Pup Vibrissae Stable Isotopes Reveal Geographic Differences in Adult Female Southern Sea Lion Habitat Use during Gestation.
Individuals within populations often differ substantially in habitat use, the ecological consequences of which can be far reaching. Stable isotope analysis provides a convenient and often cost effective means of indirectly assessing the habitat use of individuals that can yield valuable insights into the spatiotemporal distribution of foraging specialisations within a population. Here we use the stable isotope ratios of southern sea lion (Otaria flavescens) pup vibrissae at the Falkland Islands, in the South Atlantic, as a proxy for adult female habitat use during gestation. A previous study found that adult females from one breeding colony (Big Shag Island) foraged in two discrete habitats, inshore (coastal) or offshore (outer Patagonian Shelf). However, as this species breeds at over 70 sites around the Falkland Islands, it is unclear if this pattern is representative of the Falkland Islands as a whole. In order to characterize habitat use, we therefore assayed carbon (δ13C) and nitrogen (δ15N) ratios from 65 southern sea lion pup vibrissae, sampled across 19 breeding colonies at the Falkland Islands. Model-based clustering of pup isotope ratios identified three distinct clusters, representing adult females that foraged inshore, offshore, and a cluster best described as intermediate. A significant difference was found in the use of inshore and offshore habitats between West and East Falkland and between the two colonies with the largest sample sizes, both of which are located in East Falkland. However, habitat use was unrelated to the proximity of breeding colonies to the Patagonian Shelf, a region associated with enhanced biological productivity. Our study thus points towards other factors, such as local oceanography and its influence on resource distribution, playing a prominent role in inshore and offshore habitat use.
South Atlantic Environmental Research Institute, Stanley, FIQQ1ZZ, Falkland Islands.|Falklands Conservation, Stanley, FIQQ1ZZ, Falkland Islands.|Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
Alastair M M
AM
Baylis
Department of Animal Behaviour, Bielefeld University, Bielefeld, Germany.|Department of Animal Ecology, University of Potsdam, Potsdam, Germany.
Gabriele J
GJ
Kowalski
Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315, Berlin, Germany.
Christian C
CC
Voigt
Department of Fisheries and Wildlife, Oregon State University, Hatfield Marine Science Center, Newport, Oregon, 97365, United States of America.
Rachael A
RA
Orben
Department of Animal Behaviour, Bielefeld University, Bielefeld, Germany.
Fritz
F
Trillmich
British Antarctic Survey NERC, High Cross, Madingley Road, Cambridge, CB3 0ET, United Kingdom.
Iain J
IJ
Staniland
Department of Animal Behaviour, Bielefeld University, Bielefeld, Germany.
Joseph I
JI
Hoffman
D000818:Animals; D001947:Breeding; D002247:Carbon Isotopes / Q000378:metabolism; D016000:Cluster Analysis; D003247:Conservation of Natural Resources / Q000379:methods; D017753:Ecosystem; D019432:Falkland Islands; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D005843:Geography; D062312:Islands; D008297:Male; D008962:Models, Theoretical; D009587:Nitrogen Isotopes / Q000378:metabolism; D011157:Population Dynamics; D046070:Sea Lions / Q000378:metabolism / Q000502:physiology*; D014738:Vibrissae / Q000378:metabolism*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes