First record of the Spinner Dolphin Stenella longirostris longirostris (Cetacea: Delphinidae) for Kosrae, Micronesia

The Spinner Dolphin Stenella longirostris longirostris (Gray, 1828) has been reported from most of the island groups from Micronesia, except for Kosrae. On 25 June 2014 we observed a pod of about 10 dolphins at Molsron Yela, Kosrae. Our photos of the dolphins confirm their identity as S. l. longirostris, based on the extremely long and slender snout combined with the tricolored pattern of a dark gray cape, gray sides, and white belly. This provides the first documented record for Kosrae.


Introduction
Marine mammals are frequently observed in Micronesia, yet few are positively identified and even fewer are reported in the scientific literature, especially from islands seldom visited by biologists (Eldredge 1991, Wiles 2005).The Spinner Dolphin Stenella longirostris (Gray, 1828) has a pantropical distribution and is represented by 4 subspecies, of which 1 occurs in coastal southeast Asia (S. l. roseiventris), 2 occur in the tropical eastern Pacific Ocean (S. l. orientalis and S. l. centroamericana along coastal Central America), and 1 is pantropical (S. l. longirostris) (Perrin and Gilpatrick 1994, Reeves et al. 2002, Perrin et al. 2007, Perrin 2009).Its conservation status is currently regarded as 'data deficient' (Bearzi et al. 2012).In Micronesia, S. longirostris has been previously reported from most of the major island groups, including Palau, Yap, Guam, the Northern Marianas, Chuuk, Pohnpei, and the Marshall Islands (e.g.Miyazaki and Wada 1978, Gilpatrick et al. 1987, Eldredge 1991, Eldredge 2003, Stinson 1994, Trianni and Kessler 2002, Fulling et al. 2011, McNulty 2013), but not from Kosrae (Fig. 1).In this note we report the first confirmed record of S. l. longirostris for Kosrae, which is the easternmost high island in Micronesia (Fig. 2).

Methods
While residing in Kosrae from 27 August 1981 to 1 January 1982 and from 15 January to 21 May 1982, the first author (FEH) observed 61 unidentified dolphins along the coast during the months of August, September, February, and March.They occurred in pairs or small pods.A pod of 15 was observed closely from a small motorboat west of Tafunsak on 12 October 1981.
The first author (FEH) returned to Kosrae during

NOTES ON GEOGRAPHIC DISTRIBUTION
18-28 June 2013 and, with the second author (BJP), during 17-27 June 2014.Despite several trips by motorboat along the coast while scuba diving, snorkeling, and searching for fruit bats, we observed dolphins only once.On 25 June 2014, a small pod of dolphins approached our small motorboat as we traveled along the northwest coast of Kosrae near Molsron Yela (05.34°N, 162.93°E; datum WGS84), between Okat Harbor and Walung (Fig. 2).FEH obtained a photograph of the dorsal half of a dolphin surfacing beside the boat (Fig. 3).During a snorkeling dive, BJP observed about 10 dolphins before they swam away and obtained a grainy underwater photograph revealing 4 dolphins (Fig. 4).

Results
The dolphins observed on 12 October 1981 possessed uniformly dark backs and whitish sides, which are con-  sistent with S. longirostris.Our photos of the dolphins on 25 June 2014 confirm their identity as S. longirostris based on the extremely long and slender snout combined with the tricolored pattern of a dark gray cape, gray sides, and white belly.The tricolored pattern is typical of the nominate subspecies S. l. longirostris of the western Pacific (present in Micronesia) and the smaller subspecies S. l. roseiventris (restricted to southeast Asia), and differs from the more monochrome gray of the two eastern Pacific subspecies S. l. orientalis and S. l. centroamericana (Perrin 1990, Perrin 2009, Jefferson et al. 1993, Perrin and Gilpatrick 1994, Reeves et al. 2002, Perrin et al. 2007).The lack of spotting distinguishes this species from the Pantropical Spotted Dolphin Stenella attenuata (Gray, 1846) (Jefferson et al. 1993, Reeves et al. 2002), which is widely distributed in Micronesia (Wiles 2005) and has been previously reported from Kosrae (Gilpatrick et al. 1987).The lack of a pale stripe from the eye to the dorsal fin, which would be obvious if present in Figure 3, distinguishes it from the Striped Dolphin Stenella coeruleoalba (Meyen, 1833) (Jefferson et al. 1993, Reeves et al. 2002), which has been recorded elsewhere in Micronesia (Wiles 2005).Other small delphinids recorded from Micronesia (Wiles 2005) include the Rough-toothed Dolphin Steno bredanensis G. Cuvier in Lesson, 1828, which has a similar color pattern but a shorter snout, and the Fraser's Dolphin Lagenodelphis hosei Fraser, 1956, which has a stubby snout and a black lateral stripe (Jefferson et al. 1993, Reeves et al. 2002).

Discussion
Although our observations represent the first confirmed record of S.l.longirostris for Kosrae, we suspect 1 or more small pods routinely visit the coast, which is seldom visited by professional biologists with expertise in identifying marine mammals.Other species of marine mammals reported from Kosrae include the Sperm Whale Physeter macrocephalus Linnaeus, 1758 (Eldredge 1991), S. attenuata (Gilpatrick et al. 1987), Melon-headed Whale Peponocephala electra (Gray, 1846) (Bachman et al. 2014), and Killer Whale Orcinus orca (Linnaeus, 1758) (Iwashita et al. 1963).
Because Kosrae is a small, rugged, and isolated island with a historically low human population density (Gorenflo 1993), its marine environment remains relatively pristine, yet there are many emerging threats to marine ecosystems which, unless mitigated, may adversely affect  marine mammals (George et al. 2008, Wortel 2010).Further observations will undoubtedly add more species to the marine mammal fauna of Kosrae and studies should be undertaken to document patterns of abundance, seasonality, and long-term population trends.

Figure 1 .
Figure 1.Map of Micronesia.Major island groups for which Spinner Dolphin Stenella longirostris longirostris has been recorded (Wiles 2005) are indicated with an asterisk and the new record for Kosrae is circled.

Figure 2 .
Figure 2. Map of Kosrae, Micronesia, with a star indicating the locality of Spinner Dolphins Stenella longirostris longirostris photographed at Molsron Yela on 25 June 2014.