Abstract: Spinner dolphins (Stenella longirostris) use Maku’a Beach, a small bight along the Wa’i’ana’e coast of O’ahu, as a rest site. Behavior and use patterns of Maku’a Beach by spinner dolphins and swimmers were studied in July and August of 1995 to provide baseline data on the dolphin population and to assess potential impacts of swimmers on the dolphins’ resting behavior. Dolphins were observed on 52 out of 53 days, and they entered the area between 0545 and 0845 h. Their departure time varied widely. Average school size was 67 ± 0.6 SE and decreased with time of day. The most common aerial behaviors were slaps, leaps, and spins, respectively, with a peak in aerial behavior in late afternoon associated with schools moving offshore. The number of swimmers in the study area was highest on weekend mornings (x = 12 ± 0.6 SE), with a maximum of 63 people in the water at the same time. Rest appeared delayed and compressed in this population of dolphins as compared to other studies and may be a response to the presence of swimmers in the morning. The results suggest a potential adverse impact of swimmers on the dolphins’ resting patterns, with earlier departure times and shorter periods of dive behavior indicative of rest.

Key Words: SPINNER DOLPHIN; STENELLA LONGIROSTRIS; MAKU’A BEACH; O’AHU; HAWAI’I; RESTING PATTERNS; RESTING BEHAVIOR; SWIMMERS; HUMAN IMPACT

Document Type: Research article

DOI: 10.1578/AM.31.4.2005.403

Page Numbers: 403 – 412