Beluga Whales :: essays research papers

A. Swimming. 1. In general, beluga whales are slow swimmers. They commonly swim about 3 to 9 kph (1.9-5.6 mph). They are, however, capable of sustaining a maximum speed of 22 kph (13.6 mph) for as long as 15 minutes (Nowak, 1991; Ridgway and Harrison, 1981). 2. Belugas can swim forward and backward (Nowak, 1991). 3. Beluga whales often swim at depths barely covering their bodies (Ridgway and Harrison, 1981). B. Diving. 1. Beluga whales typically don't dive very deep, usually to about 20 m (66 ft.). Belugas are not generally thought of as deep-diving marine mammals, but they are capable of diving to extreme depths. Under experimental conditions a trained beluga whale repeatedly dove to 400 m (1,312 ft.) with ease, and even dove to a depth of 647 m (2,123 ft.) (Nowak, 1991; Ridgway et. al., 1984). 2. A typical dive usually lasts three to five minutes, but belugas can stay submerged for as long as 15 minutes (Nowak, 1991; Ridgway and Harrison, 1981). 3. In estuaries the usual diving sequence lasts about two minutes; the sequence consists of five to six shallow dives followed by a one-minute-long deeper dive (Ridgway and Harrison, 1981). 4. All marine mammals have physiological adaptations for diving. These adaptations enable a beluga whale to conserve oxygen while it's under water. a. Beluga whales, like other marine mammals, have a slower heart rate while diving. A beluga whale's heart rate slows from about 100 to about 12 to 20 beats per minute during a dive (Ridgway, 1972). b. When diving, blood is shunted away from tissues tolerant of low oxygen levels toward the heart, lungs, and brain, where oxygen is needed. c. Beluga whales retain more oxygen in their blood than most mammals do. A beluga whale's blood volume percentage (5.5%) is higher than a land mammal's, and similar to a Weddell seal's (a deep-diving marine mammal). One study found a female beluga to have 16.5 l (17.4 qt.) of oxygen in her blood (Ridgway et. al., 1984). d. The muscle of beluga whales has a high content of the oxygen-binding protein myoglobin. Myoglobin stores oxygen and helps prevent muscle oxygen deficiency. C. Respiration. 1. A beluga whale breathes through a single blowhole, a modified nasal opening. a. The beluga whale holds its breath while under water. b. It opens its blowhole and begins to exhale just before reaching the surface of the water. c.