The Season of the Gray Whale
Topics: Biology, Environment
In late fall, the California gray whales passes south along our shoreline to the warm waters of the Sea of Cortez and the lagoons of Baja California, Mexico. Leaving the rich feeding grounds of the Bering and Chukchi seas off Alaska, these baleen whales travel along the coastal margins traveling a distance of approximately 6000 miles to breed and give birth. This round trip of 10,000 to 14,000 miles is considered among the longest annual migration of any mammal. Frequently these whales can be seen from our shoreline with great viewing site off the Point Reyes National Seashore or off Point Montara to the south. The whale is considered a conservation success story because protections instituted in the early 1930's have allowed populations to rebound from possibly less than 1000 individuals.
Leading my last wildlife trip of the year with SF Bay Whale watching last weekend, we spotted a resident gray whale at the southeast Farallon Island, likely an individual among the two hundred or so considered to be resident. These whales are generally juveniles who do not participate in the migration but feed along the shores of California. As opportunistic feeders, the whales scrape along the bottom filtering out crustaceans with their baleen, or scoops krill from the water or even in kelp beds.
As an undergraduate I studied these whales in Laguna Ojo de Liebre (also known as Scammon’s Lagoon after the infamous whaler of the name) and Guerrero Negro in the Baja Peninsula. Camping along the margins of an estuary, we counted and identified whales, monitored movements and even dived the lagoon to observe behavior and collect bottom samples. At that time it was believed that the whales did not feed during their visit to Baja, or along the way, but relied instead on the fat stored from the rich feeding grounds to the north.
Our observations of feeding whales, the verification of food in the lagoons, and other observations of feeding along the coast helped disprove that theory. Gray whales are opportunists, and this opportunism of feeding, migrations and non-migration may have helped the survival of the species. Back in the day before tighter restrictions were in place in Mexico, we commonly paddled our longboards across the lagoon to the sand dunes separating the calm waters from the sea. Juvenile whales would bump our boards and adults 40 feet long passed a hand's breadth beneath us — with a grapefruit-sized eye staring back at us. Friendly whales frequently rubbed their parasites alongside our inflatable dinghy, as whales spy-hopped, breached and spouted all around us as we collected our data.
I recall surfing the lagoon mouth as whales passed through the narrow channel nearby, and slid on breaking waves from the shallow sand into the deeper channel, gliding over the whales' backs. Large tuna and sharks also shared the waters and it was not unusual to see a beached baby whale with the large serrated gnaw marks of white sharks.
Diving in the lagoon to collect bottom samples, whales would appear and disappear like grey ghosts or slide along creating a muck cloud. In addition to feeding on planktonic shrimp, gray whales bottom feed, skidding along the soft sediment, collecting mouthfuls of muck and loads of crabs, shrimps, isopods and other crustaceans and invertebrates.
Like people, these whales are right or left sided, and older whales actually become blind in one eye from the continued contact with sediments.
At the time around the American Civil War, the gray whale population was dramatically reduced by hunting in the lagoons. Especially vulnerable because of their coastal navigation, and exposure in what became called the “whaling lagoons,” the eastern Pacific gray whale population dwindled. Over 150 years ago, whalers like Charles Scammon slaughtered whales with abandon like fish in a barrel until the lagoons were described as vacant. Today, whale watch tours take tourists onto the Mexican lagoons to watch hundreds of these gentle whales. The old pier on Guererro Negro Lagoon still serves as a prime viewing ground.
From Mexico to Canada, whalers hunted the California gray. In fact, a whaling station operated in the San Francisco Bay near Point Molate in Richmond to hunt and process gray whales.
A sister population in the North Atlantic was pushed to extinction and a remnant population of a few hundred individuals lives further west in the Sea of Okhotsk and near Korea. After less than 75 years of systematic whaling the Eastern Pacific gray whale population had been reduced to numbers endangering their survival as a species. The gray whale was given partial protection in 1937 and full protection in 1947 by the International Whaling Commission (IWC).
Today, the gray whale is a conservation success story.
Once estimated at less than 1000 individuals, the population of gray whales is currently between 20,000 and 22,000. Historically, this population is estimated to have been far greater. In 2007, S. Elizabeth Alter and Dr. Steven Palumbi of Stanford University used a genetic approach to estimate pre-whaling abundance based on samples from 42 California gray whales. The researchers reported DNA variability consistent with a population size of 76,000–118,000 individuals, three to five times larger than the average census size as measured through 2007.
The ocean ecosystem has very likely changed since the pre-whaling era including direct impacts from fishing the ocean and other indirect impacts making a return to pre-whaling numbers infeasible. Not all gray whales migrate. A population of about 200 resident gray whales stay along the eastern Pacific coast from Canada to California throughout the summer, avoiding the farther trip to Alaska waters. One of these resident whales has been regularly seen off Southeast Farallon Island in the past year.
New research has questioned past paradigms regarding gray whale migratory and feeding behaviors.
A study recently published by Dr. David Lindberg, a UC Berkeley professor of integrative biology with his former student Nicholas D. Pyenson, suggests that the whales appear to have more evolutionary plasticity than previously imagined. Gray whales survived many cycles of global cooling and warming over the past few million years, likely by exploiting a more varied diet than they do today, according to the paleontologists.
In fact, it appears that gray whales may be highly resilient to environmental changes.
The oldest gray whale fossils date back 2.5 million years, and since then, the Earth has gone through more than 40 major cycles of warming and cooling.
The scientists propose that gray whales survived the disappearance of their primary feeding ground by employing generalist filter-feeding modes, similar to the resident gray whales found between northern Washington State and Vancouver Island. These whales filter feed for krill and other crustaceans similar to other baleen whales like humpbacks.
The new assessment is hopeful for the gray whales survival, and may help them survive the potential impacts of climate change over the next few centuries where an expected sea level rise of several meters, and where alterations in current patterns and temperatures are predicted. Let's hope that increased protections for these and other whales that visit our sanctuary waters, and protecting whale food like krill from commercial harvest, will help these magnificent marine mammals continue to survive the environmental change in the coming century.Tags: Gulf of the Farallones, whales