We examined the habitat use of the Indo-Pacific bottlenose dolphin Tursiops aduncus around Amakusa-Shimoshima Island, Japan. Of the approximately 200 individuals that resided in the waters north of this island, about 30 individuals moved to the south around Nagashima Strait, with different environments, and then disappeared. The habitat use of these dolphins in the south was examined using land- and boat-based surveys and compared with that in the north. The ferry crew sightings were also analyzed. Intensively used areas, which were estimated using a first-passage time analysis, were shallow waters close to the shore, located around small islands or in coastal areas facing the strait. Resting behavior, characterized by low apparent moving speed and synchronous dives, was observed in the intensively used areas. The dolphins tended to be on the south side of the strait in daytime hours, and the similar trend was observed at low and ebb tides. The habitat use, such as having certain resting places, possible habitat areas at night, and tidal-affected distribution was similar to that in the north. Resting places were scattered and not stable throughout the study period. The disappearance of dolphins may be due to drop in suitability of resting places.

Captive condition sometimes evokes behaviors that are not observed in animals in the wild. A confirmation of the behaviors in the wild is needed to exclude the possibility of captivity-specific behaviors. Narrow-ridged finless porpoises are reported to produce two sound types for communication: “packet sound”, which is a series of pulses with repeated pulse packets (a sound series consisting of a few pulses with irregular, short inter-pulse intervals), and “burst pulses”, which are a pulse train with significantly shorter inter-pulse intervals compared to packet sound. Burst pulses were reported from wild narrow-ridged finless porpoises of Seto Inland Sea–Hibiki Nada population in Japan, while the packet sound was only recorded in captive conditions. Here, we report the packet sound as well as burst pulses from wild narrow-ridged finless porpoises of Ise–Mikawa Bays population in Japan. We found six packet sounds and six burst pulses out of 5 h recording of a self-contained underwater sound recorder, at a frequency of 0.020 times/min for each sound type. It is suggested that packet sound is produced by not only captive but wild narrow-ridged finless porpoises. Future studies should focus on the behavioral state when producing communication sounds.

Assamese macaques (Macaca assamensis) and rhesus macaques (M. mulatta) are sympatrically distributed in Nepal but differ in many traits. Data on 11 groups of Assamese macaques and 13 groups of rhesus macaques in northwestern Kathmandu show that Assamese macaques inhabited only protected forests in Shivapuri Nagarjun National Park, whereas rhesus macaques inhabited even small forests disturbed by people in temples close to cultivated and urban areas, frequently raided crops, and were provisioned. Assamese macaques inhabited higher altitude and formed smaller groups with more adult males and fewer immatures than rhesus macaques. Rhesus macaques' proclivity to be provisioned supported their large groups. However, their strict dominance hierarchy might make low-ranking males solitary, whereas many males of Assamese macaques might be able to stay together because of their affiliative relationship with other males. In Nepal, Assamese macaques might adopt more K-reproductive strategies with a larger body, fewer offspring, and lower twin frequency in stable circumstances, compared to rhesus macaques. Competition for resources promotes niche separation in food choice and habitat use, which might strengthen the inter-species difference and make their coexistence possible. We recommend careful maintenance of forests to protect Assamese macaques, and effective managements of provisioned and crop-raiding rhesus macaques.

Received 19 September 2023. Accepted 25 December 2023.