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Keywords:

  • classification;
  • diving behavior;
  • Leptonychotes weddellii;
  • multivariate statistical tests;
  • satellite-linked time-depth recorder;
  • time-depth recorder;
  • Weddell seal

ABSTRACT

Most studies of pinniped diving behavior have manually grouped dives according to similarities in the depth, duration, and appearance of the dive profile. Dives of 15 adult female Weddell seals (Leptonychotes weddellii) were recorded with time-depth recorders and 39, 119 dives were classified manually and statistically (principal components analysis, discriminant function analysis, cluster analysis, and shape-fitting algorithms). Four dive types, common to all classification methods, and a fifth dive type, common to two of the methods, represented most of the observed diving behavior. However, a few variations of these dive types, specifically a flat-bottomed dive determined manually, may have also represented important behavior. Using a combination of these methods, all dives were classified into six dive types, Inspection of dive variables (mean maximum depth, mean duration, and frequency) over time for each dive type, as well as comparisons to previous studies of pinniped diving behavior, indicated different behaviors that the dive types may represent. Hypothesized functions for the dive types were pelagic foraging, benthic foraging, exploration, and traveling. The results indicate that there are strong similarities in diving behavior across various phocid species, that statistical analyses of diving behavior are useful in the analysis of a large data set, and that these analyses reduced human subjective bias in interpreting diving behavior.