The origin of whales and their transition from terrestrial life to a fully aquatic existence has been studied in depth. Palaeontological, morphological and molecular studies suggest that the order Cetacea (whales, dolphins and porpoises) is more closely related to the order Artiodactyla (even-toed ungulates, including cows, camels and pigs) than to other ungulate orders. The traditional view that the order Artiodactyla is monophyletic has been challenged by molecular analyses of variations in mitochondrial and nuclear DNA. We have characterized two families of short interspersed elements (SINEs) that were present exclusively in the genomes of whales, ruminants and hippopotamuses, but not in those of camels and pigs. We made an extensive survey of retropositional events that might have occurred during the divergence of whales and even-toed ungulates. We have characterized nine retropositional events of a SINE unit, each of which provides phylogenetic resolution of the relationships among whales, ruminants, hippopotamuses and pigs. Our data provide evidence that whales, ruminants and hippopotamuses form a monophyletic group.

A depth and temperature data logger was deployed by air gun on an individual Baird's beaked whale (Berardius bairdii) off the Pacific coast of Japan. The retrieved data logger recorded 81 dives over approximately 29 h. The maximum recorded depth and the longest dive duration were 1777 m and 64.4 min, respectively. All dives were classified into three categories by depth: deep dives (>1000 m), intermediate dives (100-1000 m), and shallow dives (<100 m). Several intermediate dives generally followed a deep dive, and sequential shallow dives followed several intermediate dives in the record of the Baird's beaked whale.

Habitat models were developed from dedicated sighting survey data collected during summers between 1983 and 2006 in the North Pacific Ocean. Our aim was to examine the distribution pattern of the southern form of the short‐finned pilot whale (Globicephala macrorhynchus) in relation to the physical environment. We tested two different types of analytical procedures for habitat estimation: generalized linear models (GLMs) and ecological niche factor analysis (ENFA). The area under the receiver operating characteristic curve and the Boyce index suggested that GLM defined the core habitat well, whereas ENFA estimated the suitable habitat more correctly. These models indicated the core habitat within the subtropical gyre. Among the environmental variables used to construct the habitat models, the temperature at a depth of 200 m contributed most to both GLM and ENFA. This corresponds to the fact that the species mainly feeds on mesopelagic prey and that the axis of the Kuroshio Current, in the northwestern part of the subtropical gyre, is characterized by its temperature at 200 m. Habitat suitability in the coastal waters off southern Japan also correlated with the Kuroshio meander patterns. Thus, the southern form of the short‐finned pilot whale appears to be particularly well adapted to the ecosystem of the North Pacific subtropical gyre.

Line transect sampling is one of the most widely used methods for estimating the size of wild animal populations. An assumption in standard line transect sampling is that all the animals on the trackline are detected without fail. This assumption tends to be violated for marine mammals with surfacing/diving behaviors. The detection probability on the trackline is estimated using duplicate sightings from double-platform line transect methods. The double-platform methods, however, are insufficient to estimate the abundance of long-diving animals because these animals can be completely missed while the observers pass. We developed a more flexible hazard probability model that incorporates information on surfacing/diving patterns obtained from telemetry data. The model is based on a stochastic point process and is statistically tractable. A simulation study showed that the new model provides near-unbiased abundance estimates, whereas the traditional hazard rate and hazard probability models produce considerably biased estimates. As an illustration, we applied the model to data on the Baird's beaked whale (Berardius bairdii) in the western North Pacific.