MatTag Sailabout

"We've got a whale!" Jim calls from the helm. "Straight ahead."
Glen and I scramble to the foredeck. I call back over my shoulder, "What kind is it?"

"I didn't get a good look," Jim answers. "Maybe a humpback."
Glen and I look down at the smooth slick of ocean left where the whale blew seconds earlier.

The whale surfaces and blows again. Something is different from a humpback. I am looking through my camera viewfinder, so I am slower to put the puzzle pieces together: dorsal fin low and rounded, fore-body more flat compared to a humpback, whale acts like a humpback that is resting or sleeping. On the second blow, I notice the skin. Dark and folded, crenulated, like a fan folded into leather.

"It's a sperm whale!" I shout for Jim to hear. "Glen, it's a sperm whale!" I repeat as if he hadn't heard my first exclamation.

"Cool!"

Glen is next to me at the bow pulput. The whale surfaces and blows again, barely moving forward.

I have seen this species before, in the North Atlantic, 100 miles off of Halifax, Nova Scotia. Three decades ago I spent 10 days helping Hal Whitehead and his graduate students collect the first biopsy samples for genetic studies from sperm whales.

"Jim, turn to port," I say. We need to turn now to avoid a collision. This whale is barely moving.

Shortly after sunrise that morning, we left a small cove on hour north of La Paz, on the southeast end of Baja peninsula. We were finally starting our journey to mainland Mexico.

When he saw the whale ahead, Jim slowed the boat from our 7-knot cruising speed. The sperm whale - a species not commonly seen in this channel - surfaced right in our path. We'd not seen any blows earlier, probably because he'd been down for a long time.

Sperm whales are the largest of the toothed whales, but this individual is small, about 30-35 feet long. I'd guess it is a young male because it is alone. Most females stay with their mother's group for life, an extended family that roams the mid-latitudes and up to about 40 degrees north and south. This species has a social structure nearly identical to that of African elephants. Young males eventually splinter off from their mother's group to travel in bachelor herds, or later, alone. Except of course during the breeding season when successful males join and defend a harem. Bulls grow to 60-feet and 60 tons, or more, whereas females top out around 36 feet and 27 tons.

Sperm whales can dive as deep as a mile. Well before that depth, our rib cages would be crushed by the pressure. To figure out the pressure at a mile deep, we add one atmosphere of pressure for every 10 meters in a mile. At a mile down, that's 1,700 times the pressure your skin and body are currently experiencing.

How do these whales dive so deep without damage? Sperm whales exhale before diving, so there's not a lot of air in their lungs to start. And, their ribs are floating, so they don't snap in two like ours would under much less pressure.

Deep diving whales have inherited other ways to avoid problems while diving. For example, the air in the most distal and delicate pockets of alveolar tissue, where gas exchange occurs, is pressed out of these spaces first by the increasing pressure. This air moves up into the thicker branches and trunk of their upside down 'lung tree' (in which the leaves would be the thin-walled alveoli).

The specific microstructure of a sperm whale's lungs sequentially pushes the air from the smallest active air exchange chambers into larger dead air spaces, where the thicker tissue can collapse together and re-inflate later without incident, eliminating the potential for embolisms. The volume of air present in the lungs at the surface steadily decreases as the pressure increases; on the way back up, the held air will return to its original volume.

Sperm whales can be recognized from long distances by their blows. The blow is angled forward and to the left because of their unusual head and nasal passage anatomy, a fact well known to - and used by - whale hunters.

The sperm whale off our bow breathes about 15 times, letting us get a good look. A humpback usually replenishes its oxygen stores in three to five breaths, but then they are shallow divers, rarely exceeding 20-minutes underwater.

The whale is now ahead of us several hundred meters. We watch until it dives. As he tilts down almost vertical to the water, he raises wide, drooping flukes. Our depth meter says we are in water 720 feet deep.

Will the whale head down and down and down, beyond where light penetrates, to search with pulsed echolocation clicks for squid? Or, is he traveling north, up the Sea of Cortez to find better feeding grounds?

Whatever his destination, we feel fortunate to have crossed paths.

[For more photos of the sperm whale, check out the Gallery.]