DOI: 10.5061/dryad.269qr
title: Data from: Reproductive success is energetically linked to foraging efficiency in Antarctic fur seals

description: The 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.
description: AFS 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