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19.06.12

THE CONSERVATION COLUMN: The Grey Whale Migration

Dr Lei Lani Stelle is an Earthwatch researcher, grey whale expert, and Associate Professor of biology at the University of Redlands in Southern California. Her research assistant, Amanda Atkins, worked with Earthwatch on the Whales of British Columbia project and is pursuing graduate education for marine biology and science writing. In this month’s CONSERVATION COLUMN, they discuss grey whales and human threats to marine mammals…

Of all the fascinating creatures that inhabit the world ocean, perhaps none are as enchanting as whales. These magnificent megafauna have captivated our imaginations for thousands of years, beloved throughout the world for their intelligence and gentle grace. Along the western coast of the United States we are especially fortunate to have several species roaming our waters; from gigantic blue whales and charismatic humpbacks to cunning killer whales. One of the most intriguing of these cetaceans is the eastern Pacific grey whale, a species renowned for its annual migration from northern Alaska to Baja California, Mexico.

Meet the grey whale

Grey whales (Eschrichtius robustus) are called such for the natural pigmentation of their skin: a dark slate colour with mottled grey-and-white patches. They are mysticetes (baleen whales) and reach an average size of 12-16 meters and between 30-40 tons at maturity. Unlike other great whales, which usually possess a prominent dorsal fin along their mid-back, greys are distinguished by their dorsal “knuckles”: a series of small ridges trailing to the flukes. Grey whales feed mainly on amphipods by scooping up sediment from the sea floor and using their baleen as a sieve to filter out and capture prey in a behaviour known as “mucking”.

The grey whales we know today exist in two distinct populations: western Pacific grey whales, found in the waters between Russia and southern Korea and estimated to number no more than 130 individuals; and eastern Pacific grey whales, found along the west coast of North America. Eastern Pacific grey whales appear to have successfully rebounded from years of whaling, currently hovering between 20,000-22,000 individuals, and in 1994 they were removed from the Endangered Species list. These greys undertake one of the longest migrations of any mammal, an annual roundtrip journey of 16,000-20,000 kilometres. In summer months they can be found gorging themselves in the cold, prey-rich waters of the Bering Sea and Gulf of Alaska; in autumn, many greys begin the long trip south along the west coast to the quiet, warm, protected lagoons of San Ignacio in Baja, where they can breed, give birth, and nurse young until they start north again in the spring.

 

Up close and personal

 

Vessel strike and plastic peril

While this annual migration is a delight for whale lovers, providing opportunity for some of the most amazing whale watching encounters in the world, for the whales it is a gauntlet of potential hazards. Because they tend to hug the coast, travelling within 10 kilometres of shore, grey whales frequently come into direct contact with humans, and these interactions can have disastrous consequences. Much of the greys’ migration path is overlapped by shipping lanes and recreational areas, leaving the whales vulnerable to vessel strike. These accidents are usually fatal for the victims: of 23 observed instances of large vessel strike on grey whales between 1975 and 2002, there were 16 recorded whale deaths. Note that these vessel strikes are only the reported incidents - most go unreported. Many more whales become entangled in long line fishing nets and other equipment. The lucky whales are reached by experts and cut free, escaping with minimal injury; others do not survive. Pollution poses another huge issue, because when human trash and debris become embedded in the ocean floor, grey whales can ingest it during feeding. Just this past April, a dead grey whale washed up in Seattle with 20 plastic bags, small towels, surgical gloves, and a golf ball in its stomach.

Keep your distance

A further, more delicate concern is that vessel disturbance - caused by the growing commercial whale watching industry and an increasing number of recreational boaters - can interrupt natural whale behaviour. The U.S. Marine Mammal Protection Act addresses the disturbance problem by prohibiting the harassment of any marine mammals, which includes feeding, pursuing, or chasing them. This act and other international regulations recommend maintaining at least a 100 metre distance from any marine mammal, avoiding head-on approaches, and keeping out of their swim path. These guidelines are reasonable for respecting an animal’s space, but are consistently ignored for one reason or another - a whale watching outfit is vying to please its customers, or a private vessel owner is simply unaware any regulations exist - and are not always strictly enforced.

 

Play time

 

Safeguarding the future of these gentle giants

The key issue of human disturbance is where our research comes in. With the help of Earthwatch volunteers we are monitoring disturbance to grey whales in Southern California through observations of their behaviour and dive physiology. Each individual whale has a steady breathing pattern and natural swimming behaviour that can be significantly altered when under stress. A stressed whale displaying avoidance behaviour might abruptly change swimming direction or speed to evade an approaching boat. If a whale becomes crowded or stressed and has to switch from feeding or resting in order to swim away from a boat, it loses the time it would normally spend in those behaviours and can cost the animal valuable energy. We observe the whales and their behaviours, both on the water and from shore, and compare observations in conditions of high marine traffic and low marine traffic. In addition, we are performing an injury study using the grey whale photo-identification catalogue to quantify types and frequency of injuries—scars, entanglement marks, open wounds from ship strikes, etc. These studies allow us to determine whether the current marine mammal protection and whale watching regulations are working effectively. We have recently expanded these projects to include all California marine mammals, which face many of the same threats as the greys. With enough data, we can advise commercial whale watchers, recreational vessel owners, and fishermen how to adjust their methods in order to improve conditions for marine mammals, ensuring they survive and thrive for generations to enjoy.

In the age of whaling, which decimated whole populations of many species of whales, grey whales were known as “devil fish” for their fiercely aggressive defensive behaviour against hunters. Today they are gentle giants, intentionally approaching humans with warmth and friendly curiosity. It is a complete one-eighty turn in natural behaviour that demonstrates the positive changes that can occur when we pay the ocean and its inhabitants the respect they are due.

For more information on Earthwatch, click here.

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