Indian Journal of Geo Marine Sciences Vol. 47 (10), October 2018, pp. 2077-2086 Biosonar dysfunction and mass stranding of short-finned pilot whale Globicephala macrorhyncus at Manapad, southeast coast of India- An emphatic key in demystifying the enigma? R. Jeyabaskaran1,*, M. Sakthivel2, P. Rameshkumar2, J. Jayasankar1, P. Vysakhan1&V. Kripa1 1ICAR-Central Marine Fisheries Research Institute (CMFRI), Kochi - 682018, India 2ICAR-Mandapam Regional Centre of CMFRI, Mandapam Camp - 623520, India *[E-mail:
[email protected]] Received 29 December 2016; revised 27 Fabruary 2017 A mass stranding of 81 short-finned pilot whale (SFPW) Globicephala macrorhynchus along Manapad coast from 11th to 15th January, 2016 was reported. Along the same coast, 147 SFPW were reported to have stranded in the same month, 43 years ago. Morphometric measurements of stranded specimens were taken. Based on the necropsy and subsequent findings, the animals showed no obvious signs of health problems. The single most predominant cause to have triggered the recent mass stranding could be possibly biosonar dysfunction. [Keywords: Gulf of Mannar, stranding event, morphometry, kinship behaviour, necropsy] Introduction Usually, the SFPW spend most of their time at surface The short-finned pilot whales (SFPW) ((mean=76.3%, SD=18.6) during day time hours8. Globicephala macrorhynchus are one of the large Cetacean vision is very limited in underwater gregarious dolphins found in tropical and temperate and odontocetes (toothed whales) such as SFPW seas of the world. Their average group size is around produce sounds to enable them to use active 20 whales and often the pod size is up to several echolocation or biosonar10 for navigation, hundred.