Marine Biology

, 156:179

Ranging patterns of bottlenose dolphins living in oceanic waters: implications for population structure

  • Mónica A. Silva
  • Rui Prieto
  • Sara Magalhães
  • Maria I. Seabra
  • Ricardo S. Santos
  • Philip S. Hammond
Original Paper

DOI: 10.1007/s00227-008-1075-z

Cite this article as:
Silva, M.A., Prieto, R., Magalhães, S. et al. Mar Biol (2008) 156: 179. doi:10.1007/s00227-008-1075-z

Abstract

Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based surveys conducted over a 6-year period in an area of approximately 5,400 km2 (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation within the population of the Azores.

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Mónica A. Silva
    • 1
    • 2
    • 3
  • Rui Prieto
    • 2
  • Sara Magalhães
    • 2
  • Maria I. Seabra
    • 2
  • Ricardo S. Santos
    • 2
  • Philip S. Hammond
    • 1
  1. 1.Sea Mammal Research Unit, Gatty Marine LaboratoryUniversity of St AndrewsSt AndrewsScotland, UK
  2. 2.Departamento de Oceanografia e PescasCentro do Instituto do Mar (IMAR) da Universidade dos AçoresHortaPortugal
  3. 3.Biology Department, MS#33Woods Hole Oceanographic InstitutionWoods HoleUSA