Watanuki Yutaka, Niizuma Yasuaki, Gabrielsen Geir Wing, Sato Katsufumi, Naito Yasuhiko
Laboratory of Animal Ecology, Graduate School of Agriculture, Hokkaido University, Kita-ku, Sapporo 060-8589, Japan.
Proc Biol Sci. 2003 Mar 7;270(1514):483-8. doi: 10.1098/rspb.2002.2252.
In order to increase locomotor efficiency, breath-holding divers are expected to adjust their forward thrusts in relation to changes of buoyancy with depth. Wing propulsion during deep diving by Brünnich's guillemots (Uria lomvia) was measured in the wild by high-speed (32 Hz) sampling of surge (tail-to-head) and heave (ventral-to-dorsal) accelerations with bird-borne data loggers. At the start of descent, the birds produced frequent surges (3.2 Hz) during both the upstroke and the downstroke against buoyancy to attain a mean speed of 1.2-1.8 m s(-1) that was close to the expected optimal swim speed. As they descended deeper, the birds decreased the frequency of surges to 2.4 Hz, relaying only on the downstroke. During their ascent, they stopped stroking at 18 m depth, after which the swim speed increased to 2.3 m s(-1), possibly because of increasing buoyancy as air volumes expanded. This smooth change of surge frequency was achieved while maintaining a constant stroke duration (0.4-0.5 s), presumably allowing efficient muscle contraction.
为了提高运动效率,预计屏气潜水者会根据深度变化引起的浮力变化来调整其向前推力。通过使用鸟类携带的数据记录器对起伏(从尾到头)和升沉(从腹到背)加速度进行高速(32赫兹)采样,在野外测量了厚嘴海鸦(乌燕鸥)深潜时的翅膀推进力。在下降开始时,鸟类在向上划水和向下划水时都频繁起伏(3.2赫兹)以对抗浮力,从而达到1.2 - 1.8米/秒的平均速度,这接近预期的最佳游泳速度。随着它们下潜得更深,鸟类将起伏频率降低到2.4赫兹,仅依靠向下划水。在它们上升过程中,它们在18米深度处停止划水,之后游泳速度增加到2.3米/秒,这可能是因为随着空气体积膨胀浮力增加。这种起伏频率的平稳变化是在保持恒定划水持续时间(0.4 - 0.5秒)的情况下实现的,大概这样能使肌肉有效收缩。