Can environmental heterogeneity explain individual foraging variation in wild bottlenose dolphins (Tursiops sp.)?
Because behavioral variation within and among populations may result from ecological, social, genetic and phenotypic differences, identifying the mechanism(s) responsible is challenging. Observational studies typically examine social learning by excluding ecological and genetic factors, but this approach is insufficient for many complex behaviors associated with substantial environmental variation. Indian Ocean bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia show individual differences in foraging tactics, including possible tool use with marine sponges and social learning may be responsible for this diversity. However, the contributions of ecological factors to the development of these foraging tactics were not previously investigated. Here, we determined the relationship between ecological variables and foraging tactics and assessed whether differences in habitat use could explain individual differences in foraging tactics. We monitored 14 survey zones to identify how foraging tactics were spatially distributed and matched behavioral data to the ecological variables within each zone. Three of four foraging tactics were significantly correlated with ecological characteristics such as seagrass biomass, water depth, presence of marine sponges and season. Further, individual differences in habitat use were associated with some tactics. However, several tactics overlapped spatially and previous findings suggest demographic and social factors also contribute to the individual variation in this population. This study illustrates the importance of environmental heterogeneity in shaping foraging diversity and shows that investigating social learning by ruling out alternative mechanisms may often be too simplistic, highlighting the need for methods incorporating the relative contributions of multiple factors.
KeywordsForaging Bottlenose dolphins Ecological variation Social learning
We thank our colleagues from the Shark Bay Dolphin Research Project for their contributions to the long-term database, the Western Australia Department of Conservation and Land Management for providing logistical support and the Western Australia Department for Planning and Infrastructure for providing tidal data. The Monkey Mia Dolphin Resort and Magellan also contributed generous support during data collection. We thank L. Douglass for valuable statistical advice and R. Barr, L. Dill and anonymous reviewers for helpful suggestions. Special thanks to A. Hough, R. Lam, R. Abernethy, V. Alla, L. Barre, F. Bretos, S. Buchannan, J. Burghardt, M. Davis, H. Finn, C. Genrich, P. Greene, K. Harper, J. Laski, K. Martin, J. McLash, R. McPhie, B. Stalvie, and K. Wirsing for assistance with data collection and to J. Watson-Capps for providing the bathymetry map for the study area. Funding was provided by the Dolphins of Monkey Mia Research Foundation, the Eppley Foundation for Research (JM), Florida International University (MRH), Georgetown University (BLS, JM), the Helen V. Brach Foundation (JM), Honda Motors (BLS, JM), the Lerner-Gray Award (American Museum of Natural History) (MRH), Magellan (BLS, JM), Mercury Marine (AJW, MRH), Monkey Mia Wildsights (AJW), the National Geographic Society Expeditions Council grants (EC0151-03, EC26-98) (AJW, MRH), the National Science Foundation Graduate Research Fellowship (BLS, MRH), the National Science Foundation grant 9753044 (JM), NSERC Canada grant A6869 (L.M. Dill, AJW, MRH), the PADI Foundation (AJW, MRH) and the Shane Award (Society for Marine Mammalogy) (MRH). This research was conducted under permits from the Western Australia Department of Conservation and Land Management and the Georgetown University Animal Care and Use Committee.
- Baird RW (2000) The killer whale: foraging specializations and group hunting. In: Mann J, Connor RC, Tyack PL, Whitehead H (eds) Cetacean societies: field studies of dolphins and whales. University of Chicago Press, Chicago, IL, pp 127–153Google Scholar
- Beck BB (1980) Animal tool behavior: use and manufacture of tools by animals. Garland STPM Press, New York, p 307Google Scholar
- Bel’kovich VM (1991) Herd structure, hunting, and play: bottlenose dolphins in the Black Sea. In: Pryor K, Norris KS (eds) Dolphin societies: discoveries and puzzles. University of California Press, Berkeley, CA, pp 17–77Google Scholar
- Fragaszy DM, Perry S (eds) (2003a) The biology of traditions: models and evidence. Cambridge University Press, Cambridge, UK, p 456Google Scholar
- Fragaszy DM, Perry S (2003b) Towards a biology of traditions. In: Fragaszy DM, Perry S (eds) The biology of traditions: models and evidence. Cambridge University Press, Cambridge, UK, pp 1–32Google Scholar
- Galef BG Jr (2003) “Traditional” foraging behaviors of brown and black rats (Rattus norvegicus and Rattus rattus). In: Fragaszy DM, Perry S (eds) The biology of traditions: models and evidence. Cambridge University Press, Cambridge, UK, pp 159–186Google Scholar
- Guinet C (1991) Intentional stranding apprenticeship and social play in killer whales (Orcinus orca). Can J Zool 69:2712–2716Google Scholar
- Heithaus MR (2004) Fish communities of subtropical seagrass meadows and associated habitats in Shark Bay, Western Australia. Bull Mar Sci 75:79–99Google Scholar
- Heyes CM, Galef BG Jr (eds) (1996) Social learning in animals: the roots of culture. Academic, San Diego, CA, p 411Google Scholar
- Hunt GR, Gray RD (2003) Diversification and cumulative evolution in New Caledonian crow tool manufacture. Proc R Soc Lond B Biol Sci 270:867–874Google Scholar
- Leatherwood S (1975) Some observations of feeding behavior of bottle-nosed dolphins (Tursiops truncatus) in the Northern Gulf of Mexico and (Tursiops cf T. gilli) off Southern California, Baja California, and Nayarit, Mexico. Mar Fish Rev 37:10–16Google Scholar
- Mann J, Sargeant B (2003) Like mother, like calf: the ontogeny of foraging traditions in wild Indian Ocean bottlenose dolphins (Tursiops sp.). In: Fragaszy DM, Perry S (eds) The biology of traditions: models and evidence. Cambridge University Press, Cambridge, UK, pp 236–266Google Scholar
- Meyers LS, Gamst G, Guarino AJ (2006) Applied multivariate research: design and interpretation. Sage, Thousand Oaks, CA, USAGoogle Scholar
- Partridge L, Green P (1985) Intraspecific feeding specializations and population dynamics. In: Sibly RM, Smith RH (eds) Behavioural ecology: ecological consequences of adaptive behaviour. Blackwell Scientific, Oxford, pp 207–226Google Scholar
- Smolker RA, Richards AF, Connor RC, Pepper JW (1992) Sex differences in patterns of association among Indian Ocean bottlenose dolphins. Behaviour 123:38–69Google Scholar
- Watson-Capps JJ (2005) Female mating behavior in the context of sexual coercion and female ranging behavior of bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia. Ph.D. Dissertation, Department of Biology, Georgetown University, Washington, DC, USAGoogle Scholar