Leftover Whales

By Joe Eaton
Tuesday July 12, 2011 - 09:25:00 AM
Mother and calf: grey whales in a Baja California lagoon.
Jose Eugenio Gomez Rodriguez (via Wikimedia Commons)
Mother and calf: grey whales in a Baja California lagoon.

If you have to get scooped, it might as well be by David Perlman. 

How it happened: I try to visit the UC Berkeley campus every Cal Day to scout for possible stories. The UC Museum of Paleontology, Museum of Vertebrate Zoology, and Jepson Herbarium are all good sources. Some faculty member or grad student is likely to be doing interesting research on a local organism. 

This year I got into a conversation with UC professor David Lindberg about his work on the California gray whale, including some paleohistory and behavioral observations. It sounded like column fodder. I looked for his recent publications but found nothing related to what we had discussed, so filed the idea away for future reference. 

Then last week his research article, co-authored with Nicholas Pyenson who is now with the Smithsonian, was published online by the Public Library of Science. Good stuff. And kudos to PLOS for its open source policy. It’s always frustrating to find some fascinating piece of research hidden behind a paywall. 

Before I could knock a column out, the Chronicle beat me to it. Perlman had a front-page story on Monday with the gist of the Lindberg-Pyenson paper. For anyone outside the Bay Area who may be reading this, David Perlman is a living legend in science journalism. He’s somewhere around 92 and still going strong. 

Started with the paper in 1940, was present when the hydrothermal deep-sea vents off the Galapagos were discovered in 1964, broke the AIDS story in 1981. Recipient of the Helen Thomas Award and has two science journalism awards named for him. 

I looked over his whale piece very carefully. He didn’t get anything wrong. Of course not. 

Anyway, there were a few crumbs of fact left over, so I thought I’d see if I could expand them into a Planet piece. 

The gray whales that migrate up and down our coast are one of three original populations. The Atlantic gray whales were wiped out about 400 years ago, probably by those enterprising Basques. The western Pacific grays are endangered, down to a few hundred. Our grays were also hammered by whaling, although the toll is a matter of controversy. Their predictable journeys between their feeding grounds in the Bering, Chukchi, and Beaufort seas and their calving groups in the lagoons of Baja California made them easy targets for shore-based whalers. Once protected, they rebounded to a current population on the order of 20,000. 

Their natural history was thought to be reasonably well known. Other baleen whales, including blues and humpbacks, filter pelagic crustaceans and small fish from the water column. Most grays, though, are bottom feeders, hoovering up benthic crustaceans called amphipods and polychaete worms from the seafloor muck. And all grays were believed to take part in the annual migration. 

This picture was muddied by the discovery of apparently resident gray whales off the coasts of British Columbia and Washington State in the 1960s and 70s. This is a small segment of the total population, about 155 individuals as of 1998. Instead of benthic organisms, the residents—like typical baleen whales--were eating a mix of pelagic species, including crustaceans, fish, and squid. 

This behavioral flexibility intrigued Pyenson and Lindberg. It occurred to them that the nearshore foraging habitat used by contemporary gray whales might not have been available to their ancestors during the Pleistocene glacial maxima, when a huge amount of water was locked up in ice and you could have walked from Berkeley to the Farallones. Comparing the extent of Pleistocene ice at the northern end of the whales’ historic range with estimates of carrying capacity, they concluded that there would not have been enough shallow seafloor to support the present population of grays, let alone a conjectured larger pre-whaling population. 

Maybe the whales, or at least enough of them to squeeze through the genetic keyhole, switched from benthic to pelagic food sources when the ice made their normal routine impossible—and did this not just once but multiple times, through the whole sequence of glacial cycles. 

Pyenson and Lindberg raise the issue of whether the resident whales of the Pacific Northwest have a special genetic heritage that enables pelagic filter-feeding, as with the different specialist populations of orcas. There’s no data one way or another for grays. It could be that neither foraging strategy is all that hardwired. Consider the Canada geese that at some point realized they didn’t really have to migrate, given the alternative of hanging out on a golf course all year. 

In another case of cetacean opportunism, the authors report that single gray whales have been showing up in the Mediterranean lately; one made it all the way to Israel in 2010. Were the Atlantic and Pacific populations once linked through ice-free Arctic corridors? The Great Thaw is bad news for polar bears and other high-latitude species, but it may have reopened a door for the gray whale.