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Age estimates based on aspartic acid racemization for bowhead whales (Balaena mysticetus) harvested in 1998–2000 and the relationship between racemization rate and body temperature

Authors

  • Cheryl Rosa,

    Corresponding authorCurrent affiliation:
    1. U. S. Arctic Research Commission, Anchorage, Alaska, U.S.A
    • University of Alaska Fairbanks, Institute of Arctic Biology, Department of Biology and Wildlife, Fairbanks, Alaska, U.S.A
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  • Judith Zeh,

    1. University of Washington, Department of Statistics, Seattle, Washington, U.S.A
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  • J. Craig George,

    1. Department of Wildlife Management, North Slope Borough, Barrow, Alaska, U.S.A
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  • Oliver Botta,

    1. Scripps Institution of Oceanography, UCSD, San Diego, California, U.S.A
    Current affiliation:
    1. International Space Science Institute, Bern, Switzerland
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  • Melanie Zauscher,

    1. Scripps Institution of Oceanography, UCSD, San Diego, California, U.S.A
    Current affiliation:
    1. Department of Mechanical & Aerospace Engineering, University of California, San Diego, La Jolla, California, U.S.A
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  • Jeffrey Bada,

    1. Scripps Institution of Oceanography, UCSD, San Diego, California, U.S.A
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  • Todd M. O'Hara

    1. University of Alaska Fairbanks, Institute of Arctic Biology, Department of Biology and Wildlife, Fairbanks, Alaska, U.S.A
    2. Department of Wildlife Management, North Slope Borough, Barrow, Alaska, U.S.A
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Corresponding author (e-mail: crosa@arctic.gov).

Abstract

Fifty-two eyes were collected and analyzed to estimate ages of 42 bowhead whales using the aspartic acid racemization aging technique. Between-eye and within-eye variance components for the ratio of the D and L optical isomers (D/L ratio) were estimated via analysis of variance using multiple measurements from nine whales with both eyes sampled and analyzed. For whales with more than one (D/L)act value, an inverse variance weighted average of the values was used as (D/L)act for the whale. Racemization rate (kAsp) and D/L ratio at birth (D/L)0 were estimated using (D/L)act from 27 bowhead whales with age estimates based on baleen or ovarian corpora data and two term fetuses. The estimates were kAsp = 0.977 × 10−3/yr and (D/L)0 = 0.0250. The nonlinear least squares analysis that produced these estimates also estimated female age at sexual maturity as ASM = 25.86 yr. SE(age) was estimated via a bootstrap that took into account the SE of (D/L)act and the variances and covariance of kAsp and (D/L)0. One male exceeded 100 yr of age; the oldest female was 88. A strong linear relationship between kAsp and body temperature was estimated by combining bowhead data with independent data from studies of humans and fin whales. Using this relationship, we estimated kAsp and ASM for North Atlantic minke whales.

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