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Dolphin Watch
Attack of the oyster
By ANN WEAVER
Article published on Thursday, April 12, 2007
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![[Image]](/content_images/041207_out-01.jpg) |
| Photo by ANN WEAVER |
| Bottlenose dolphins are fond of shoving their weight around. This dolphin falls backwards on a submerged dolphin during a fight. |
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Technical reports of animal behavior in scientific journals are hygienic. Behavior is described dispassionately in the interests of clarity. None resonate with emotion.
So the technical reader is armed with knowledge but not necessarily prepared for the emotional impact of real-live behavior in nature.
Technical reports indicate that young male bottlenose dolphins avoid older males, especially pairs of bulls.
This story is a behind-the-scenes tour that reveals how avoidance is learned.
One misty mid-March morning, a small group of adults foraged off some mangroves. Females P and DD1 appeared intermittently. Bulls Edge and KK dove nearby. As they’re wont to do, they stopped, assembled side-by-side and headed to a new foraging site. They encountered several dolphins on the way.
I was alerted to the presence of new dolphins when KK assumed a standard stationary posture: The front half of his body floated on the surface while his back half hung vertically. He pulled his head back and peered above the water (an intriguing phylogenetic puzzle considering the superior fact-finding facility of echolocation).
But then he chuffed. Chuffing, a strong cough-like vocalization, is not part of the stationary ‘dolphins ahead’ posture. Maybe I should’ve expected trouble. But in my experience, chuffs mean several things, not just trouble.
Among the new dolphins, mothers Face and Split (with calves) approached directly. The two groups met and mingled. We haven’t seen Split or son Steve since New Year’s Eve. The return of long-lost dolphins signaled the return of spring.
There were two young adults near the new group, male Oyster and female Bet. Their approach was ambivalent. They approached about half way, angled off and milled. Another clue.
The adults swung by the boat with several sneak-a-peaks (another clear use of vision). One by one, they seeped towards shore.
Not Oyster and Bet. They approached the boat instead, weaving around it elaborately for several minutes. They even positioned to bow-ride. Not extraordinary behavior, but unusual. I keep my boat boring and they, as intended, eventually lost interest and headed toward the others.
Small subgroups of two or three began a slow southward trek along cement sea walls of waterfront homes. Massive male Edge swam with P and DD1. Hefty KK swam with Face. As Baby Face bounced around, Face altered their course to stay within 30 feet of Baby Face; she still keeps her baby close.
Passing slivers of water called fingers, some poked in briefly before rejoining the trek. They were done feeding.
Oyster zipped up one finger. He punched into the mushy sand bottom, leaving a tan mudplume behind. Edge followed him into the plume.
Suddenly Oyster shot skyward. Edge followed, body slamming Oyster and knocking him sideways. Still airborne, Edge rolled and crashed backward down on Oyster. After a moment of ominous silence, they did it again.
Footprints bubbling to the surface revealed Oyster’s headlong race down the finger. Edge surfaced with several mighty chuffs that shot cones of vapor into the misty morning air. The adult females passed this drama without pause. Edge hurried after them into the bay.
Oyster’s footprints became a trail of mudplumes, a line of tan circles in green water.
We normally equate mudplumes with feeding. But dolphins who socialize in shallow water create mudplumes too.
Plus, how strange to switch from fighting to fleeing to feeding in a heartbeat.
What explained his mudplumes?
One, Oyster could’ve been hurt by Edge’s brief but unambiguous attack. Do you ever rub a bumped part of your body to reduce bruising? Do hurt dolphins rub the seafloor like you burrow an aching head into a distracting pillow?
Two, Oyster might’ve redirected frustrated aggression onto the seafloor. Birds are masters of redirected aggression but it’s not exclusive to them. Aroused birds unable or unwilling to attack the source of their anger will rip at foliage furiously as if suddenly overcome with frantic hunger. Apes who run screaming through the rainforest, dragging branches or hurling sticks, are also venting frustrations safely.
Deep in the winding waters of the finger, beyond visual and probably acoustic range of the others, Oyster slowed down then. But his mudplumes continued.
Edge’s attack was anything but dispassionate. He clearly separated Oyster from potential mates. He gave a clear lesson on how young males learn to avoid older males. Think of poor Oyster if KK had joined the attack.
How effectively technical reports sanitize fight and flight.
Read technical reports for their valuable information. But get your dramas somewhere else.
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, April 12, 2007
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