Social ecology of bottlenose dophins in Monterey Bay, California

Maldini, Daniela and Nilsson, Peter (2001) Social ecology of bottlenose dophins in Monterey Bay, California. In: The Society for Marine Mammalogy -14th Biennial Conference , 28 November - 3 December 2001 ,Vancouver, British Columbia, Canada, p. 1.

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Between 1990 and 1995, Pacific coastal bottlenose dolphins (Tursiops truncatus gillii) were studied using photo-identification during 228 boat-based surveys of the coastal strip (<1 km offshore) between Marina and New Brighton Beach in Monterey Bay (18 km of coastline). The study period encompassed 3 regular (1990, 1991 and 1995) and 3 El Niño years (1992, 1993, 1994). Based on dorsal fin markings, 97 unique individuals were identified. Eighteen animals (19%) showed a high level of site fidelity (defined as presence in at least 5 of the 6 years), although their overall range was larger than the study area. Thirty-eight animals (39%) were transient, leaving for periods of time, and 41 (42%) were occasional encounters. The rate of discovery indicated a pulsed recruitment of new individuals into the study area, with periods of stable school composition, especially during non-El Nino years, and periods of high school fluidity. Encounter rate was significantly higher in El Niño (81%) than non-El Niño years (61%). School size averaged 16 individuals (C.I.3, =0.05) and was significantly larger in El Niño years. Schools where calves were present were twice as large (mean=15; S.D.=8) than schools without calves (mean=8; S.D.=6). Newborns represented 12% of the sightings and were seen year round with a peak in summer and fall. Crude birth rate ranged between 0.09 and 0.17 (mean=0.13; S.D.=0.03). Five females calved in consecutive years and a resident female calved once a year for the duration of the study, possibly indicating a high rate of mortality for calves in this area. Individuals often traveled as subgroups of more consistent composition than the school itself, possibly indicating that a stronger social bond exists within these units which may function as “bands” (sensu Wells 1991) of same sex individuals traveling within a larger school of mixed composition. (ppt file of poster)

Item Type: Conference or Workshop Item
Title: Social ecology of bottlenose dophins in Monterey Bay, California
Personal Creator/Author:
Refereed: No
Page Range: p. 1
Date: 2001
Contact Email Address:
Event Title: The Society for Marine Mammalogy -14th Biennial Conference
Event Type: Conference
Event Location: Vancouver, British Columbia, Canada
Event Dates: 28 November - 3 December 2001
Subjects: Ecology
Item ID: 2670
Depositing User: Dr Daniela Maldini
Date Deposited: 26 Oct 2009 13:09
Last Modified: 09 Dec 2010 09:59
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