaceans like amphipods and tube worms found in the sediment on the ocean floor. Instead of teeth, grey whales have baleen, a series of around 150 fringed, overlapping plates between 5 and 25 centimetres long hanging from each side of the upper jaw. The plates are made of a fingernail-like material called keratin that frays out into fine hairs on the ends inside the mouth next to the tongue. To feed, a whale dives to the bottom, rolls on its side, and draws sediment into its mouth. As it closes its mouth, water and sediment get pushed through the plates which traps the food on the inside near the tongue to be swallowed.


The ocean floor of the shallow north Pacific provides a vast and ideal feeding ground for grey whales where they take advantage of the long daylight hours of summer to fatten up for the return voyage south.


Although they can dive 120 metres below the surface, grey whales prefer to avoid deep water for easier feeding. This leads them very close to shore and they've become one of the more renown whale species as they are so often sighted by people in coastal communities.

The grey whale is so named because of the grey patches and white mottling on its dark skin. The skin is usually marred by scratches, scattered patches of white barnacles, and orange whale lice. A full grown female will reach 15 metres in length and weigh 30-35 tonnes. Males are slightly shorter at 14 metres and much lighter at 16 tonnes. Both sexes have a streamlined body with a narrow, tapered head.


The grey whale has no dorsal (top) fin. Two thirds of the way back on its body is a prominent hump followed by a series of six to twelve knuckles along the dorsal ridge extending to the flukes (tail). The flukes are just under four metres across with pointed tips and a deep notch in the centre.


At one time there were three distinct grey whale populations. One in the north Atlantic was hunted to extinction around 1700. A Korean population in the northwest Pacific was hunted until 1968 and today is very rare. And the third, the Californian population, was hunted to the edge of extinction in the 1850's when the calving lagoons were first discovered.


Poor markets for whale products spared the population and allowed it to bounce back somewhat until the early 1900's when factory boats again threatened to wipe out the stock. The grey whale was given partial protection in 1937 and full protection ten years later by the International Whaling Commission. The population has since recovered and now numbers over 20,000, a figure some scientists claim is approaching the original size.


Other than hunters, who nicknamed them 'devilfish' because of their violently defensive behaviour when threatened, the grey whale's only predators are Orcas (killer whales) and large sharks. Orcas are known to bite into the flippers and flukes of large whales and hang on until the whale tires and succumbs to attack. It's not uncommon to spot scars from the teeth of an Orca on the flukes of surviving grey whales.


Just like every other mammal whales need to sleep. But when you breathe air and live underwater this can be a tricky proposition. Whales 'cat nap' between breaths. When the whale feels the urge to breathe, it will wake up and take a breath before returning to sleep. The period between each breath can last from fifteen minutes to several hours depending on the age and species of whale. Because whales often travel in groups called pods, one or more whales will remain awake and alert for signs of danger while the rest sleep.


While awake, greys are one of the most active species of whale, and lucky observers can catch them in the act of spouting, sounding, breaching, and spyhopping.


Spouting is the exhaling of air, water vapor, and water drops which occurs when the whale breathes. It is some times called a blow. Sounding is when the whale shows its flukes and is diving. Breaching occurs when the whale leaps almost clear of the water and falls back with a splash. Spyhopping is the whale pushing its head vertically upward out of the water until it can see above the surface. It will tread water, or stand on its flukes in shallow water, and sometimes rotate slightly. A spyhop can last from 15 to 30 seconds.


Although greys are not notorious singers among whale species (the Humpback whale is probably the most famous for its subsurface serenades), they do sing in a manner of speaking. Grey whale song is characterized by clicking, knocking, and bleating sounds as opposed to the more familiar long winsome notes produced by Humpbacks. Grey whales are not echo-locators like Orcas and dolphins which use sounds to navigate and 'see' underwater, leaving scientists at odds over the significance of grey whale song, its meaning, and its uses. To hear what a grey sounds like underwater, check it out on the web at:

http://www.ocregister,com/science/features/seaview/sea/sounds/gray_whale.av or

http://www.mbari.org/rd/acoustics/

 

SpruceRoots Magazine - May 2000