Why do macaroni penguins choose shallow body angles that result in longer descent and ascent durations?
Why do macaroni penguins choose shallow body angles that result in longer descent and ascent durations?
复制标题
DOI：
10.1242/jeb.01265
复制
发表时间：
2004-11-01
影响因子：
2.8
通讯作者：
Naito, Y
中科院分区：
文献类型：
--
作者：
Sato, K;Charrassin, JB;Naito, Y
一般认为，呼吸空气的水生动物总是选择最短的路线，以最大限度地减少从水面到觅食深度之间的过境时间，以便最大限度地增加觅食时间的比例。然而，经验数据表明，一些潜水动物的身体角度在下降和上升过程中很少是垂直的。为什么他们选择较浅的身体角度，这会导致更长的下降和上升持续时间？为了研究这个问题，我们在8只雌性通心粉企鹅身上安装了加速度数据记录器，这些企鹅在科尔盖伦群岛(48度45‘-50度00’S，68度45‘-70度58’E；南印度洋)繁殖，记录深度、二维加速度(划水周期频率和身体角度)和温度。我们调查了它们如何控制身体角度和分配浸泡时间。带仪表器的雌鸟进行了多次俯冲(N=6952)，每只鸟的平均俯冲深度从24.5+/-28.5米到56.4+/-75.1米。对于给定的潜水深度，平均下降和上升角度有很大的变化，这反过来又导致下降和上升持续时间的巨大变化。体角与潜水最低阶段所花费的时间显著相关。在底部停留较长时间的鸟类在上升和随后的下降过程中身体角度都很陡峭。相比之下，他们在有较短的或没有底部阶段后，采用了浅体角。我们的结果表明，通心粉企鹅在遇到一个好的猎物补丁后，会在底部停留更长时间，然后以陡峭的身体角度移动到表面。如果没有遇到猎物，它们会停止潜水，不停留在底部，在接下来的潜水中以浅体角上升，以浅体角下降。较浅的身体角度可以增加俯冲过程中的水平距离，有助于在接下来的潜水中进入更有利可图的区域。特别是在上升过程中，通心粉企鹅不再敲打它们的鳍状肢。浮力滑行的企鹅在到达水面之前可以用最小的划水力气水平移动。
It is generally assumed that air-breathing aquatic animals always choose the shortest route to minimize duration for transit between the surface and foraging depth in order to maximize the proportion of time spent foraging. However, empirical data indicate that the body angles of some diving animals are rarely vertical during descent and ascent. Why do they choose shallower body angles that result in longer descent and ascent durations? To investigate this question, we attached acceleration data loggers to eight female macaroni penguins, breeding on the Kerguelen Islands (48degrees45'-50degrees00' S, 68degrees45'-70degrees58' E; South Indian Ocean), to record depth, two-dimensional acceleration (stroke cycle frequency and body angle) and temperature. We investigated how they controlled body angle and allocated their submerged time. The instrumented females performed multiple dives (N=6952) with a mean dive depth for each bird ranging from 24.5 +/- 28.5 m to 56.4 +/- 75.1 m. Mean body angles during descent and ascent were not vertical. There was large variation in mean descent and ascent angles for a given dive depth, which, in turn, caused large variation in descent and ascent duration. Body angles were significantly correlated with time spent at the bottomphase of the dive. Birds that spent long periods at the bottom exhibited steep body angles during ascent and subsequent descent. By contrast, they adopted shallow body angles after they had short or no bottom phases. Our results suggest that macaroni penguins stay at the bottom longer after encountering a good prey patch and then travel to the surface at steep body angles. If they do not encounter prey, they discontinue the dive, without staying at the bottom, ascend at shallow body angles and descend at shallow body angles in a subsequent dive. A shallow body angle can increase the horizontal distance covered during a dive, contributing to the move into a more profitable area in the following dive. During the ascent, in particular, macaroni penguins stopped beating their flippers. The buoyantly gliding penguins can move horizontally with minimum stroking effort before reaching the surface.