Returning under water from a beach dive to the submarine canyon off La Jolla Shores, my dive buddy and I were closing in on the Beach & Tennis Club when, in turbid water about 10 feet deep, a huge, shadowy form took shape some distance in front of me. It grew more imposing as it made a beeline toward me. Now only a couple of feet away, we made eye contact, wherein the behemoth turned away to reveal its bulk more vividly before it swam off into the murk.
In such a situation, the mind races to make sense of what is happening. As this was late June, I was momentarily confused. Was this the biggest sea lion I’ve ever seen? I came to my senses when the dark dirigible noiselessly cruised past me. Once the resulting pressure wave rolled me over, I glanced back to see the fluke. No doubt, I had a close encounter of the gray whale kind.
Sighting a gray whale (Eschrichtius robustus) this time of year is unusual. Typically, grays dwell in their Arctic feeding grounds from May to October, then travel to their breeding and birthing lagoons in Baja, California where they reside from December to March. Their nearshore lifestyle is one reason many scientists view this species as the equivalent of a living fossil. Another reason is their physical structure, as baleen (used as a sieve to separate food from mud) in the lower jaw is much simpler in grays than in that of other baleen whales. And by and large, grays act as bottomfeeders, suctioning the shallow sea floor like a vacuum cleaner, then straining out small crustaceans.
In contrast, other baleen whales feed mainly in the open ocean on plankton. Also, gray whales are slow movers, averaging 3 to 4 miles per hour as opposed to other baleen whales that hum along two to three times faster. Yet other scientists reject the label “primitive,” suggesting instead that grays derived these characteristics to meet their specialized, highly evolved needs. Both views underscore the puzzle of gray whales to researchers.
After coming together face mask to face with the gray, my dive buddy and I ascended to the surface to gasp about our thrilling exchange with the gentle giant. I recalled the moment the gray and I locked eyes on each other. We agreed the whale was a young juvenile about 15 feet long. Its skin, with texture resembling that of a hard-boiled egg (sans shell), was charcoal colored and interrupted by scattered white markings and small white patches of hitchhiking barnacles.
Scanning the surface, I spied a spout north of us, signaling that the whale was continuing its journey. A whale’s spray is plainly visible because it is made up of oil droplets as well as water vapor. When spewed, the foamy mix is easy to see. The oil’s purpose is to prevent the “bends” (a painful and potentially fatal condition caused by nitrogen bubbles forming in the blood when a scuba diver surfaces too quickly). Though blubber absorbs some of the gray’s nitrogen, the rest is trapped in the nasal sacs and sinuses, which is expelled with the oil when the whale spouts.
The calf’s mother was out of sight but I hope she was nearby, because juveniles must nurse for six to seven months. Even without nutritional need, youngsters require an experienced guide for safety and navigation. Not only is the nearshore environment notorious for generally poor visibility, grays must find their way without the means to make high-frequency sounds for echolocation, like some other marine mammals. Instead, they may rely on memory along with their highly developed hearing; grays boast an auditory nerve relatively larger than in other mammals.
Recent research suggests that grays employ passive acoustic navigation using ambient noise, such as that made from surf and rocks breaking the surface as clues for directional guidance, and boats and animal sounds to avoid danger. Noise that undermines their hearing, such as sonar, can threaten their ability to function and, over the long term, to survive. By the Navy’s own estimates, even 300 miles from the point source, sonic waves can emit 140 decibels ” a hundred times more intense than the noise aversion threshold for gray whales.
” Judith Lea Garfield, biologist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. www.judith.garfield.org. Questions, comments or suggestions? E-mail [email protected].
