Posted on 24 September 2007 by ALOP
The appearance off the Orange County coast in recent years of blue whales, the largest animals that have ever lived, delights both whale watchers and wildlife scientists; few sights could be more majestic than the rise of an enormous tail above the water as the creatures dive, or the geyser-like spume of their breath when they surface.
The whales appear off the coast of Baja California in Mexico, San Diego and Dana Point each spring and often linger through the summer.
But one scientist who specializes in tracking blue whales says the recent shift in their travel and feeding habits is not necessarily good news. The largest animals in the ocean are totally dependent on one of the smallest: krill, a shrimp-like crustacean that moves in huge clouds beneath the water.
Although it’s too soon to be certain, the blue whales’ shifting patterns might be a sign that krill are depleted in their traditional feeding grounds farther north, says research biologist John Calambokidis of the Cascadia Research Collective in Olympia, Washington. More years of tracking and study will be needed to be sure.
Q. What is the focus of your research?
A. Almost all our work has been concentrated off the California coast, especially Southern California. We began that in 1986. When we first started tracking and identifying blue whales, it actually came about somewhat by accident. Our focus was humpback whales, but in the course of our humpback work we encountered blue whales in far greater numbers than anyone expected.
Q. How many blue whales are there?
A. Prior to commercial whaling, based on how many were killed in a short period, the estimate was that there used to be over 300,000 worldwide. Most of the whaling occurred during the 20th century because blue whales were so fast and large; they really couldn’t be caught or killed prior to the use of steam-powered catcher boats and explosive harpoons. The killing of blue whales was ended by the International Whaling Commission in 1966; by the time it ended, the estimated blue whale abundance was somewhere around 12,000. Ten thousand of that is supposed to be Antarctic. Since then, the estimates in the Antarctic have come up much lower than 10,000. There are a number of areas where we don’t have a good sense of how many there are.
The ballpark used currently worldwide probably numbers around 10,000. Even now, quite a few years after the end of commercial whaling, it still remains a tiny fraction of pre-whaling numbers.
The thing I always tie to that is that our estimate of the population that feeds off California, about 2,000 animals, is a subtantial portion of the estimated worldwide population, in a fairly small area. As far as we know, it’s the densest concentration of blue whales around today.
Q. How do you track them?
A. The main technique we use is photographic identification. We use photographs of the sides and back of the whale, around the dorsal fin. There are natural markings, variations in light and dark pigment, scars, and size and shape of dorsal fin – all are unique enough to allow us to reliably identify all these individuals if we have good quality photographs.
People like to make the analogy between humpback flukes, or markings on the sides of blue whales, as being like a fingerprint. But I don’t see near as much detail in a fingerprint than is available on a blue whale. We really do have a large amount of information and detail. It really is a reliable technique. It’s a really, really big fingerprint.
There are a number of other ways blue whales are being tracked. Oregon State University has had an active effort putting satellite tags on blue whales off California. We’ve used a different kind of tag – three different types of tags. They’re all aimed at looking at underwater behavior and vocalizations depending on the instrument. They measure a combination of how deep the whale is diving, temperature, all the sounds produced or heard, the body angle of the whale – the pitch and roll.
National Geographic has an instrument called Crittercam that records video films of what the whale’s doing. That’s been deployed over 20 times with blue whales. We learn a lot from the Crittercam video. (The tags) stay on the whale anywhere from a few hours to a few days.
Q. Any surprises?
A. One is that they were feeding deeper than expected. Where some of the research suggested they were diving to about 600 feet, we found they were diving closer to 1,000 feet.
The blue whale also produces one of the loudest sounds of any animal on Earth. It can be heard (for) hundreds or, with the right conditions, even thousands of miles. But we had no idea who was producing that sound and why. One of the things that came out of that is that the animals producing these extremely loud sounds are only the males. It appears to be something more related to mating than, say, locating prey or communicating about prey, which had been the speculation prior to that.
Also we were interested to see, How do blue whales approach their prey? They actually dive, usually, underneath this krill layer, then make vertical lunges to engulf the prey. They appear to be turning on their side or back as they do it.
Q. What did you learn in your recent research off San Diego?
A. We had a couple of different goals. (One was) to estimate population size.
The other goal is to look at their movement patterns – where they are going to, how far do they range to the north and south.
The whales that feed off California have been identified as those same individuals as far south as an area called the Costa Rica dome, which is down at about eight degrees north latitude. It’s an area several hundred miles offshore of Central America. We’ve identified them as far north as the Gulf of Alaska.
Q. Why do you think they have begun to appear off Dana Point?
A. I think the concern has been that krill abundance off California has declined. And there have been indications, especially up off Central and Northern California, of difficulties with reproduction and failure in some of the seabird populations that also feed on krill.
The other thing we have seen with the humpback whales that we study is more and more of a tendency of humpbacks to be feeding on fish rather than krill. Humpbacks are a bit more versatile species; they feed on more variety of prey than blue whales, which are considered strictly krill feeders.
Clearly one of the things that is attractive about Southern California (is that) we are seeing krill in areas off San Diego and off Dana Point, in areas where blue whales feed. Clearly there are large amounts of food and prey for them in these areas that they’re concentrating. We see that in the tag data.
Q. Could the shift in the blue whales’ patterns be a sign of trouble in the food chain?
A. It could be. Whenever you see a shift in the distribution of animals, it can be good news or it can be bad news. At this point we are trying to evaluate it, and I don’t think we have the evidence to do it. We’re seeing a broader distribution – how blue whales are distributed. Mostly we’re just more cautious in interpreting it as positive. It might be they are having to adjust to the fact that there are less krill.
Q. If krill is reduced, could it be related to global warming?
A. All kinds of things, including whales, depend on (krill). It is kind of a fundamental element; it has huge ramifications throughout the food chain. That is why we would be very concerned about anything suggesting declines in krill for predators – because it could have consequences for other species.
We’re trying to sort out whether that is part of global climate change or part of a normal cycle.