Replacement dolphins? Social restructuring of a resident pod of Atlantic bottlenose dolphins, Tursiops truncatus, after two major hurricanes

Abstract

Environmental variations can influence the structure of ecological communities that in turn alter the grouping and association patterns of social communities. This study compares the social structure of bottlenose dolphins in the Bahamas before and after two major hurricanes. Approximately 30% of regularly seen individuals disappeared after the hurricanes, with an equal number of immigrants arriving afterwards. The primary goal of this study was to quantitatively describe social structure changes occurring after this large-scale emigration (or death) and subsequent immigration of individuals using the social analysis program, SOCPROG 2.3. The pre-hurricane results revealed one community with association patterns that were consistent with previous work on this population as well as other welldocumented populations. Post-hurricane associations revealed that the community split into two distinct units, whose members associated highly within, but rarely between units. Association patterns varied between units. Immigrants assimilated well into the population, especially males. Over half of the post-hurricane associations involved immigrants, the majority between residents and immigrants, and primarily involving immigrant males. The costs/benefits of choosing to associate with an immigrant individual differ between males and females and may have been the driving force for the changes in social structure that occurred.

Disentangling social networks from spatiotemporal dynamics: the temporal structure of a dolphin society

“…Such a nested ranging behaviour among Guiana dolphins from different modules suggests that space use patterns are not enough to explain the modular topology observed in this study. However, nonsocial factors can still be influencing this dolphin social network (see Whitehead 1999;Parsons et al 2009;Elliser & Herzing 2011). We showed that the population dynamics has split this society into temporal modules.…”

“…Lehmann & Boesch 2004), which may define distinct social units (e.g. Elliser & Herzing 2011). The Guiana dolphin population underwent a marked population turnover, with a change in the population composition from the beginning to the end of the study.…”

Severe Karenia brevis red tides influence juvenile bottlenose dolphin (Tursiops truncatus) behavior in Sarasota Bay, Florida

“…Studies typically either examine the effects of anthropogenic disturbance from boats and tourism ( e.g., Nowacek et al 2001; Constantine et al 2004; Bejder et al 2006 a , b ; Dans et al 2008; Stockin et al 2008) or human‐generated noise in the marine environment ( e.g., Nowacek et al 2007, Weilgart 2007, Tyack 2008). However, a growing body of research is focusing on the effects of natural disturbance regimes such as HABs (Fire et al 2008 b , Goldstein et al 2008, Fire et al 2009, Torres de la Riva et al 2009), periodic environmental oscillations including El Niño (Wells et al 1990, Benson et al 2002, Lusseau et al 2004, Whitehead and Rendell 2004, Keiper et al 2005, Ballance et al 2006, Leaper et al 2006, Trathan et al 2007), and catastrophic events such as hurricanes (Miller et al 2010; Elliser and Herzing 2010) on marine mammal populations.…”

Social structure of the declining resident community of common bottlenose dolphins in the Sado Estuary, Portugal

“…In Little Bahama Bank, two hurricanes caused the loss of 30% of a population that comprised only one community (Elliser & Herzing, 2010). The remaining individuals formed two separate communities, each integrating immigrants.…”