Behaviour of Short-finned Pilot Whales Globicephala macrorhynchus (Gray, 1846) (Mammalia: Cetartiodactyla: Delphinidae) in the southeastern Arabian Sea

Abstract

The Short-finned Pilot Whale Globicephala macrorhynchus (Gray, 1846) are found in Indian waters including Lakshadweep and Andaman Islands (Vivekanandan & Jeyabaskaran 2012). They are large dolphins, and one of the largest members of the family Delphinidae. These dolphins were named "pilot whales" because it was believed that pods were "piloted" by a leader (Olson & Reilly 2009). They are tipically found in deep water on the continental shelf and shelf break. Pilot whales are nomadic and their seasonal inshore/offshore movements are related to the distribution of squid, their favorite prey (Olson & Reilly 2009). Pilot whale stomachs contain mainly oceanic squid and small fish (Mintzer et al. 2008). Distribution and movements of Short-finned Pilot Whales are regulated by prey availability (Boris 2003). In 1982-83, a strong El Niño event off the coast of southern California resulted in pilot whales avoiding the area presumably due to the absence of squid spawning (Jefferson et al. 2008). They are highly social and usually found in pods of average 20-90 individuals (Olson & Reilly 2009). Short-finned Pilot Whales, among cetaceans, are species that most frequently mass-strand possibly due to their strong social bonds (Hohn et al. 2006). The IUCN lists this species as Data Deficient in the Red List of Threatened Species (Taylor et al. 2011). In India, most cetaceans are listed under Schedule 2 Part 2 of Wild Life (Protection) Act, 1972. Kumaran (2002, 2012) has reviewed the status of cetaceans and cetacean research in India. Mass strandings of SHort-finned Pilot Whales have been reported along the southeastern coast of India (Alagarswami et al. 1973; Reghunathan et al. 2013) and sightings have been reported by Leatherwood & Donovan (1991) and Afsal et al. (2008). The behaviour of G. macrorhynchus has not been reported earlier from the Arabian Sea, and therefore, when an opportunistic sighting was made we recorded the behaviour of the pod.