Dolphin Watch
I knew dolphins played catch, but squash?
By ANN WEAVER
| Article published on Thursday, June 18, 2009 |
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| This dolphin is about to squash another dolphin just under it. But that’s not the Squash this author is wondering about. |
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Bottlenose dolphins are playful. While games are often solitary, a surprising number involve multiple dolphins.
Humans play games all the time. So it’s hard to remember that games require coordination and theory of mind, the latter the state of “I know what you’re thinking”.
One coordinated dolphin game is Toss the Eel. Dolphins form a rough circle and toss an eel to each other.
Animal behaviorists interpret animal behavior with a hierarchy of hypotheses. The hierarchy lists explanations for behavior from simplest to most complex. We settle on the hypothesis best supported by data regardless of its complexity, once we’ve seen the behavior enough to explain it.
A simple explanation of Toss the Eel is that it isn’t a coordinated game at all. Maybe eels taste terrible. Maybe the ‘game’ is just a series of repeated rejections, much the way my parrot immediately throws food out of her bowl that doesn’t meet her approval.
If each dolphin did this with the eel, it would look like a coordinated game. On the other hand, a complex explanation is that the dolphins are in fact playing a game with all the cooperation, coordination and theory of mind that games imply.
What about a game like Keep Away with seaweed? Dolphins don’t eat seaweed. We can’t use the explanation of tossing away unappetizing food.
When one dolphin swims away with a hunk of seaweed trailing from its mouth, other dolphins give chase and the seaweed is transferred from dolphin to dolphin, it looks very much like a coordinated game.
We know dolphins are quite capable to coordinated behavior. They work together to herd a school of fish into a tight frantic ball. One dolphin after another launches through the school, eating all the way.
The school eventually scatters. So the dolphins stop eating and herd the school again. A simple explanation is that each dolphin is doing what it would do by itself but when done as a group, it looks more coordinated than it is.
But the fact that dolphin take turns launching through the school means they have a sense of sharing. Otherwise, the biggest or hungriest would get the fish. A complex explanation is that they are indeed working together for the general good with all the cooperation, coordination and theory of mind that this implies.
Lions, wolves and killer whales do the same thing.
Other coordinated behaviors are really tough to explain. Spotted dolphins in the Bahamas do a behavior called a group roll. The only way to describe it is a group swarm, like a ball of mating anacondas.
The dolphins squash up against each other and roll around each other, maximizing physical contact without having sex. Curiously, the Bahamian dolphins group roll in a vertical position like five people all trying to slow dance together.
Our Florida dolphins did a group roll at the end of a recent steamy summer survey. It turns out they group roll in the horizontal position.
It started with intense interactions among bulls swimming with females, one with a brand new calf. Maybe it’s the calves. Maybe it’s the females. Either way, bulls around new babies get very excited and express it with riotous displays of love and war.
Bulls N, Pepto and Cane swam with Schnoz, Bet, Split and Cleft (with new baby). We got there during a general ruckus followed by a sprint to the shallows. Between episodes of apparently quieter swimming, various wads of dolphins erupted into intense bouts of “socializing.”
It was hard to tell if the bulls were focusing on each other while occasionally spilling into the female ranks or whether females were purposely involved. It was also hard to tell if this was the general ‘good-natured violence’ of dolphin interaction or something more serious.
I built my hierarchy of hypotheses one rung at a time.
After many minutes, they switched to group rolls. Quieting, they literally squashed against each other, swimming shoulder to shoulder as it were, and moved between sea floor and surface like one dolphin instead of eight. The switch in rhythm and intensity was almost audible.
When submerged, they obviously made direct contact with the hard-pack sea floor. This was indicated by large mudplumes that rose to stain the surface with a scattering splotch of tan sand after each submergence. A simple explanation was that each was rubbing on the sea floor to groom itself. A complex explanation was that this was coordinated activity using the hard sea floor to hold someone against, for good or bad.
At the surface, they did something rare: They swam in tight circles like a real live maritime merry-go-round.
I added more rungs to my hierarchy of hypotheses.
Circles often mean tensions. Competitive sea lions circle each other underwater. Competitive carnivores do the same thing on land, resembling the circling of two prizefights vying for the chance to land a punch.
But that doesn’t explain dolphin group rolls because the dolphins circled as a group. The circle they traced was very small. They circled until their movements slowed to the point of sleepiness.
A simple explanation was the admirable spontaneity of dolphins: Tensions released for the moment, they simply rested after exertion. We trailed them for an hour to see if conflict re-erupted or they suddenly ‘woke up’ like they do when snoozing. Neither did. Several groups of new dolphins even cruised through (including the social circumstances of more mothers with new calves that excites the bulls). None elicited the former excitation.
While the simple explanation of rest might suffice, we know dolphins are very group-minded, excel at cooperation and coordination, and apologize after conflict. Whether among humans, primates, or dolphins, apologies are reassuring. Apologies reinstate the harmony of a relationship hurt by conflict.
The highest rung of my hypothetical ladder of explanations is that we witnessed a coordinated group apology with all the cooperation, coordination and theory of mind that this implies.
The next question is: How many group rolls to we need to really answer the question?
Dr. Weaver studies wild dolphins under federal permit GA1088-1815, National Oceanic and Atmospheric Administration. Send her an e-mail at dazzled@tampabay.rr.com or visit www.dazzlingdolphins.com.
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Article published on Thursday, June 18, 2009
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