Intrinsic and extrinsic forcing in life histories : patterns of growth and stable isotopes in male Antarctic fur seal teeth

Life-time records of the trophic sources of carbon, nitrogen and of growth rate can be generated from biogenic structures that show accretionary growth, including fish scales, whale baleen and the teeth of some animals. Records generated from individual teeth can also be combined to provide longer t...

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Bibliographic Details
Published in:Marine Ecology Progress Series
Main Authors: Hanson, Nora Nell, Wurster, Christopher Martin, Bird, Michael Ian, Reid, K, Boyd, Ian Lamont
Other Authors: University of St Andrews. School of Biology, University of St Andrews. Marine Alliance for Science & Technology Scotland, University of St Andrews. Sea Mammal Research Unit
Format: Article in Journal/Newspaper
Language:English
Published: 2013
Subjects:
Online Access:http://hdl.handle.net/10023/3969
https://doi.org/10.3354/meps08158
http://www.scopus.com/inward/record.url?scp=69849100913&partnerID=8YFLogxK
Description
Summary:Life-time records of the trophic sources of carbon, nitrogen and of growth rate can be generated from biogenic structures that show accretionary growth, including fish scales, whale baleen and the teeth of some animals. Records generated from individual teeth can also be combined to provide longer time series elucidating changes in environmental conditions encountered by a population. Both intrinsic (i.e. ontogenetic) and extrinsic (i.e. environmental) factors are important in modulating variation in growth and the apparent dietary sources of C and N. We used the canine teeth of a large marine predator, the male Antarctic fur seal Arctocephalus gazella from South Georgia, to investigate both intrinsic and extrinsic sources of variation. Substantial ontogenetic shifts occurred in both delta C-13 and delta N-15 values in individual teeth, indicating a change in the trophic sources of C and N as individual animals age. Over the 40 yr period from 1964 to 2005, and after statistical reduction of ontogenetic variation, we also detected long-term declines in delta C-13 and delta N-15 values, indicating that the population has become more dependent on energy from a lower trophic level. A concurrent decline in annular tooth growth may be a consequence of rapid population growth during this period. The time series of delta C-13 values was also inversely correlated with sea surface temperatures in the region, although isolating a causal relationship remains elusive. Our analyses suggest that both intrinsic and extrinsic sources of variation, and their interaction, must be considered from Such time series data; failure to do so could result in a biased interpretation. Publisher PDF Peer reviewed