Ranging and association patterns of paired and unpaired adult male Atlantic bottlenose dolphins, Tursiops truncatus, in Sarasota, Florida, provide no evidence for alternative male strategies

Authors:
  • EOEdward C.G Owen
    Edward C.G Owen
  • RWRandall S Wells
    Randall S Wells
  • SHSue Hofmann
    Sue Hofmann
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Abstract
Previous studies of Atlantic bottlenose dolphin, Tursiops truncatus, social structure near Sarasota, Florida, revealed two distinct patterns of ranging and association among paired and unpaired adult males. We evaluated these patterns using a longer-term dataset to examine whether they represent alternative strategies. Males were categorized as paired or unpaired based on coefficients of association using survey data collected year-round from 1993 to 2000. Longitudinal data also allowed for determination of lifetime pair-bond status, which enabled analysis of the occurrence of alternative strategies. Male associations with other males and with females of differing reproductive states were examined annually and seasonally. No significant differences were found between paired and unpaired males in either spatial or temporal patterns of association with all classes of females. Lagged association analysis shows that males tend to associate with breeding females preferentially well before the breeding season starts, suggesting that they may develop affiliative relationships with females during the nonbreeding period to influence female choice later. Paired and unpaired males differed in ranging patterns as calculated by the fixed kernel method. Paired males had significantly larger overall ranging areas (95% utilization distribution (UD)) and core areas (25% UD) than unpaired males. Although these differences were significant, additional demographic analyses of lifetime probability of pair-bond formation suggest that pair bonding is the norm among adult males and that unpaired males are a transitional stage rather than an alternative strategy.

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