We present an observational method for identifying behavior states exhibited by free-ranging bottlenose dolphins. First is a description of the method, which is based on interpreting surface-visible dolphin behavior on eleven criteria: formation, dispersion, orientation, predictability of next surface location, tempo, synchrony, surface: submergence ratio, cohesion, group movement, homogeneity and behavioral events. We describe each criterion and explain how it can be applied in the field.

Second is a qualitative description of 18 dolphin behavior states that were identified using the criteria. These data were collected during 114 h of direct observation of bottlenose dolphins on 80 boat surveys of two sites, Cape Lookout, North Carolina, USA and Bahia de la Paz, Baja California Sur, Mexico, June 1992-August 1993. We present these data in tabled form to illustrate how individual dolphin behavior states are characterized by unique combinations of the criteria listed above.

Third is quantitative support for the unique combinations of criteria that characterize individual dolphin behavior states. These data are drawn from 86 hours of direct observation of bottlenose dolphins during 52 land-based surveys of the San Diego County study area between May-Dec 1997. Each criterion, except behavior events, was partitioned into biologically meaningful, qualitative categories, e.g., the criterion dispersion was partitioned into three qualitative categories to quantify inter-animal distances (2, 2-5, and 5 dolphin body-lengths). Instantaneous scan samples of qualitative categories were collected on group behavior at 2-minute intervals. All-occurrence data on 29 predetermined behavior events were collected during two-minute intervals. We present quantitative support for detailed qualitative descriptions of three dolphin behavior states on six criteria. An example of a detailed qualitative description is the following for Indeterminate Travel. Characteristic criteria include behavior events producing rhythmic forward progress at a slow to moderate tempo in the same headfirst orientation in a general direction with occasional meandering. Dolphins tend to remain close to the surface in a moderate to high surface: submergence ratio. Cohesion is moderate due to a tendency for some group members to incorporate other activities while or instead of traveling. The criteria formation, dispersion, synchrony, as well as other activities, tended to be more variable. Formation tends toward staggered ranks; in larger groups, several subgroups travel in ranks aligned in long formation with respect to one another. Ranks in long formations can become independent ranks. Changes in formation affect dispersion; dolphins stay in the proximity of one another. Synchrony is partial, exhibited primarily among members of the same subgroups and rarely between subgroups. "Other activities" include intermittent episodes of affiliative socializing or incipient sexual exchange, indicated by leaps, double bows, a series of low intensity breaches, skims, brief exposure of various body parts at the surface or slow-paced rafting; one or more dolphins may surf.

The systematic evaluation of criteria typical of all dolphin states improves the measurement of free-ranging dolphin behavior by providing a clear rationale for associating specific surface patterns with specific dolphin behavior states.