Definite records of Sperm Whale Physeter catodon (Linnaeus), Spinner Dolphin Stenella longirostris (Gray) and Bottlenose Dolphin Tursiops truncatus(Montagu) (Mammalia: Cetartiodactyla) in the Arabian Sea

Satish Pande 1, Niranjan Sant 2, Shivkumar Pednekar 2 & M.S. Pradhan 3

1,2ELA Foundation, C-9, Bhosale Park, Sahakarnagar-2, Pune, Maharashtra 411009, India

3 B-2, Kalpanamati Housing Society, Aundh Gaon, Pune, Maharashtra 411007, India

Email: 1 satishpande@hotmail.com, pande.satish@gmail.com

Date of publication 26 March 2009

ISSN 0974-7907 (online) | 0974-7893 (print)

Editor: Kumaran Sathasivam

Manuscript details:

Ms # o1881

Received 12 November 2007

Final received 28 August 2008

Finally accepted 12 January 2009

Citation: Pande, S., N. Sant, S. Pednekar & M.S. Pradhan(2009). Definite records of Sperm Whale Physeter catodon (Linnaeus), Spinner Dolphin Stenella longirostris(Gray) and Bottlenose Dolphin Tursiops truncatus (Montagu) in the Arabian Sea. Journal of Threatened Taxa 1(3): 180-181.

Copyright: © S. Pande, N. Sant, S. Pednekar & M.S. Pradhan 2009. Creative Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium for non-profit purposes, reproduction and distribution by providing adequate credit to the authors and the source of publication.

Acknowledgement: ELA Foundation, Ecological Society, both from Pune and Indian Coast Guard jointly conducted the pelagic bird survey. First three authors participated in the survey and the last author confirmed the identification of the cetacean species. We thank Vice Adm. M.P. Awati (Retd.) for recommending the project proposal to the competent authorities. We thank Director General Coast Guard, New Delhi and Chief of Coast Guard, Western Region and Comdt. S. Paramesh, CO CGS ANNIE BESANT and his crew for all the help. Asst. Comdt. Varun Upadhyaa first sighted the shallow water-jet blows over the sea surface and alerted us of the presence of whales. Thanks are also due to Dr. Anil Mahabal, O/c ZSI, WRS, Pune for encouragement.

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In a recent pelagic bird survey of the Arabian Sea carried out from Mangalore port to the Lakshadweep Archipelago and back (Pande et al. 2007), a watch was also kept for marine mammals. Some of the dolphin and whale species that were encountered were counted over 40 hours of daytime by keeping a watch from the deck during the entire survey period from 12 March to 16 March 2006. Observations were documented with digital photography and video recording.

A) Sperm Whale Physeter catodon(Linnaeus)

Family:Physeteridae

Species: Physeter catodon (Linnaeus) = Physeter macrocephalusLinnaeus

Large square head, small eyes, shriveled brownish body with prune-like wrinkles, triangular hump on the back, blowhole situated on the left side on the head and habit of partial breaching helped in identifying the species. The whales were seen partially breaching every few minutes for a total observed period of about ten minutes. The entire body was never seen above water surface. The approximate length of two whales could be estimated since they briefly swam parallel to our ship with head and flipper seen intermittently, enabling us to judge their entire body length, when a comparative estimate was made. The other three were some distance from us. However, it should be stated that we could have under-estimated the length.

The whales were observed blowing shallow water jets every minute or so through their left-sided dorsal blowholes that were clearly visible when the whales partially breached above the sea surface. The most significant breach was seen before the final dive. Total 5 Sperm Whales were seen. The age of whales could not be determined. Two whales closely followed the ship for about 10 minutes and the others remained about 150m away from the ship. Whales were first noticed due to the spouting of water from the blowhole. They crossed the stern side of the ship on one occasion from starboard to port side and the nearest distance to which they approached was 8 m from the ship.

The Sperm Whales were sighted at 0740hr on 16 March 2006 at 12003’39’’N & 73059’48’’E. The depth of sea at this place was 1818m, the atmospheric pressure was 1014 mb, wind velocity was 10-12 knots in northwesterly direction and ambient temperature was 340C. The nearest mainland on the west coast of India was Kottikonnu at 70 nautical miles and the closest island of Lakshadweep Archipelago was Chetlatat 77 nautical miles.

Photographs were critically examined and identification was confirmed from key features (Alfred et al. 2006). The present documentation is a definite record of the Sperm Whale in the Indian marine waters. The earlier sightings have been described in deep waters more than 200m and from east and west coasts off Gujarat, Maharashtra, Kerala, Tamil Nadu, Pondichery, Andaman and Nicobar Islands and Lakshadweep Islands. (Pillay 1926; Prater 1971; Kumaran2000; Menon 2003). Population of Sperm Whale is unknown, social unit is of 1 to 50, occurrence rare. IUCN status Vulnerable (Taylor et al. 2008); Indian Wildlife (Protection) Act, Schedule II/Part I (Alfred et al. 2006).

B) Dolphins

Family: Delphinidae

Dolphin sightings were between Mangalore and Lakshadweep archipelago. The depth of the Arabian Sea varied from 50m to 1800m and atmospheric pressure was 1014mb. The dolphins were seen at a distance of 10 nautical miles from the Mangalore coast to 15 nautical miles from the coast of several Lakshadweep Islands and also in the marine waters in between.

1. Spinner Dolphin: Stenella longirostris(Gray, 1828): The spectacular spinning leaps and acrobatics, the erect triangular conspicuous darker dorsal fin, creamy white patch on underside, distinct long and slender beak and the long flippers confirmed their identification. Schools of 8 to 15 dolphins totaling 58 were encountered during the entire survey period. All the sightings were in the early morning and in the evening. The marine dolphins kept following the ship for some time never approaching nearer than 50m on each occasion and they were not seen near the coast. Their population is unknown and they occur in warm waters of both the coasts. IUCN status Data Deficient (Hammond et al. 2008); Indian Wildlife (Protection) Act, Schedule II/Part I (Alfred et al. 2006)

2. Bottlenose Dolphin Tursiops truncatus (Montagu, 1821): The distinctly visible forehead during breaching, short beak, curved fin with backward concavity, longish flippers and behaviour of executing somersaults and dives but not leaps high above water confirmed their identification. They were seen in offshore waters. A total of 12 Bottlenose Dolphins were counted, they were in smaller congregations of 3 to 5 individuals and they briefly followed the ship but kept a distance of at least 25m from the ship. They occur in tropical waters and their population is not known (Menon 2003). IUCN status Least Concern (Hammond et al. 2008); Indian Wildlife (Protection) Act, Schedule II/Part I (Alfred et al. 2006)

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