In this study we (1) synthesized 65 yr of odontocete stranding data around the main Hawaiian Islands (1937Islands ( -2002; (2) analyzed stranding patterns and trends over time; and (3) compared occurrence patterns based on sightings of live animals with stranding data and evaluated the compatibility of these data sets. From 1937 to 2002, 202 odontocete strandings were recorded by the National Marine Fisheries Service, Pacific Islands Regional Office. Strandings increased through time due to increased reporting effort and occurred throughout the year. The four most common of 16 species reported were Kogia spp. (18%), spinner dolphins (Stenella longirostris) (15%), striped dolphins (Stenella coeruleoalba) (11%), and sperm whales (Physeter macrocephalus) (10%). The highest proportion of strandings was recorded on O'ahu (48%), followed by Maui/ Lāna'i (24%), Kaua'i (12%), Hawai'i (11%), and Moloka'i (5%). Comparison with four previously published live animal survey studies suggests that stranding records are a good indicator of species composition and yield reasonable data on the frequency of occurrence of species in the region they cover.

Between 2007 and 2009, we witnessed three aggressive interactions between harbor porpoises and bottlenose dolphins in Monterey Bay, California. This is the first time such aggression has been documented in the Pacific, and the first time a harbor porpoise was collected immediately after witnessing its death, inflicted by bottlenose dolphins. Of the bottlenose dolphins present, 92% were males either confirmed (61%) or putative (31%). Since 2005, 44 harbor porpoise deaths inflicted by bottlenose dolphins were documented in California. Aberrant behavior was rejected as a cause of aggression, based on widespread documentation of similar behaviors in other populations of free-ranging bottlenose dolphins. The evidence for interspecies territoriality as a form of competition for prey was weak: there is little dietary overlap and there are differences in bottlenose dolphin and harbor porpoise distribution patterns in California. Object-oriented play was plausible as a form of practice to maintain intraspecific infanticidal skills or a form of play to maintain fighting skills between male associates. Contributing factors could be high-testosterone levels, as attacks occurred at the height of the breeding season, and/or a skewed operational sex ratio. Ultimately, we need more information about bottlenose dolphin social structure at the time of the aggression.

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 (xstudy area was highest on weekend mornings (study area was highest on weekend mornings (= 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.

This initial research is a component of the first comprehensive study on the occurrence, movement patterns, and behavioral ecology of bottlenose dolphins (Tursiops truncatus gilli) in the coastal waters

The behavioral and predatory patterns of Gulf of Alaska (GOA) transient killer whales (Orcinus orca) were studied between 2000 and 2005 using remote video and vessel‐based observations near the Chiswell Island Steller sea lion (Eumetopias jubatus) rookery and in the broader Kenai Fjords (KF) region of the northern GOA. GOA transient killer whales were observed on 118 d over the 6‐yr period; the median group size was two (range: 1–9). Nine predation events were observed from vessels and an additional sixteen were inferred from remote video studies; all involved Steller sea lions. Estimates from field observations suggest that fifty‐nine sea lions were consumed over the summer seasons of 2002–2005; whereas estimates based on published caloric requirements of transient killer whales would suggest a loss of 103 sea lions over the same time period. GOA transients spent a large proportion (43%) of their time resting which may be a strategy for conserving energy. Predation on sea lion pups at the Chiswell Island rookery was greatest during years when a single killer whale was foraging alone and when a 1.5‐yr‐old calf was evidently being trained to handle prey. Predation on pups was low during years when killer whales were foraging in groups and were observed and presumed to be taking mostly juvenile sea lions. Our study suggests that GOA transients are having a minor effect on the recovery of Steller sea lions in the GOA.