Data from: Reproductive success is energetically linked to foraging efficiency in Antarctic fur seals

AbstractThe efficiency with which individuals extract energy from their environment defines their survival and reproductive success, and thus their selective contribution to the population. Individuals that forage more efficiently (i.e., when energy gained exceeds energy expended) are likely to be more successful at raising viable offspring than individuals that forage less efficiently. Our goal was to test this prediction in large long-lived mammals under free-ranging conditions. To do so, we equipped 20 lactating Antarctic fur seals (Arctocephalus gazella) breeding on the Kerguelen Island in the Southern Ocean with tags that recorded GPS locations, depth and tri-axial acceleration to determine at-sea behaviours and detailed time-activity budgets during their foraging trips. We also simultaneously measured energy spent at sea using the doubly-labeled water (DLW) method, and estimated the energy acquired while foraging from 1) type and energy content of prey species present in scat remains, and 2) numbers of prey capture attempts determined from head acceleration. Finally, we followed the growth of 36 pups from birth until weaning (of which 20 were the offspring of our 20 tracked mothers), and used the relative differences in body mass of pups at weaning as an index of first year survival and thus the reproductive success of their mothers. Our results show that females with greater foraging efficiencies produced relatively bigger pups at weaning. These mothers achieved greater foraging efficiency by extracting more energy per minute of diving rather than by reducing energy expenditure. This strategy also resulted in the females spending less time diving and less time overall at sea, which allowed them to deliver higher quality milk to their pups, or allowed their pups to suckle more frequently, or both. The linkage we demonstrate between reproductive success and the quality of individuals as foragers provides an individual-based quantitative framework to investigate how changes in the availability and accessibility of prey can affect fitness of animals., Usage notesAFS females dataData collected on Antarctic fur seal colony on Kerguelen Island during the breeding season in 2012. Only females were selected. capt = capture date, massrecap = mass at recapture, lengthrecap = length at recapture, girthrecap = girth at recapture, departure= date of departure at sea, return = date of return to colony, minatsea = foraging trip duration in min, DEEkJd = Daily energy expenditure at sea in kJ/d, pup = ID of the female associated pup, Psex = sex of the pup associated with the tracked female, timeonland = time females spent on land between capture and departure at sea and between return and recapture, PCA = number of Prey Capture Attempts during foraging trip,Scat analyses dataScats were collected on the fur seal colony and were analysed for hard part remains. KFS1201 to KFS1214 indicate number of individual scats.AFSDietScats2012.xlsxAntarctic fur seal Pup dataMorphometric data collected on Antarctic fur seal pups on Kerguelen island during the breeding period in 2012. Tag# = ID of individual pups, Date = date of morphometric measurements (first date is birth date), mass = mass in kg, length = length in cm, girth = axillary girth in cm, sex = sex of pup.Pup data T. Jeanniard du Dot.xlsxTelemetry data of female Antarctic fur seals at sea.Telemetry data was collected using MK10 tags from Wildlife Computers for one foraging trip of breeding Antarctic fur seal females on Kerguelen during the breeding season 2012. Females are identified with a individual number from 21 to 40. File named Locations provide the latitude and longitude of GPS points collected. File named Archive provide dive depth (in m) of females at sea as well as water temperature (in C) and light levels in water at sampling rate of 1Hz during the foraging trip.Telemetry data.zip

摘要 个体从环境中获取能量的效率决定了其生存与繁殖成功率，进而决定了其对种群的选择贡献。觅食效率更高的个体（即获取能量大于消耗能量的个体），相较于觅食效率较低的个体，更有可能成功抚育出可存活的后代。本研究旨在在野外自由活动的大型长寿哺乳动物中验证这一预测。为此，我们为南大洋凯尔盖朗岛上繁殖的20头泌乳南极海狗（Arctocephalus gazella）佩戴了记录GPS位置、水深及三轴加速度的标签，以确定其海上行为及觅食旅程中的详细时间-活动预算。我们同时采用双标记水（doubly-labeled water, DLW）法测量其海上消耗的能量，并通过以下两种方式估算觅食过程中获取的能量：1）粪便残骸中猎物物种的类型与能量含量；2）由头部加速度识别的猎物捕获尝试次数。最后，我们跟踪了36头幼崽从出生到断奶的生长过程（其中20头为本次研究中20头被跟踪母海狗的后代），并以幼崽断奶时的体重相对差异作为其第一年存活率的指标，进而反映母海狗的繁殖成功率。研究结果显示，觅食效率更高的母海狗在幼崽断奶时能抚育出体型相对更大的幼崽。这类母海狗通过提升每分钟潜水的能量获取量，而非降低能量消耗，来获得更高的觅食效率。该策略同时使母海狗的潜水时长与总海上停留时长缩短，使其能够为幼崽提供更高质量的乳汁，或让幼崽获得更频繁的哺乳机会，或两者兼具。本研究揭示了繁殖成功率与个体觅食能力之间的关联，为探究猎物可获得性与可获取性的变化如何影响动物的适合度提供了基于个体的定量框架。

使用说明

## 南极海狗母海狗数据集
2012年繁殖季在凯尔盖朗岛南极海狗繁殖群落采集的数据，仅纳入母海狗个体。其中：
capt为捕获日期；massrecap为再次捕获时的体重；lengthrecap为再次捕获时的体长；girthrecap为再次捕获时的围度；departure为出海出发日期；return为返回群落日期；minatsea为觅食旅程时长（单位：分钟）；DEEkJd为海上每日能量消耗（单位：千焦/天）；pup为对应幼崽的编号；Psex为被跟踪母海狗所育儿崽的性别；timeonland为母海狗在捕获至出海出发，以及返回至再次捕获期间的陆栖时长；PCA为觅食旅程中的猎物捕获尝试次数。

## 粪便分析数据集
在海狗繁殖群落收集粪便样本，对其硬质残骸进行分析。KFS1201至KFS1214代表单份粪便样本的编号。数据集文件为AFSDietScats2012.xlsx。

## 南极海狗幼崽数据集
2012年繁殖季在凯尔盖朗岛采集的南极海狗幼崽形态测量数据。其中：
Tag#为幼崽个体编号；Date为形态测量日期（首条记录日期为出生日期）；mass为体重（单位：千克）；length为体长（单位：厘米）；girth为腋围（单位：厘米）；sex为幼崽性别。数据集文件为Pup data T. Jeanniard du Dot.xlsx。

## 南极海狗母海狗海上遥测数据集
2012年繁殖季，在凯尔盖朗岛对繁殖期母南极海狗的一次觅食旅程进行遥测数据采集，所用设备为Wildlife Computers公司的MK10标签。母海狗以21至40的个体编号标识。Locations文件包含采集到的GPS点经纬度信息；Archive文件包含觅食旅程中以1Hz采样率记录的母海狗海上潜水深度（单位：米）、海水温度（单位：摄氏度）及水中光照强度数据。数据集压缩包为Telemetry data.zip。