Grampus griseus
Scientific Name:-
Grampus griseusCommon Name:-
Risso’s / Grey Dolphin
Malayalam Name:-
Risso Dolphin
Category:-
Mammals
Status:-
Least Concern ver 3.1 in Red List Category. Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), and in Appendix II of the Convention on Migratory Species (CMS).
Indian Wildlife (Protection) Act: Schedule II
Description:-
This species has a relatively large anterior body and dorsal fin, while the posterior tapers to a relatively narrow tail. The bulbous head has a distinct vertical crease or cleft along the anterior surface of the melon. It has a tall, curved dorsal fin that tends to be more erect in males and long flippers. The flukes are broad and curved with a deep notch and the tailstock is slender. Body is dark gray with a white underside that becomes whiter with age as the heavy criss-crossed scars that cover their bodies increase. It has a white anchor-shaped patch on the ventral side.
One of the largest dolphins found in India, this species may grow up to 14.1 feet (4.3 m) in length and may weigh 300–500 kilograms. Females mature sexually at ages 8–10, and males at age 10–12. These dolphins typically travel in groups of 10–51. They feed almost exclusively on squids and they are mostly nocturnal.
Threats:-
Incidental catches in fishing gears has been reported from Kerala.
Remark:-
Risso's dolphin is named after Antoine Risso, whose description formed the basis of the first public description of the animal, by Georges Cuvier, in 1812.
Habitat:-
Risso's dolphins are pelagic, mostly occurring seaward of the continental slope. Their preferred environment is just off the continental shelf on steep banks, with water depths varying from 400–1,000 m and water temperatures 15-20°C.
Synonyms:-
Delphinus aires G. Cuvier, 1812 ; Delphinus griseus G. Cuvier, 1812; Delphinus griseus Gray, 1828; Delphinus orca Temminck & Schlegel, 1841; Delphinus risso Risso, 1826; Delphinus rissoanus Desmarest, 1822; Delphinus rissoi Gervais, 1859; Globicephalus rissii Hamilton, 1837; Gramphidelphis griseus Kellogg, 1940; Grampidelphis exilis Iredale & Troughton, 1933; Grampidelphis kuzira Iredale & Troughton, 1933; Grampus cuvieri Gray, 1846; Grampus richardsoni Gray, 1850; Grampus rissoanus Murie, 1871; Grampus sakamata Gray, 1846; Grampus sakata Tomilin, 1957; Grampus sowerbianus Fischer, 1881; Grampus stearnsii Dall, 1873; Phocaena griseus F. Cuvier, 1836; Phocaena rissonus F. Cuvier, 1836
References:-
James, P. and Mohan, R. S. (1987). The Marine Mammals of India. Marine Fisheries Information Service Technical and Extension Series 71:1-13.
Jayasankar, P. and Anoop, B. 2010. Identification of Marine Mammals of India. Narendra Publishing House, Delhi.
Jefferson, T.A., Leatherwood, S. and Webber, M.A. 1993. FAO Species identification guide. Marine Mammals of the World: UNEP / FAO, Rome, 320 pp.
Jefferson, T. A., M. A. Webber and R. L. Pitman. (2008). Marine mammals of the world. Academic Press, Amsterdam.
Kumaran, P.L. 2012. Cetaceans and cetacean research in India. J. Cetacean Res. Manage., 12(2): 159–172.
Sathasivam, K. 2004.Marine Mammals of India. University Press, Hyderabad.
Thiagarajan, R., Krishna Pillai, S., Balasubramanian, T.S. and Chellam, A. 2000. Accidental catch of three Risso’s dolphin at Beemapally, near Vizhinjam. Mar. Fish. Info. Serv., T & E Ser., 163: 10.
Vivekanandan, E. and Jeyabaskaran, R. 2012. Marine Mammal Species of India. Central Marine Fisheries Research Institute, Kochi, 228pp.
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J.K.B., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. 2012. Grampus griseus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. <www.iucnredlist.org>. Downloaded on 15 August 2013.