Dr. Mridula Srinivasan, NOAA

ANIMALS IN SEA HISTORY

Dusky Dolphins

Scientific Name:
Lagenorhynchus obscurus
Lifespan:
30 years
The dusky dolphin is known for their energetic and acrobatic jumps. They are inquisitive and often approach boats.
 

illustrative cartoon

by Richard J. King

The French sailor Bernard Moitessier is perhaps best known for sailing alone a full one-and-a-half times around the world, nonstop, in the Golden Globe Race of 1968–69. He later published The Long Way, a book about his experience. It is one of the finest sea stories ever composed, a masterpiece in nature writing in which he describes a spellbinding experience with dolphins.

Aboard his boat Joshua (named after the first solo circumnavigator Joshua Slocum), Moitessier was sailing a route that had taken him from England around the Cape of Good Hope, across the Indian Ocean, south of Australia, and was about to enter the South Pacific just below Aotearoa New Zealand. Among the books that he read underway was Robert Merle’s The Day of the Dolphin (1967), a science fiction novel about marine mammal intelligence and a biologist, based on the real-life figure of John Lily, a researcher who studied water immersion, hallucinogens, and dolphin-human communication.

map and dolphins

Dusky Dolphins leaping off the coast of New Zealand, near Kaikioura.

As Moitessier and Joshua were nearing Rakiura (Stewart Island), he knew that submerged rocky shoals, called “South Trap,” extended far out beyond the island. Though it was mostly overcast, he managed a sun sight with his sextant and was able to fix his position with some confidence. He continued sailing along with a steady favorable breeze, making sure to give the shoals a wide berth. Once he got past the shoals, he would be eastbound in the Pacific, free from worrying about any more land for thousands of miles.

The sky overhead filled in with clouds, but the sea remained relatively calm. The wind held as he sped along, eager to pass this last hazard, when he noticed a rush of more than 100 dolphins approaching, then schooling around his boat. He could hear clearly their “familiar whistlings.” These were likely dusky dolphins (Lagenorhynchus obscurus), who have small snouts, black backs, and white bellies. Dusky dolphins are smaller ocean dolphins, known around Aoteaora as being especially gregarious, vocal with their squeaking and whistling, and they seem to enjoy interacting with boats and people along the
coast. Describing these animals near Kaikioura, local whale watch expert
Barbara Todd wrote that “even ‘hardened’ whale watchers…end up being totally captivated by the Duskies.”

But this dolphin behavior was something Moitessier had never seen before in any dolphin anywhere. He wrote: “A tight line of 25 dolphins swimming abreast goes from stern to stem on the starboard side, in three breaths, then the whole group veers right and rushes off at right angles, all the fins cutting the water together and in the same breath taken on the fly.”

The long Way by Bernard Moitessier

Moitessier watched the dusky dolphins repeat this right-turning behavior over and over. He sensed that they seemed agitated, even “nervous.” Normal dolphin behavior would be to swim on both sides of his boat or plunge in his bow wake, especially since he was sailing along so swiftly. In this sighting, among the huge school, a smaller group swam alongside his boat and continued to sharply turn right, to starboard, over and over again. The dolphins repeated this group turn about ten times.

illustration of a Dusky Dolphin

Disoriented by the calm seas and uniform gray sky, Moitessier hadn’t noticed until he checked his compass heading that his boat had turned with the shifting winds by 90 degrees and was steering directly for the rocky reef of South Trap! He quickly altered course, following the dolphins, after which the school stopped turning but continued to swim alongside. The entire school stuck around, mostly on the starboard side of his boat. Then one of them leaped out of the water three times, spinning in the air—a behavior common to dusky dolphins and a few other species. Moitessier could not help but interpret this to mean that the dolphin was celebrating his understanding of their warning to alter course to starboard, away from the reef. Although he was tempted to steer back toward the shoals to see what would happen, he wrote that he was afraid to ask for too much, to probe his fairy tale too hard: “I can’t risk spoiling what they have already given me.” The dusky dolphins, it seems, had saved him from an impending shipwreck.

The dolphins continued traveling beside him, at times looking up at him, and kept playing around Joshua for about two hours—longer than he had ever been surrounded by dolphins in all his years at sea. Even when the main group left, two dolphins stayed with him, one on each side of the bow. “Two fairies in the waning light,” they swam alongside for another three or so hours, until after he had cleared the South Trap and entered the safety of the wide open South Pacific.

Bernard Moitessier sailboat

Bernard Moitessier sailing in his boat Joshua during the 1968–69 Golden Globe Race. Photo courtesy of PPL Media Ltd.


For more Animals in Sea History see www.seahistory.org or educators.mysticseaport.org. If you enjoy this feature, be sure to look out this May for the release of Ocean Bestiary: Meeting Marine Life from Abalone to Orca to Zooplankton, a revised collection of over fifteen years of this column!

Did You Know?

Ship Worm Clam

Damage to wood by the shipworm clam was often extensive enough to sink a ship!

As a tiny larva floating in the ocean, the clam lands on the hull or piling of a ship and immediately begins to grind into the surface of the wood with its shells.

How did Christopher Columbus and other mariners protect their ships from the shipworm?

Learn more at Ship “Worm” Clam