Stable Isotope Values in South American Fur Seal Pup Whiskers as Proxies of Year-round Maternal Foraging Ecology
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ORIGINAL PAPER
Stable Isotope Values in South American Fur Seal Pup Whiskers as Proxies of Year‑round Maternal Foraging Ecology Kayleigh A. Jones1,2 · Alastair. M. M. Baylis3,4 · Rachael A. Orben5 · Norman Ratcliffe1 · Stephen C. Votier2 · Jason Newton6 · Iain J. Staniland1 Received: 9 April 2020 / Accepted: 28 August 2020 / Published online: 29 September 2020 © The Author(s) 2020
Abstract Natural selection should favour strategies that maximise reproductive success. Females may use different resources during progressive stages of reproduction according to energetic demands, behavioural constraints and prey availability. We used South American fur seal, Arctocephalus australis australis, pup whisker isotope values as proxies for maternal diet and habitat use to determine how resource use (1) changes throughout pup development from in utero growth to mid-end of lactation and (2) how it differs among individuals. The longest whisker was cut from 5 male and 5 female fur seal pups (of approximately 8 months of age) at Bird Island, Falkland Islands, in 2018, and δ15N values and δ13C values were analysed every 5 mm along the length of each whisker. Patterns in δ13C values indicated that mothers used different habitats during the annual cycle, likely coinciding with seasonal shifts in prey availability or distribution. The individual specialisation index based on δ13C values was 0.34, indicating that adult females used different habitats, which could reduce intra-specific competition and ultimately enhance pup growth and survival. An increase in δ15N values occurred along every pup whisker from pup birth to mid-end of lactation, which likely reflected trophic enrichment related to suckling and fasting by pups, overriding the maternal isotopic signature. Pup whisker stable isotopes are useful proxies of maternal foraging ecology. However, physiological processes complicate interpretations by altering δ15N values. Interpreting these values therefore requires additional knowledge of the species’ ecology and physiology.
Introduction Responsible Editor: C. Harrod. Reviewed by undisclosed experts. * Kayleigh A. Jones [email protected] 1
British Antarctic Survey, High Cross, Madingley Rd, Cambridge CB3 0ET, UK
2
University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, UK
3
South Atlantic Environmental Research Institute, Stanley Cottage, PO Box 609, Stanley FIQQ 1ZZ, Falkland Islands
4
Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia
5
Department of Fisheries and Wildlife, Oregon State University, Hatfield Marine Science Center, 2030 SE Marine Science Dr, Newport, OR 97365, USA
6
National Environmental Isotope Facility, Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride G75 0QF, UK
In mammals, gestation and lactation have different energetic requirements that influence maternal resource use (Gittleman and Thompson 1988). During gestation, female mammals must grow and maintain foetal, uterine, placental and mammary
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