The young bull bottlenose dolphin PC circles round and round a channel marker piling.
Tis the season for giving and getting, and I wish for you a gift so precious in its rarity that it keeps you in wonderment for years.
I got such a gift recently, compliments of our local dolphins’ unconscious tradition of giving me spectacular yuletide observations. This year’s gift was a lengthy demonstration of the rarest bottlenose dolphin behavior, called piling-peering, which looks like some maritime maypole manipulation.
On a perfect December day at sea, under misty skies like lace overhead, we came upon a quartet of dolphins. I nabbed a picture as mother dolphin P dashed away with her 16-month-old calf Paisley. Nearby, Jagger (after Mick Jagger) hunted in 10 inches of water, easily tracked by her dorsal fin peeking out of the water. She catapulted after fish and pinwheeled round them dramatically, leaving yawning mudplumes like rising smoke over submerged seagrass meadows.
The fourth dolphin was PC, a young bull bottlenose born in 2005 to the mother dolphin that departed so hastily; PC stands for P’s Calf. PC weaned from P at 16 months, the youngest weaning age to date, which means he’s been on his own for 5 of his 7.5 years.
He returns sporadically, most recently in spring 2012, as told in Dolphin Watch’s, Who goes home for spring break? Before that he visited in spring 2009. P and PC’s reunion was rare, but not the gift of which I speak.
The rare gift was PC’s piling-peering. Riveted on a channel marker piling, three different times he circled it for many minutes, curling by swimming on his side or putting his face close enough to bump his chin against it, and then swam a short distance away before returning. While circling, he periodically snapped his jaws but didn’t appear to hold anything in his mouth. What was he doing?
Broadly, piling-peering is a form of “object handling,” a term for any interaction between an animal and an item. Our local dolphins interact with two dozen objects, but usually briefly. This was among the longest object handling display we’ve seen.
Piling-peering is the rarest dolphin behavior. In nearly a thousand surveys, this is only the third time we’ve seen it. Stick did it some years ago, but she’s a known tool user. The first time was at the start of our study when PC’s mom P did the same thing to a piling not far from the one that so riveted her son this day.
In this rare behavior, the dolphin appears to be tracking something very closely that in turn appears to be moving, because all three dolphins circled the piling repeatedly. On their sides, they can use both of their eyes to study the piling closely. Is that what they’re doing? What for?
The piling that riveted PC’s attention was studded with three distinct layers of life, like neighborhoods with different needs for water.
Two were tough life forms that live on the piling where they were alternately submerged and exposed to air. The top layer, some 10 inches tall, was made up of barnacles that wrapped around the piling like white-topped chocolate candy we call Snow Caps.
The middle layer, perhaps a foot tall, was made up of oysters resembling fossilized potato chips anchored at treacherously perpendicular angles, their wicked sharpness belied by their gentle white and beige hues sprinkled with smudges of dull purple. At the current tidal level, the sea surface just licked the bottom-most oysters.
The third layer, gentler aquatic folk that cannot survive out of the water, lived permanently below the waterline: Brown-orange sponges, ranging in size from Brazil nuts to golf balls, peeked out from sprinkles of short life forms resembling clusters of maroon lace.
PC often faced the piling directly. The dolphin lower jaw or mandible sticks out further than the upper jaw, and dolphins often get scrapes on their chins like the skinned knees that perpetually adorned the kids of my day. I’ve often wondered how dolphins scrape their chins, and with the help of a shoving current, piling-peering may be one way.
PC occasionally snapped his jaws. Was he trying to gnaw the sponges, perhaps to get a unique taste treat like you mouthing and sucking on a green olive? Did he nibble on tiny citizens of the littoral city, miniature octopus or crabs desperately dashing across sponge fields, like you nibbling Chex Mix at a Christmas party?
Was he eating standard fare at an exotic restaurant, or teasing it? A six-inch fish scurried around the piling when PC did. The young bull may have been following the fish round and round the piling; if he’d wanted to eat it, he could have made short work of that intention.
I had to laugh when I thought about the handful of ganglia that fish call brains: The circling fish may have thought it was swimming along an endless straight sea wall instead of in small endless circles with a dolphin on its tail!
Was PC’s piling-peering a lesson at sea school? As a cross-modal being, you can use information from one sense and apply it to another sense, such as when you see a new Christmas present and then later, blindfolded, identify it by touch.
Dolphins are cross-modal too. They can be introduced to an object visually and then identify it later using echolocation. Is piling-peering some kind of sea school lesson wherein dolphins visually inspect the calcified creatures of the littoral city and then use their echolocation to learn acoustic signatures?
What do you think PC was doing?
Dr. Weaver studies wild dolphins under federal permit 16299, National Oceanic and Atmospheric Administration. Send her an email at firstname.lastname@example.org or visit her website www.dolphinsuperstore.com. NOAA advises anyone who sees a stranded dolphin in the Gulf of Mexico to call 877-942-5343 or 877-433-8299.