Get access

The buoyancy of the integument of Atlantic bottlenose dolphins (Tursiops truncatus): Effects of growth, reproduction, and nutritional state

Authors

  • Robin C. Dunkin,

    1. Department of Ecology and Evolutionary Biology,
      University of California at Santa Cruz,
      100 Shaffer Road,
      Santa Cruz, California 95060, U.S.A.
      and
      Department of Biology and Marine Biology,
      University of North Carolina Wilmington,
      601 S. College Road,
      Wilmington, North Carolina 28403, U.S.A.
      E-mail: dunkin@biology.ucsc.edu
    Search for more papers by this author
  • William A. McLellan,

    1. Department of Biology and Marine Biology,
      University of North Carolina Wilmington,
      601 S. College Road,
      Wilmington, North Carolina 28403, U.S.A.
    Search for more papers by this author
  • James E. Blum,

    1. Department of Mathematics and Statistics,
      University of North Carolina Wilmington,
      601 S. College Road,
      Wilmington, North Carolina 28403, U.S.A.
    Search for more papers by this author
  • D. Ann Pabst

    1. Department of Biology and Marine Biology,
      University of North Carolina Wilmington,
      601 S. College Road,
      Wilmington, North Carolina 28403, U.S.A.
    Search for more papers by this author

Abstract

In Atlantic bottlenose dolphins (Tursiops truncatus) the thickness and lipid content of blubber (the integument's specialized hypodermis) varies across ontogeny and with reproductive and nutritional state. Because the integument comprises up to 25% of total body mass in this species, ontogenetic changes in its lipid content may influence whole body buoyancy. The density and volume of the integument were measured and its buoyancy calculated across an ontogenetic series of dolphins and in pregnant and emaciated adults (total n= 45). Regional differences between the metabolically labile trunk integument and the structural tailstock integument were also investigated. Mean densities of both trunk and tailstock integument were similar across life history categories (trunk = 1,040.7 ± 14.1 kg/m3; tailstock = 1,077.1 ± 21.2 kg/m3) and were statistically similar to the density of seawater (1,026 kg/m3). The mean buoyant force of integument from the trunk (−1.01 ± 1.74 N) and tailstock (−0.30 ± 0.21 N) did not vary significantly across ontogeny. In contrast, pregnancy and emaciation did influence the integument's buoyancy, which ranged between 9 N and −45 N in these categories. Although neutral during growth, the integument's contribution to whole body buoyancy can be influenced by an individual's reproductive and nutritional status.

Ancillary