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As an air-breathing mammal, the sperm whale must load its oxygen stores and expel carbon dioxide at the surface before another long, deep dive.
Photo: Chris Johnson

June 8, 2001
The Dive Cycle of the Sperm Whale
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Log Transcript

This is Genevieve Johnson speaking to you from the Odyssey.

Sperm whales may dive to depths of more than 1000 meters in their search for prey. Between deep dives, a sperm whale ventilates its lungs through a single blowhole orientated on the top left side of the head. While the whale is at the surface, it recovers for about 10 to 15 minutes after a dive, blowing heavily every 10 to 15 seconds. When the oxygen stores in the blood and muscle tissue are replenished, there is sufficient oxygen to allow the whale to hold its breath for the next 40 to 50 minutes. Sperm whales repeat this cycle with varying intervals, throughout the day and night. Visiting scientist, Peter Teglberg Madsen, discusses the dive cycle of the sperm whale.

Peter Teglberg Madsen

At the beginning of its almost vertical descent into a dark and cold world, the whale arches is back and flukes. The swimming speed is a moderate 3 miles per hour (5-6 kph), corresponding to a steady, brisk walking pace of a person. If it swims too fast it will diminish its oxygen supplies and consequently shorten the dive duration. If it swims too slowly, it will not perform an effective search for prey items, nor will it be able to catch them. After some 2 to 3 minutes, the whale has reached a depth of 200 to 300 meters and complete darkness. At this depth, the whale starts to click. Approximately every second, the whale emits a powerful directional click from its huge nose, by far the largest sound generator in the animal kingdom. The clicks propagate away from the whale and bounce back from the bottom and intended prey items. By listening for and analyzing these echoes, the whale possibly creates an acoustic picture of its surroundings, allowing it to navigate and to locate, home in on and perhaps catch prey - the sperm whale is now echolocating. Sperm whales rely heavily on acoustic cues, as all other cues of the sperm whale are severely limited in the abyss. Surface light does not penetrate more than about 100 meters down the water column for which reason the only light at depth is originating from bioluminescent organisms. Olfaction or smell plays a major role in prey detection for a number of marine species, like sharks. This is not an option for sperm whales and other toothed whales as the olfactory part of the nervous system is completely reduced. Tactile cues may assist the sperm whale during close encounters with its prospective prey, but it cannot facilitate the detection of prey in the range of 100 meters or more as is the case in echolocation.

After a decent of 5 to 10 minutes, the whale reaches a depth of about 500 to 1000 meters. Sperm whales on average stay at this depth for approximately 25 minutes while searching for and ingesting prey. Their prey consists mainly of small to medium sized deepwater or bathypelagic squid, with an average length of three feet and weighing two pounds. Scientists do not know how sperm whales catch their prey. In order to maintain its body function, a medium sized sperm whale must catch some 500 to1000 prey items a day. When we consider that the energy return from the consumption of a single squid would not justify the energy expended by the whale in chasing and consuming it, we think that the sperm whale could target groups of prey.

After a period of approximately 40 minutes, the oxygen stores are diminishing, and it is time for the whale to head back to the surface where it inhales its first breath of air in 45 minutes. So although, the sperm whale is an air-breathing mammal, it spend by far most of its time submerged.

Log by Peter Teglberg Madsen & Genevieve Johnson

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