A case of epimeletic behavior and associated acoustic records of Indo-Pacific humpback dolphins (Sousa chinensis)

TitleA case of epimeletic behavior and associated acoustic records of Indo-Pacific humpback dolphins (Sousa chinensis)
Publication TypeJournal Article
Year of Publication2018
AuthorsCheng, Zhaolong, Pine Matthew K., Huang Shiang-Lin, Wang Ding, Wu Haiping, and Wang Kexiong
JournalJournal of Mammalogy
Volume97
Paginationgyy095-gyy095
ISBN Number0022-2372
EndNote Rec Number12081
Keywordsage structure, cetaceans, climate change, fisheries, growth, killer whales, marine ecosystems, marine mammals, north pacific, ocean noise, pinnipeds, river dolphins, sequential megafaunal collapse, sirenians, whales
Abstract

Several cetacean species have demonstrated epimeletic behavior that relies on the tight social bonds between conspecifics. These behaviors and the corresponding vocalizations were recorded during a rare encounter with a group of Indo-Pacific humpback dolphins (Sousa chinensis) that included a presumed mother and deceased calf, in Sanniang Bay, China. The observed dolphins were divided into 2 apparent groups: 1) a central group with the presumed mother and her deceased calf, along with 1 to 6 other individuals swimming in synchrony with the presumed mother; and 2) a following group of several individuals, dispersed over varying distances from approximately 20 to > 300 m, that swam in the same direction as the central group. The mother was seen mostly supporting the calf’s body using her back, anterior to the dorsal fin and posterior to the melon, while the other members of the central group exhibited standing-by behaviors (i.e., remaining close to the deceased calf but not providing aid). Whistles in this context were of a longer duration and a higher complexity in the frequency modulation compared to social contexts. Several whistle types were also repeated frequently. This paper provides a detailed description of epimeletic behavior and the whistles possibly associated with that behavior in an endangered population of Indo-Pacific humpback dolphins.