Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island
Marine mammals breeding in sympatry use resources differently depending on their time-activity budgets and prey distribution. We measured isotopic values and patterns of δ15N and δ13C in keratinous whiskers of satellite-tagged adult female Antarctic (Arctocephalus gazella) - and Subantarctic (Arctoc...
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ftunivpretoria:oai:repository.up.ac.za:2263/78596 2023-05-15T14:00:33+02:00 Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island Mukutyu, Itai De Bruyn, P.J. Nico Wege, Mia Lübcker, Nico 2021-04-10 http://hdl.handle.net/2263/78596 en eng University of Pretoria http://hdl.handle.net/2263/78596 * A2021 © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. UCTD Marine Mammals Stable Isotope ecology Zoology Dissertation 2021 ftunivpretoria 2022-05-31T13:27:17Z Marine mammals breeding in sympatry use resources differently depending on their time-activity budgets and prey distribution. We measured isotopic values and patterns of δ15N and δ13C in keratinous whiskers of satellite-tagged adult female Antarctic (Arctocephalus gazella) - and Subantarctic (Arctocephalus tropicalis) fur seals from three colonies at Marion Island in the Southern Indian Ocean. The three sympatric colonies were Mixed Pickle (HD_MP), Rockhopper Bay (LD_RhB), and Watertunnel (HD_WT). A comparison between two colonies of differing A. tropicalis densities will also be investigated. We investigated resource use in breeding mature females over varying time and spatial scales during summer and winter. The aim was to understand the variation in resource and habitat use at population and individual levels. The whiskers of A. gazella and A. tropicalis grow constantly at a rate of 0.16 ± 0.05 day-1 and 0.12 ± 0.05 day-1, respectively. To compare and relate behaviours, the stable isotope data and satellite tracks were grouped into winter and summer (pooled for 2010 - 2014). In summer, A. gazella from HD_WT had a larger isotopic niche width (0.85 ± 0.67‰2) compared to A. tropicalis from both HD_MP (0.18 ± 0.19‰2) and LD_RhB (0.21 ± 0.15‰2). However, the isotopic niche width of A. gazella reduced in size by more than half (0.40 ± 0.40‰2) during winter when the mature females were no longer constrained by the lactation mandate. The mean δ15N values in whiskers of both A. tropicalis and A. gazella in summer were similar (11.3 ± 0.4‰ and 11.0 ± 0.9‰, respectively). The A. gazella broadens its’ isotopic niche feeding at different trophic levels in summer (lactation period). We used a Repeatability index (R) to assess levels of intra- and inter-individual consistency. Repeatability indicated that the bigger isotopic niche width for A. gazella is attributed to high inter- and intra-individual variability in their resource use. The A. gazella individuals ranging closer to the colony consistently consumed myctophid ... Doctoral or Postdoctoral Thesis Antarc* Antarctic Arctocephalus gazella Marion Island University of Pretoria: UPSpace Antarctic Indian |
institution |
Open Polar |
collection |
University of Pretoria: UPSpace |
op_collection_id |
ftunivpretoria |
language |
English |
topic |
UCTD Marine Mammals Stable Isotope ecology Zoology |
spellingShingle |
UCTD Marine Mammals Stable Isotope ecology Zoology Mukutyu, Itai Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island |
topic_facet |
UCTD Marine Mammals Stable Isotope ecology Zoology |
description |
Marine mammals breeding in sympatry use resources differently depending on their time-activity budgets and prey distribution. We measured isotopic values and patterns of δ15N and δ13C in keratinous whiskers of satellite-tagged adult female Antarctic (Arctocephalus gazella) - and Subantarctic (Arctocephalus tropicalis) fur seals from three colonies at Marion Island in the Southern Indian Ocean. The three sympatric colonies were Mixed Pickle (HD_MP), Rockhopper Bay (LD_RhB), and Watertunnel (HD_WT). A comparison between two colonies of differing A. tropicalis densities will also be investigated. We investigated resource use in breeding mature females over varying time and spatial scales during summer and winter. The aim was to understand the variation in resource and habitat use at population and individual levels. The whiskers of A. gazella and A. tropicalis grow constantly at a rate of 0.16 ± 0.05 day-1 and 0.12 ± 0.05 day-1, respectively. To compare and relate behaviours, the stable isotope data and satellite tracks were grouped into winter and summer (pooled for 2010 - 2014). In summer, A. gazella from HD_WT had a larger isotopic niche width (0.85 ± 0.67‰2) compared to A. tropicalis from both HD_MP (0.18 ± 0.19‰2) and LD_RhB (0.21 ± 0.15‰2). However, the isotopic niche width of A. gazella reduced in size by more than half (0.40 ± 0.40‰2) during winter when the mature females were no longer constrained by the lactation mandate. The mean δ15N values in whiskers of both A. tropicalis and A. gazella in summer were similar (11.3 ± 0.4‰ and 11.0 ± 0.9‰, respectively). The A. gazella broadens its’ isotopic niche feeding at different trophic levels in summer (lactation period). We used a Repeatability index (R) to assess levels of intra- and inter-individual consistency. Repeatability indicated that the bigger isotopic niche width for A. gazella is attributed to high inter- and intra-individual variability in their resource use. The A. gazella individuals ranging closer to the colony consistently consumed myctophid ... |
author2 |
De Bruyn, P.J. Nico Wege, Mia Lübcker, Nico |
format |
Doctoral or Postdoctoral Thesis |
author |
Mukutyu, Itai |
author_facet |
Mukutyu, Itai |
author_sort |
Mukutyu, Itai |
title |
Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island |
title_short |
Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island |
title_full |
Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island |
title_fullStr |
Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island |
title_full_unstemmed |
Inter- and intraspecific variation in foraging ecology of sympatric fur seals Arctocephalus gazella and Arctocephalus tropicalis from Marion Island |
title_sort |
inter- and intraspecific variation in foraging ecology of sympatric fur seals arctocephalus gazella and arctocephalus tropicalis from marion island |
publisher |
University of Pretoria |
publishDate |
2021 |
url |
http://hdl.handle.net/2263/78596 |
geographic |
Antarctic Indian |
geographic_facet |
Antarctic Indian |
genre |
Antarc* Antarctic Arctocephalus gazella Marion Island |
genre_facet |
Antarc* Antarctic Arctocephalus gazella Marion Island |
op_relation |
http://hdl.handle.net/2263/78596 * A2021 |
op_rights |
© 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
_version_ |
1766269717295661056 |