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Dolphin Watch
Pretty pirates
By ANN WEAVER
Article published on Thursday, May 10, 2007
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![[Image]](/content_images/051007_out-01.jpg) |
| Photo by ANN WEAVER |
| This tern steals a fish from a feeding dolphin. |
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I went to Treasure Island’s City Hall the other day. A larger-than-life pirate statue glares out from a corner. Its realism shot me back to when these islands were haunted by the rough tough stinky thieves we’ve romanticized over time.
What was pirate culture really like? Strewn across vast seas and scattered islands, how long did it take for their horrendous habits to spread to different groups?
In our current culture, the darkest news is the most attractive. If that’s always been a human habit, it probably wasn’t hard for maritime mugs to set the pace with their dark deeds but it probably took awhile.
Given the relentless development of these coastal islands, the chances of finding buried treasure are pretty remote. Yet I was on a treasure hunt of another kind, one both surprising and unsurprising.
Back at work, I dug through a vat of 5,000 photo-identification photographs from this spring’s research surveys of dolphins. Photos are some of the data that help me monitor bottlenose dolphin distribution, abundance and behavior to see if anything changes during the massive reconstruction of John’s Pass Causeway.
I looked for pictures of birds, terns, sprinkled among spring surveys. Small and white with mottled black caps, terns hunt for food near the sea surface like pelicans, plunging from the skies to snare fish near the surface. They’re nicely equipped for their niche with long orange beaks that serve as vices.
Of late, however, these pretty pirates have become laced with larceny: They seem to be developing the new habit of stealing fish from dolphins.
How? Dolphins sometimes drive their fish food to the water surface, a maritime dead-end that eliminates an escape route from fleeing fish. Normally, this is a good idea, at least before terns began exploiting it. Terns have learned to hover over feeding dolphins, lunge at the last moment and literally grab the fish before the dolphin does.
What do the dolphins do? Some, like adult female Q, lunge forward either at the plundering pirate or just completing the momentum of their feeding launch. Other dolphins like Stick, P and Oyster whap the surface with a tail slap as if in understandable ire.
The thievery began in early spring. The embezzlements are increasingly frequent. So the question is whether a handful of talented terns rob more often or a growing number of terns are learning to rob. Observations of scattered groups of foraging dolphins accompanied by similarly scattered terns suggest the latter.
The absorbing question is whether this is another case of animal cultural transmission.
The animal behavior literature includes intriguing examples of new habits spreading across conspecifics (members of the same species). The clearest occurred among Japanese macaques (monkeys) living on an island. Every day, scientists threw yams and wheat (seeds) on the beach for the monkeys to collect and consume. Imagine eating an apple right off the beach. Gritty. This apparently occurred to a juvenile female named Imo, who solved the problem by carrying her yams to a freshwater stream and washing them off.
If Imo were human, we wouldn’t think twice about her innovation. But we too rarely give animals credit for using their brains creatively or other animals learning from innovators.
Under close scrutiny by Japanese scientists, most earnest and capable observers, younger monkeys picked up the habit first. Tellingly, the oldest males never did. Eventually, most of the monkeys were washing their yams.
Three years later, Imo raised the bar further. She solved the harder problem of separating sand from the seeds. She carried two fistfuls of sandy seeds, certainly an innovation for a quadruped designed to walk on four limbs, and tossed them into the water. The sand sunk. The seeds floated. This habit spread too, albeit slowly, across the colony.
A British example of cultural transmission came from the time when milk, in glass bottles with light metal tops, was delivered and left on doorsteps. British birds learned to pry open the metal top with their beaks like you prying the hygienic seal on a bottle of aspirin with a pencil. This habit too spread across the land.
In the midst of construction clamor, we may not find buried treasure on Treasure Island. Instead, a treasure of white jewels may be glistening down from the skies before our very eyes. Science is always good for buried treasures.
And like the gracious citizens of Gulf Boulevard themselves monitoring anything that threatens the quality of their dolphins’ lives, I’ll let you know when the dolphins develop their counter-measures.
Dr. Weaver studies wild dolphins under federal permit GA1088-1815, National Oceanic and Atmospheric Administration. Send her an e-mail at acweaver@tampabay.rr.com or visit www.dazzlingdolphins.com.
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Article published on Thursday, May 10, 2007
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