One Journey Ends: Another Begins
By Tom Lewis
Hello, Journey North readers! I have just returned from my second
trip to San Ignacio Lagoon this year. The year 2000 has been a very interesting year for gray whales. The best
news was the cancellation of the proposed salt works project in Laguna San Ignacio. But the not-so-good news is
the higher than usual number of gray whale deaths along the migration route and dead whales (approximately 30)
stranded inside the lagoon. Looking back on the season, I'm writing to share my year-end thoughts with you.
The Migration Trail: Any Shut-eye Along the Way?
When we arrived in the lagoon at the end of March, not many gray whales were left. Most of the animals had
already begun their long swim north. Almost all the remaining whales were mothers with calves, and a few juvenile
whales were still hanging around. The mothers and their calves were actively swimming up and down the lagoon, strengthening
the calves for the northward migration. The trip takes gray whales 2-3 months to complete. Is there any resting
along the way?
Gray whales do travel 24 hours a day. Scientists have found no real difference in the whales' swimming patterns
during nighttime hours. How do they rest along the way? For many years, scientists were unsure about this question.
They had long observed whales lying motionless on the surface in an activity called "logging." Whales
"log" for short periods of time, 20-30 minutes or so, but no one knew what was actually happening. We
knew they were resting during these periods, but were they sleeping? If they are sleeping, do they sleep like we
We know that whales are voluntary breathers, which means they must actually think each time they take a breath.
Humans don't have to do this, we can basically go unconscious while we sleep. How do whales sleep if they must
remain conscious to breathe? For many years, there was an idea that dolphins are able to shut down one half of
their brain and keep the other half active, allowing them to rest half of the brain at a time. This sounded pretty
far-fetched, and scientists were skeptical about the idea. But several years ago, a Russian scientist put this
idea to the test. He placed electrodes on the heads of bottlenose dolphins and recorded their brain waves over
long periods of time. His results showed that these dolphins actually put one hemisphere of their brain to rest
at a time, while the other half remained active! No one has performed the same experiment with large whales, but
presumably whales may be doing the same thing, allowing them to "sleep" for short periods each day. What
do you think?
Strandings always concern scientists, and strandings along the migration route can occur for a variety of reasons.
When a gray whale washes ashore alive, the cause is almost always due to sickness. Whales, being mammals, suffer
from some of the same diseases as humans. In many cases, the cause of death is pneumonia. However, pneumonia is
a secondary infection, one that is caused by something else. By examining the dead whale's lungs, scientists can
determine whether the whale died as a result of pneumonia, but it is nearly impossible to determine what caused
the pneumonia condition. So, in most cases, scientists are unable to determine the real cause of death for stranded
animals. What are your thoughts?
Is the Food Chain Changing?
The unusually large number of deaths inside the lagoon and along the migration route this year is still a mystery
to scientists. There are some possible explanations, but the exact cause is still unknown. One consideration is
a possible change in the Bering Sea food chain. This is still not well understood, but it could be that gray whales
simply did not get enough to eat last summer in Alaska to sustain them throughout the long migration. Many of the
stranded whales were emaciated (very thin), which could be a result of a lack of food. However, most whales that
strand are emaciated because they have been sick and have not been eating. (When you have the flu, do you feel
Has the Carrying Capacity Been Reached?
Another possibility is that the current gray whale population of about 26,000 whales is as high, or higher,
than it ever has been before. If the population has grown too large, it could have exceeded the carrying capacity
of the environment. In any population of animals, the size of the population is limited by the amount of food the
environment can supply. If the population outgrows the amount of available food, the population will begin to decrease.
If this has happened in the case of gray whales, some of the whales (usually the slower, weaker individuals) will
not be able to get enough food to sustain them through the migration period.
To date, scientists do not understand the meaning of the large number of deaths this year. Gray whales will be
monitored over the next few seasons to see if the problem continues.
There is much that is still unknown about whales. But the more we study them, the more we will learn. Thanks to
fellow scientists and observers like you, we are learning more and more about how these magnificant animals go
about living their lives. Keep up the good work, and I will look forward to filing my reports from San Ignacio
Lagoon again next year.
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