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LatestPhoto
Two whales rest at the surface after a 45 minute feeding dive.
Photo : Chris Johnson

November 7, 2003
Whales in Mauritius
Real Audio Report
  28k


Log Transcript

This is Genevieve Johnson speaking to you from the Odyssey in Mauritius.

Last week, the Odyssey crew left Port Louis looking forward to spending a couple of weeks at sea with whales. Local fishermen told us that whales are found close to shore on the west coast. This kind of information is invaluable; we have learned over the years that locals, particularly fisherman, are always the best source of information on where to find whales.

The islands that make up Mauritius are only the very tips of enormous mountains rising from the ocean floor, similar to Hawaii, the Galapagos and the Azores. Due to their volcanic origin, the underwater slopes drop away suddenly and steeply, plummeting thousands of meters. Deep ocean currents hit the base of these slopes, forcing nutrients to the surface. These nutrients form the basis of a productive oceanic ecosystem that includes the sperm whales favored prey, squid. As a result, sperm whales are often found foraging around volcanic islands.

Within 30 minutes of leaving Port Louis, we deployed our acoustic array - an underwater microphone we use to find and track whales. Less than 3 miles from shore, in over 2,000 meters of water we had our first acoustic detection. One whale became three, then five and then twelve - we were surrounded. We tracked the whales in slow circles all night - the channel lights marking the entrance to Port Louis were in constant view.

Our first sperm whale sighting coincided with a dazzling sunrise and a lively band of Pan-tropical spotted dolphins, who joined us briefly off the bow. This first group of whales consisted of approximately 25 - 30 animals, including at least one adult male, several small clusters of sub-adults and juveniles, and one mother/calf pair. Young sperm whales, particularly newborn calves are unable to dive deeply and are forced to remain close to the surface waiting for their mother to return. We watched one very small calf left alone at the surface, barrel at top speed toward a group of three surfacing adults about 200 meters away. Its comparatively tiny head, covered in remora fish bursting almost vertically out of the water, as though it was yet to realize its blowhole is situated on top of its spermaceti organ and therefore it only need lift it slightly out of the water.

LatestPhoto
Even when sperm whales surface some distance apart, they seem compelled to join one another and swim downwind side by side.
Photo : Chris Johnson

The whales were feeding in a relatively small area off the coast, moving back and forth along the 2,000-meter bathymetric contour line. We are extremely excited to have found so many whales so soon in our journey.

Mauritius is notorious for its high winds and exposure to weather moving up from the Southern Ocean. However, for now, we are enjoying unusually calm seas. We decided to take advantage of the fair conditions and left the west coast in order to survey the northern and eastern side of the island. Our survey on the windward side was relatively uneventful, however, once we rounded the southeastern tip, we were among whales once again.

Our first encounter was with a large, lone male. We watched the animal fluke (dive) before tracking him through an entire dive cycle. The whale stayed submerged for a staggering one hour and fifty-seven minutes, his loud, regular clicks resonating through the speakers in the pilot house.

Diving for one hour is not uncommon for mature males, but we have certainly never recorded a sperm whale dive close to 2 hours - a remarkable achievement for a mammal. Upon his return, the whale erupted through the surface, the crew stared at the fifty-foot animal in complete awe, wondering what he had just encountered on his journey into the abyss.

Like Herman Melville, we pondered the life history of this inexplicable creature.

    "That head upon which the upper sun now gleams, has moved amid the world's foundations."
    - Herman Melville, Moby Dick, 1851.

LatestPhoto
Satiss Conhye, our observer from the Ministry of Fisheries in Mauritius, photographs his first sperm whale.
Photo : Chris Johnson

Later in the afternoon, we sighted a group of seven animals at the surface. Between feeding dives (lasting an average of 45 minutes), sperm whales rest quietly at the surface for 8-10 minutes. During these periods, even when surfacing some distance apart, the whales seem compelled to join one another. Usually if they emerge within 400 meters, they will swim toward and alongside their companions and drift downwind before fluking simultaneously to begin feeding. The long, deep foraging dives are a major feature of sperm whale behavior, taking up about 62% of the animal's life.

Today, the crew of the Odyssey is with sperm whales of the southwest coast. In the morning, the ocean was calm and the breeze light - we watched the whales blow and rest against a backdrop of volcanic splendor. It is difficult to imagine a more serene setting. In contrast, the afternoon brought the trade winds from the south and the ocean quickly whipped into a frenzy of whitecaps. Such windy conditions are often associated with breaching and today was no exception. Most parts of the sperm whale are only seen briefly and from an above the surface perspective, the enormous nose and jaw during a spy-hop, the tail flukes before a deep dive and occasionally the belly during a roll. However we are sometimes afforded the brief but spectacular opportunity to view the entire body when the animal launches itself skyward during a breach. There is scarcely a sight in nature to rival 45 tons of flesh bursting through the surface before twisting and crashing back to sea, in an explosion of white water. Such experiences are burned into the memory for life.

Since leaving Port Louis, we have been with whales every day. The days are exhilarating, but also incredibly long. The entire crew is on deck from dawn until dusk, with little time for a break. We alternate running inside for a drink, a snack or to re-apply some desperately needed sunscreen. While the night hours are filled with watches and tracking whales so we are ready to begin sampling at first light.

LatestPhoto
After seeing and photographing his first whale, Satiss smiled joyously stating - "This is amazing!"
Photo : Chris Johnson

By the end of the first week, we estimated the number of sperm whales seen at the surface or acoustically detected at around fifty. The crew is tired with most of us having far too much exposure to the sun; yet those special moments and unforgettable encounters with whales, combined with the opportunity to increase the knowledge base related to marine mammals in Mauritius waters is enough to keep us going. The crew would not have life any other way.

Links:

References:

  • Sperm Whales - Social Evolution in the Ocean.
    Hal Whitehead - The University of Chicago Press, 2003.

Written by Genevieve Johnson

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