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Keywords:

  • Monachus schauinslandi;
  • monk seal;
  • Northwestern Hawaiian Islands;
  • reproduction;
  • fecundity;
  • reproductive senescence;
  • population modeling;
  • sensitivity analysis

Abstract

We evaluated reproductive patterns of the Hawaiian monk seal (Monachus schauinslandi) using a combination of fitted age-specific reproductive curves and analysis of reproductive patterns of individual females. We review the difficulties inherent in the acquisition and modeling of reproductive data with emphasis on the significance of reproductive senescence to populations with dissimilar age/sex compositions. Validation of the fitted reproductive parameters was accomplished by Monte Carlo sampling of parameter distributions to compare the expected number of pups with the observed production. Although the fitted reproductive functions appear to provide an acceptable fit to the raw reproductive data, we found that the fitted curves did a poor job of predicting the actual pup production in individual years because of high variability among years. To further verify, and elaborate on, the patterns in the pooled (multi-seal, and multi-year) rates, we examined attributes of the reproductive performance of individual seals. The attributes included age of primiparity, reproductive rates computed over several age ranges, and the relationship between reproductive performance and seal longevity. Analysis of individual seal patterns reinforced the conclusion that reproductive senescence is operative in monk seal populations.