Larry Hansen, a fisheries biologist with NMFS, began photoidentification
work in San Diego with Pacific coast bottlenose dolphins in September 1981 and carried out
22 boat-based surveys over the next 17 months. Defran and the CBL assumed responsibility
for the project in January 1984 and carried out 145 boat-based photoidentification surveys
in the San Diego study area over the next six years. Photoidentification research in the
Cetacean Behavior Laboratory soon discovered that Pacific coast bottlenose dolphins were
not as residential nor was their social ecology as structured as in other coastal study
locations (Weller 1991). Beginning
in 1985 the lab expanded the scope of its work to include study areas along the Baja
Mexico Peninsula 161-km south of San Diego in Ensenada (with Miriam Espinoza) and 378-km
south of San Diego in San Quintin. The CBL has also carried out photoidentification
surveys north of San Diego in Santa Barbara (319-km from SD), as well as in Orange County
(95-km from SD) with Dennis Kelly at Orange Coast College and has affiliated with Daniela
Feinholz (Pacific Cetacean Group), who has been
studying bottlenose dolphins in Monterey Bay since 1991. CBL photo identification research
in the eight years between 1984 and 1991 has been summarized in a number of manuscripts
which provide an account of the occurrence and movement patterns of bottlenose dolphins
along the California and Baja coastlines (Defran and Weller 1999, Defran et al. 1999, Caldwell et al. in prep., Hansen and Defran 1990, Defran et al. 1990, Wells et al. 1990).
In 1984 the CBL lab began behavioral work on Pacific coast bottlenose
dolphins by constructing a descriptive and illustrated ethogram (Weaver 1987). Next, the
CBL began carrying out land-based behavior observations (Hanson and Defran 1993, Simonaitis
1990) which are possible because these bottlenose dolphins live so close to the shoreline.
The focus of the lab's behavioral work has been to document the impact of a wide range of
temporal and ecological variables on dolphin behavior states such as travel, feed and
social. In this context the CBL has examined the impact of variables such as time of day,
tidal state, substrate type, ocean and kelp condition, wave height, water depth, and
season on diurnal behavior, nocturnal behavior (Day and Defran 1995), behavior state
duration (Tepper and Defran 1995),
foraging strategies, and the sequential relatedness of behavior states (Barre and Defran 1995). By the end of
August 1995 the CBL had accumulated four years of land-based and one year of boat-based
behavioral observations using a focal-group sampling protocol. Currently, the CBL is
carrying out a theodolite-based analysis of bottlenose dolphin foraging strategies in the
San Diego study area (Ward 1998).
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| Eric Howarth prepares to deploy a sonobuoy from the Barbara Joy |
|---|
The Cetacean Behavior Laboratory began conducting acoustical studies on bottlenose
dolphins in 1995 with the work of Greg Campbell who recorded
dolphin vocalizations in Belize and then later in the San Diego study area. The goal of
this and related work has been to examine possible population-specific differences in the
bottlenose dolphin's whistle emissions. Since 1997, another CBL graduate student, Eric Howarth, our self-described webslave/master, began a series
of innovative pilot studies designed to convert U.S. Navy Sonobuoys into floating and
transmitting listening devices suitable for detecting and recording bottlenose dolphin
sounds. A floating array of these sonobuoys, properly placed in the study area, allows us
to record dolphin vocalizations as well as determining the location of the vocalizing
dolphins. Most recently, Julie Oswald, another CBL graduate
student, has begun analyzing whistles from cetacean species recorded during NMFS sponsored
research cruises in the eastern tropical Pacific.
Between March of 1992 and March 1996 the CBL formed a research partnership with Oceanic Society Expeditions in San Francisco to study the population dynamics and behavioral ecology of bottlenose dolphins in the Carribean waters surrounding Turneffe Atoll, a coral reef/mangrove archepelego located 35 miles offshore from Belize in Central America. The focus of this continuing research was on the home range, abundance, distribution, social ecology and acoustic characteristics of this population of bottlenose dolphins (Bilgre et al. 1995, Campbel1 1995).
Belize, formerly British Honduras, is a small nation in Central America, located on the Caribbean Sea south of Mexico’s Yucatan Peninsula. Belize boasts the second largest barrier reef in the world and three of the Western Hemisphere’s four coral reef atolls. In 1992 Oceanic Society Expeditions, a non-profit organization committed to conservation, began a research project studying bottlenose dolphins at Turneffe Atoll. Turneffe Atoll, located 32 km off the mainland of Belize, is the largest of the three Belizean Atolls and is a coral reef/mangrove archipelago. Between March 1992 and March 1996 researchers for the Belize Bottlenose Dolphin Research Project conducted boat based photographic surveys intended to photographically identify bottlenose dolphins encountered in the study area. The partnership between Oceanic Society and the Cetacean Behavior Laboratory began in March 1993 when Barbara Bilgre of CBL began research in Belize. Barbara’s work, which was conducted between March 1993 and December 1994, examined the abundance, distribution and social ecology of bottlenose dolphins in Turneffe Atoll. In March 1995, Greg Campbell began collecting photographic and acoustic data in Turneffe for his Master’s thesis. The data Greg collected is being used to determine population parameters, social ecology and whistle repertoire of dolphins in the atoll. A summary of the findings of the four year photographic study will be submitted for journal publication in fall 1998.
In an attempt to gain information on the bottlenose dolphins in other areas of Belize, the Belize Bottlenose Dolphin Project moved from Turneffe Atoll to Spanish Bay Resort in the Drowned Cayes region in February 1997. The Drowned Cayes are several mangrove islands located approximately 8 km offshore from Belize City and a few kilometers west of the Belize Barrier Reef. Greg continued photographic and acoustic data collection in this new study area between February 1997 and April 1997. The data collected during this research has offered us the opportunity to learn more about the population parameters and social ecology of bottlenose dolphins inhabiting the coral reef/mangrove/seagrass habitat characteristic the Belizean region (Campbell 1998). The photographic results of this study are summarized in Campbell 1998. We are currently carrying out comparisons between Drowned Cayes sightings the 81 individuals photographically identified in the Turneffe Atoll study area, 16 km to the east. These comparisons should allow us to gain further insight into the range and residence patterns of the Turneffe dolphins. Presently, Kecia Kerr, is conducting research in the Drowned Cayes area designed to yield a size estimate for this population of bottlenose dolphins, as well as a better understanding of their home range, site fidelity, habitat usage and social ecology. Kecia began data collection in July 1998 and plans to continue field work until December 1999.
Other research links can be found at CBL
Links.