PBS - The Voyage of the Odyssey - Track the Voyage - MALDIVES
Risso's are unmistakable dolphins - they are large and robust with a blunt, squarish head that lacks the characteristic beak of most species. A vertical crease running from the blowhole and down the front of the melon is visible from the front. A long mouth line that turns up toward the eye gives the dolphin a conspicuous 'smile'. These are a distinctive species and a favorite of the crew.
Young Risso's are uniformly brown to almost black. By adulthood they are silvery-grey except for the dorsal, flippers and flukes, which remain almost entirely dark throughout their lives. The white face, extensive scarring and crisscross scratches that are indicative of this species, gives them a distinctly battered appearance.
Risso's are a pelagic species usually encountered in the deep waters of the tropical and temperate oceans. However, they can be found in coastal waters where the edge of the continental shelf is relatively close to land, as it is in Sri Lanka. This is also the reason why the normally oceanic sperm whale can be found in high concentrations relatively close to shore.
Extensive white scatches give this species a distinct battered
appearance. It seems possible that the heavy
scarring is a direct result of aggressive group mating behavior.
Photo: Chris Johnson
As we moved closer to the group, we noticed them swimming rapidly, even franticly as they chased a single animal in tight circles, their blunt heads burrowing down and pushing forward white capped bow waves. The dolphins clashed violently as bodies were jostled and pushed beneath the surface, several piled on top of one another in a writhing mass of heads, flippers and tail flukes. The otherwise still sea was whipped into a turbulent, frenzied mass of white water. We watched in amazement as the dolphins leapt clear of the water, half breached - slapped their heads against the surface, tail slapped and fluked. We drifted closer in the hopes of better observing this unusual flurry of raucous activity and to make acoustic recordings at close range.
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