Strandings of Longman’s Beaked Whale (Indopacetus pacificus) in the Philippines

Abstract

Longman’s beaked whale, Indopacetus pacificus, is one of the least known of all cetacean species, with just six specimens recorded prior to 2004. Although at least twenty more specimens have been recovered from strandings since then, knowledge on the species is still very limited. In the Philippines, a stranding in Davao in 2004 was considered the first confirmed sighting of the species in the country until 2021, when a photograph of a stranded animal in Calauag, Quezon from 1965 was found in an archive and confirmed to be of I. pacificus. Sightings of Indopacetus pacificus alive at sea from the early 1990s to 2000s in the Philippines were previously unconfirmed. Subsequent review of photographs from past surveys and at‐sea sightings revealed live sightings in the eastern Sulu Sea near Negros in 1994, off the Maconacon coast in northern Sierra Madre in 2004, and near Arena Island in the Sulu Sea in 2006. Herein this study accounts for all the known strandings of the species in the Philippines and describe the specimens collected, the status of specimens to‐date based on examined stranding reports, and examination of the specimens conducted by one or more authors. To date, there are five confirmed strandings of the species, which occurred at five different sites: (1) Calauag, Quezon in 1965 (unverified length and unknown sex); (2) 5.73m male at Matina-Aplaya, Davao in 2004; (3) 5.02m male at General Nakar, Quezon in 2016; (4) 5.4m male at Gonzaga; and (5) 5.6m male at Santa Ana, both in Cagayan Province in 2018. Two individuals stranded alive but died shortly after. From three of these, the stomach contents and tissue samples were examined and collected, while the skeletons of two specimens were collected and examined. Squid beaks of Taonius sp. and Histioteuthis sp. and unidentified fish eye lenses were found in the stomach. DNA analysis using mitochondrial CytB and COI sequences showed that the specimens were indeed I. pacificus. The skeleton collected from Santa Ana, Cagayan is by far the most complete in the country. For a cetacean species that is poorly known, examination of stranded specimens offers a rare opportunity to collect information. Hence, the importance of standardising necropsy and stranding data collection protocols, training stranding first‐responders and establishing a database are emphasised.