Remote monitoring of resource allocation to growth vs energy storage in space and time by sexually dimorphic elephant seals foraging at sea

尽管最近对大型海洋脊椎动物在海上的运动和行为的研究取得了相当大的进展，但对觅食活动和相关的身体状况变化，如总质量和脂肪含量的持续测量仍然难以捉摸。这些信息对于了解觅食生态学与重要海洋觅食者种群调节之间的联系、在空间和时间上更准确地确定具有特殊管理意义的区域以及查明全球气候变化的食物链影响至关重要。新开发的技术已经被用于档案数据记录器，以对动物的游泳行为进行高分辨率测量，例如识别动物何时滑行。动物的形态和身体状况(密度和总质量)决定了在滑行过程中影响动物运动的阻力和浮力。因此，通过仔细分析海豹在滑行过程中是如何减速的，我们可以估计动物密度(即身体组成)和海豹的质量。我们将在5-6岁的雄性和雌性象海豹身上安装传感器，以跟踪它们在南大洋8个月的觅食迁徙过程中身体成分和质量的变化。我们将仔细测量海豹在迁徙前贴上标签时的质量和密度，以及当海豹返回繁殖地时标签被找回时的质量和密度。这个年龄的象海豹预计会根据性别使用不同的组织分配策略，雄性海豹从瘦肉组织的增长中受益最大，因为它的身体更大，雌性海豹则受益于增加的能量储存，以便通过哺乳转移给后代。然而，在之前的最后几个月里，怀孕的女性面临着巨大的压力，必须为快速增长的胎儿提供精瘦的组织。有了这种新的方法，我们将能够确定海豹对其体内不同组织做出这些关键贡献的时间、时间和位置。由于这种顶级捕食者的健康依赖于食物网，这项技术将允许我们利用它们来研究它们所依赖的生态系统健康的变化。一旦开发出来，所开发的仪器和方法将适用于世界各地的其他海豹和海洋脊椎动物物种。为了实现这一目标，我们将利用研究人员和合作者的现有技术和技能，开发一种具有双重功能的仪器：1)测量和存档大量数据，以高分辨率分析在整个海上长期迁徙过程中身体成分和行为的变化，以及2.)对标签上的数据进行有意义的压缩和处理，以便近实时地通过Argos卫星系统进行中继。除了这项建议的具体科学目标外，这些仪器和分析技术的发展有可能极大地增加我们对许多海洋脊椎动物的觅食生态和自由活动的能量的了解，这些脊椎动物包括鳍脚类、海龟、鲸类和鲨鱼。

Despite considerable recent progress in studies of movements and behaviour of large marine vertebrates at sea, continuous measures of foraging activity and associated changes in body condition such as total mass and fat content have remained elusive. Such information is essential for understanding the links between foraging ecology and population regulation of important marine foragers, for identifying areas of special management significance more accurately in space and time, and for identifying food chain effects of global climate change. Newly developed technologies have been used in archival data loggers to make high-resolution measurements of animal swimming behaviour, such as identifying when an animal is gliding. Animal morphology and body condition (density and total mass) determine the drag and buoyancy forces affecting animal movement during a glide. Therefore, by analysing closely how seals slow down during glides, we can estimate both animal density (i.e. body composition) and mass of the seal. We will deploy sensors on 5-6 year old male and female elephant seals to track changes in body composition and mass during the 8-month feeding migration they make in the Southern Ocean. We will carefully measure the mass and density of the seals when the tag is attached prior to the migration, and again when the tags are recovered when the seals return to the breeding grounds. Elephant seals of this age are expected to use different tissue allocation strategies depending on sex, with males benefiting most from lean-tissue growth for increased body size and females benefiting from increased energy stores for transfer to their offspring through lactation. However, during the final few months before, a pregnant female is under strong pressure to provide lean tissue to the rapidly growing foetus. With this new approach, we will be able to identify the timing when, and location in the Southern ocean where, seals make these critical contributions to different tissues within their body. As the health of such top predators depends on the food web, this technique will allow us to use them to study variations in the health of the ecosystem on which they depend. Once developed, the instrumentation and methodologies developed will be applicable to other seal and marine vertebrate species, across the world's oceans. To achieve this goal, we will build on existing technologies and skills of the researchers and collaborators to develop an instrument with dual functions: 1.) measuring and archiving large quantities of data for high-resolution analyses of changes in body composition and behavior throughout long at-sea migrations, and 2.) meaningfully compressing and processing data on-board the tag for relay via the ARGOS satellite system in near real-time. Apart from the specific scientific objectives of this proposal, the development of these instruments and analysis techniques has the potential to significantly add to our understanding of the foraging ecology and free-ranging energetics of many marine vertebrates, such as pinnipeds, turtles, cetaceans and sharks.