 |
|
Since 1985 the Cetacean Behavior Laboratory has been conducting land-based behavioral studies within the San Diego area. Projects have included an illustrated ethogram (Weaver 1987), analyses of feeding ecology (Hanson and Defran 1993) and duration (Tepper 1996), sequential relationships between behavior states (Barre 1994), nocturnal behavior (Day 1998) and theodolite studies of the relationship between behavior state, swim speed and distance from shore (Ward 1998). Karen Johnson and Martisha Liefer have recently begun behavior studies which build on this research base and seek to refine our understanding of free-ranging bottlenose dolphin behavior. Their work involves recording detailed concurrent information about behavioral events and the temporal and geometric features of behavior states. In this research Karen and Martisha are working in collaboration with Ann Weaver, a former CBL graduate student who has recently proposed an innovative methodological approach for studying cetacean behavior (Weaver et al. 1998). Their long-term goal is to improve the measurement of free-ranging dolphin behavior by providing a clearer links for associating specific surface patterns with specific dolphin behavior states.
Martisha’s efforts are concentrated on recording behavioral events which are considered "instantaneous" in that they are short in duration and are counted rather than timed. Behaviors such as leaps and tail slaps are examples of instantaneous events. During land-based field work Martisha records all-occurrence data for 30 pre-determined behavior events in a continuous succession of two-minute time intervals. At the end of a two-minute interval she also records group size and behavior state. After data collection she plans to derive rate of occurrence for each behavioral event in each state. Along with determining which events occur in which states and at what rate, she would like to compare these rates over a range of temporal (e.g., time of day, season) and environmental (e.g., substrate type, distance from shore) variables.
Karen utilizes instantaneous-scan sampling to record data on several behavioral dimensions (i.e., dispersion: spacing between individual dolphins with respect to one another in terms of dolphin body lengths). Each dimension has been scaled along biologically meaningful qualitative and quantifiable levels. For example, the tempo of behavior is judged to be slow, medium, or fast. At the time of this summary (Sept 1998) Karen and Martisha are conducting inter-observer reliability assessments of the events and dimensions judged in the field. Upon completion of data collection and analysis, they hope to show that there are specific events and levels of each dimension that can be identified for specific dolphin behavior states. The end goal is to provide a reliable observational method for dolphin behavioral research.
References
Barre, L. M. 1994. Behavioral sequence analysis of bottlenose dolphins (Tursiops truncatus). Master's thesis, San Diego State University, California.
Day, J. 1998. Nocturnal movements and behavior patterns of Pacific coast bottlenose dolphins, (Tursiops truncatus). Master's thesis, San Diego State University, California.
Hanson, M. T. and R. H. Defran. 1993. The behavior and feeding ecology of the Pacific coast bottlenose dolphin, (Tursiops truncatus). Aquatic Mammals 19:127-142.
Tepper, E. 1996. Feeding duration in the Pacific Coast bottlenose dolphin (Tursiops truncatus). Master's thesis, San Diego State University, California.
Ward, B. 1998. Movement patterns and feeding ecology of the Pacific Coast bottlenose dolphin (Tursiops truncatus). Master's thesis, San Diego State University, California.
Weaver, A. C. 1987. An ethogram of naturally occurring behavior of bottlenose dolphins, Tursiops truncatus, in southern California waters. Master's thesis, San Diego State University, California.
Weaver, A. Ch. F., M. Liefer, K. Johnson, and R. H. Defran. 1998. Method for identifying behavior states among free-ranging bottlenose dolphins, Tursiops truncatus. Measuring Behavior ’98 Conference, August 18-21, Groningen, The Netherlands.
Last updated 11/14/99