| Popis: |
Sperm whales are social cetaceans that live in matrilineal family units, and inhabit all major ocean basins from the tropics to polar regions. They produce stereotyped patterns of 3 to 40 broadband clicks, termed “codas,” that typically occur within a period of less than 3 s. Coda repertoires can be assigned to a “vocal clan,” a type of social group used to define sperm whale population structure. Extensive studies of vocal clans have been conducted in the eastern tropical Pacific (ETP); however, little is known about sperm whale coda repertoires in the western Pacific. We reviewed codas recorded from independent sperm whale groups that were acoustically and visually encountered during two marine mammal surveys conducted in the Northern Mariana Islands (10 groups) and Palau region (3 groups), in 2007 and 2012, respectively. Three bioacousticians qualitatively classified codas to type, which indicated the presence of the “+1” and “regular” vocal clan. These data are now being analyzed using multivariate methods described by Rendell and Whitehead (2003) to quantitatively classify codas from each group. The identification of vocal clans within this region has implications for understanding the culturally linked stock distribution of sperm whales across the Pacific Ocean. |
