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Keywords:

  • social network;
  • social structure;
  • community structure;
  • association patterns;
  • bottlenose dolphin;
  • Tursiops truncatus

Abstract

Network analysis has recently been used to delve into the dynamics of cetacean sociality. Few studies, however, have addressed how habitat shape influences sociality, specifically how linear water bodies constrain the space where individuals might interact. We utilized network and spatiotemporal analyses to investigate association patterns and community structure in a bottlenose dolphin population in a linear estuarine system, the Indian River Lagoon (IRL), Florida. Using sighting histories from a multiyear photo-identification study we examined association patterns for 185 individuals collected over a 6.5 yr period (2002–2008). The population was highly differentiated (= 0.723) and organized into six distinct social communities (= 0.544), spread in an overlapping pattern along the linear system. Social organization differed between communities, with some displaying highly interconnected networks and others comprising loosely affiliated individuals with more ephemeral associations. Temporal patterns indicated short-term associations were a significant feature of the fission-fusion dynamics of this population. Spatial analyses revealed that social structure was shaped by an individual's ranging patterns and by social processes including preference and avoidance behavior. Finally, we found that habitat “narrowness” may be a major driving force behind the sociality observed.