Every winter, a parade of gray whales voyages from their Arctic summer grounds to their winter homes in Baja California. The gray and white, barnacle-covered animals will travel a total distance of 10,000 miles or more.
Throughout January, Wayne Perryman and his team will be watching from a converted concessions truck parked at Granite Canyon, near Carmel. Perryman, a scientist at the Southwest Fisheries Science Center (SWFSC) in La Jolla, plans to monitor the whales as they migrate south. Every day, rain or shine, a pair of observers will count passing whales (and fend off the occasional passerby looking to buy a snack).
The last gray whale census, conducted in 2001, showed that the Eastern Pacific gray whale population appeared to be declining. As many as 27,000 whales went by in 1998, but by 2001, the numbers plummeted to 16,000. Perryman suspects that this drop was due to short-term changes in climate, which affected the whales’ access to food.
“Now I think we’re back to normal again, so I’m hopeful that we’ll have a reasonable year,” Perryman said. He guesses that the current whale population is around 20,000.
This year a new whale census technique will debut. Instead of recording whale sightings with paper and pencil, Perryman’s team will use a computer program to track the migrating mammals. When a whale is spotted, the program calculates where it might appear next. Then, when the whale spouts again, watchers can more accurately gauge whether it is the same whale or a new sighting. Perryman said he hopes the new technique will yield better results.
In the past, the National Marine Mammal Laboratory in Seattle conducted the whale counts. The SWFSC group is taking over because California is more convenient for whale watching. This year, both teams will monitor the migration to make sure they come up with similar numbers.
During the warmer months, the Arctic is the place to be. All summer, the whales, which can measure up to 45 feet long, engorge on sea creatures just a few inches in size. Instead of teeth, gray whales have a stiff, bristly material ” like a giant toothbrush ” called baleen. As bottom feeders, the whales eat by sucking in a great mouthful of the sea floor, only a small portion of which is actual food. They then close their mouths, pushing the muddy, watery excess out through the baleen filter. Small animals such as starfish and clams are thus trapped and swallowed.
By late autumn, an alarm sounds for pregnant gray whales, whose instinctual response is to start the journey south from the coastal waters of Alaska to Mexico’s calm lagoons.
Males and other females soon follow. They will all go without food for the next several months, both during the migration and at their winter grounds. Calves are born during the trip or soon thereafter.
Despite years observing the migration, scientists still isn’t clear why whales migrate in the first place. “Nobody knows,” said Perryman, adding that there is a lot of speculation.
One popular theory is that the grays migrate to avoid predation by killer whales. Said Perryman, “They’re like a convoy. They get a bunch of them together and go a long distance, so they’re less vulnerable, their location is less predictable.” Killer whales tend to remain in the Northern Pacific, pursuing other prey, when the gray whales travel south. So the newborn calves are safer.
But migration isn’t just about reaching the final destination.”There’s a lot of social behavior that goes on during the migration,” Perryman said, pointing to mating. “Late in the migration, there’s a lot of hanky-panky that goes on.”
The gray whales can’t remain in Baja for longer than the winter due to poor feeding opportunities. In February, the first to head back north are the newly pregnant females. They need to maximize their feeding time in order to collect calories for the next year’s trip. Calves nurse during the entire journey northward, drinking around 50 gallons of milk ” with over one third fat content ” every day. “She has to get heavy if she’s going to succeed,” Perryman said.
Because whales must surface in order to breathe, the northbound grays cannot access their feeding grounds until the winter ice cover melts, making gray whales susceptible to climate change. In warm years, the ice melts quickly and the whales are able to spend more time feeding. Changing prey distribution could force the whales to feed farther north; however, scientists aren’t sure how global climate change will affect the whales’ prey.
“Gray whales may benefit from a longer ice-free feeding period, but the overall effect is impossible to predict because the whole ecology of their feeding areas may change,” said Jay Barlow, SWFSC program leader.
In addition to estimating the population, Perryman uses aerial photography to assess the size of the whales. Fat whales indicate that the Arctic feeding grounds are well stocked, while skinny whales suggest that the ocean bottom community is not thriving.
“Gray whales are an example of a population that gives us a window into what’s happening in the Arctic, because they’re Arctic feeders,” Perryman said. “The health of that population depends on what happens in the Arctic ” and they have the common decency to swim right along our coasts.”