Marine Conservation, Research, & Observations

OUT OF THE DEPTHS: MYSTERIES OF OUR OFFSHORE DEEP-DIVING WHALES

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Photo credit: Cape May Whale Watch & Research Center Database

Far out in the Atlantic lurk strange creatures considered to be the deepest diving of all mammals. These record setting animals are Cuvier’s beaked whales (Ziphius cavirostris). Normally found far from shore, the Research Center has encountered and photographed individuals of this species during pelagic birding and whale watching trips.

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Photo credit: Cape May Whale Watch & Research Center Database

The beaked whale family consists of at least 20 different species of small to mid-sized whales. All have a prominent beak-like snout similar in form to that of a dolphin. Cuvier’s beaked whale is the most widespread of this group, and may be encountered in most seas and oceans throughout the world. Individuals may reach a maximum length of 23 ft. and weigh up to 6,800 lbs., which is not exceptionally large for a whale. They generally present a low profile at the surface and produce a short spout about 3 ft. high. Sometimes sighted alone, they are also sighted in groups of 2-12 individuals.

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Photo credit: Cape May Whale Watch & Research Center Database

Although beaked whales are odontocetes, or toothed whales, the teeth are often minimal and may have primary functions not even related to feeding. Cuvier’s beaked whales have two teeth which erupt at the tip of the lower jaw in males only. Males use their teeth in competitive fighting for females, which results in dramatic scarring patterns stretching the length of the whale as shown here. These whales feed primarily on squid, and rely upon suction rather than impressive rows of teeth to capture their prey.

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Photo credit: Cape May Whale Watch & Research Center Database

To find suitable prey items, this whale possesses some of the most remarkable diving abilities of any mammal. Individuals have been tracked to depths of 9,816 ft. and can remain submerged for up to 138 minutes! Because they prefer the squid species found at such depths, Cuvier’s beaked whales are almost never sighted in shallow waters. Sighting them may require a trip of nearly 100 miles offshore to reach the deep waters they normally frequent.

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Photo credit: Cape May Whale Watch & Research Center Database

There are other whale species which descend to great depths in order to feed. The most physically impressive of all deep diving whales is the sperm whale (Physeter macrocephalus), which is the largest of all toothed whales. Males may measure at least 52 ft in length and weigh over 90,000 lbs! This animal, the largest toothed predator on the planet, will sometimes attack the legendary giant squid (Architeuthis dux). They dive more than 3,000 ft deep and hold their breath for more than an hour to locate their prey. Sperm whales and Cuvier’s beaked whales are both beasts of the open ocean. With the exception of a few very special regions around the world, these species are never seen near the shore unless sick or injured.

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Photo Credit: Michael A. Denk

How can the Cuvier’s beaked whale and sperm whale deal with the immense pressure at great depths? Answers to this question lie within the peculiar anatomy of these animals. Rather than try to withstand the crushing pressure of water, a whale’s body is structured to partially collapse at depth . Notice how the sperm whale ribcage above has only a few of the ribs connected by a middle bone (sternum) in the front chest region. Most of the ribs are free to hinge backwards towards the tail, and the internal organs are layered so that they are not damaged by the compression. Therefore, a whale’s ribcage will not crush, but merely flex backwards under the massive hug of pressure given by the ocean.

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Photo credit: Cape May Whale Watch & Research Center Database

But how can a whale survive without breathing for such a long period of time? Firstly, whales have exceptionally efficient lungs. When they breathe, 90% of the air in the lungs is exchanged, as opposed to 15% in land dwelling mammals such as a human. This allows an immense amount of oxygen to be gained with every breath. In addition to this, the oxygen is stored in the body very differently than in a human. whales store proportionately much more oxygen in muscular tissues, which act as a set of reservoirs. In humans, 57% of the total body oxygen store is in the blood, while only 15% is in the muscles. In a whale, 30% is in the blood and 48% is in the muscles. Whale muscles and internal organs are rich in myoglobin, a special protein which helps to secure the oxygen in these areas. In essence, the muscles function as a series of onboard oxygen tanks.

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Photo credit: Cape May Whale Watch & Research Center Database

Since the muscular system well as other areas of the body have their own stored supply, the remaining oxygen in the blood can be used very economically. It is only directed where it is needed the most, such as the brain or spinal cord, and the heart rate may slow dramatically. Reducing function of unnecessary organs is also very important for oxygen efficiency. Whales and other marine mammals such as seals can shut down the function of the liver, kidney, and digestive tract to further conserve energy and oxygen. Upon surfacing after a dive, the whale will not only gain new oxygen but also void the waste products accumulated from body processes that may need to work without oxygen (anaerobically) during the dive. This is why many species may be observed resting and spouting frequently at the surface for a long time before beginning any more strenuous activity.

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Photo credit: Cape May Whale Watch & Research Center Database

Studying deep diving whales such as Cuvier’s beaked whale and the sperm whale is often very difficult due to the long diving times and elusive behaviors of these animals at the surface. Nonetheless, there is a great thrill to observing these animals, which regularly travel to some of the darkest and least known regions of our world. As Herman Melville wrote in Moby Dick “Of all divers, thou hast dived the deepest. That head upon which the sun now gleams, has moved among this world’s foundations.” Such is the mysterious wonder of deep diving whales!

By Michael Denk, Intern at Cape May Whale Watch and Research Center

http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/beakedwhale_cuviers.htm

http://news.nationalgeographic.com/news/2014/03/140326-cuvier-beaked-whale-record-dive-depth-ocean-animal-science/

http://acsonline.org/fact-sheets/cuviers-beaked-whale/

http://www.nmfs.noaa.gov/pr/health/noise/docs/macleod_behavior.pdf

http://acsonline.org/fact-sheets/sperm-whale/

http://uncw.edu/mmsp/documents/Rommel-2006BeakedWhaleMorph.pdf

http://www.bbc.com/earth/story/20150115-extreme-divers-defy-explanation

Fontaine, Pierre-Henry Whales and Seals: Biology and Ecology, Schiffer Publishing; 0003- edition)

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