Observations of Humpback Whales, Megaptera novaeangliae, in the Beaufort Sea, Alaska

Abstract

Humpback Whales, Megaptera novaeangliae, are found in all of the world’s oceans (Reeves and others 2002). Humpback Whales, however, have generally not been found in the Arctic Ocean with the exception of the Barents Sea where warmer waters from the North Atlantic Drift provide rich nutrients for food resources, and ice free zones in the summer (Zabavnikov and others 2005). In the North Pacific, Asian stocks of Humpback Whales summer in the eastern Bering Sea, with some individuals occasionally entering the Arctic Ocean via the Bering Strait and summering along the Siberian coast of the Chukchi Sea (Tomilin 1937; Sleptsov 1961; Johnson and Wolman 1984; Angliss and Allen 2008). Further penetration into the Arctic Ocean, especially into the Beaufort Sea, has probably been prevented by the whales’ natural avoidance of colder waters and associated polar pack ice (Chittleborough 1965; Dawbin 1966). We report on the 1st confirmed sighting of Humpback Whales for the Beaufort Sea, Alaska. During August 2007, FEX LP contracted Agvik Marine LLC to barge oil drilling equipment from Cape Simpson to West Dock (Prudhoe Bay), Alaska, as part of a demobilization of onshore drilling activities conducted the previous 2 winters. On 1 August 2007, at UTM 454911E, 7879755N (WGS84) (about 87 km east of Point Barrow), KAH observed a whale at about 250 m from the barge, and initially identified the individual as a Humpback Whale based on the unique characteristics of the dorsal fin and flukes, and characteristic arching back. Five minutes later the same whale (presumably) approached to within about 75 m of the barge where it was photographed (Fig. 1) and confirmed by BA, an experienced Inupiat hunter, to be a Humpback Whale. During this close encounter, the whale turned on its side revealing the characteristic long pectoral flipper. At this time KAH and the barge’s captain observed a calf with the adult whale. The adult was last seen about 3 min later about 175 m from the barge, slowly traveling to the east. No photographs were taken of the calf or the undersides of the adult’s flukes. At the time of the encounter, the sea state was a Beaufort 3 (large wavelets with occasional whitecaps), the wind was from the east at 10 knots (about 19 km/hr), and visibility was excellent. The barge, hampered by the loss of an outboard engine, was reduced to traveling at ,6 km/hr. Other than approaching the barge, the whales showed no undue reaction to the vessel. Although adult whales were sighted at 3 locations during an 8-min period, we could not positively ascertain whether more than 1 adult whale was present. We believe that we observed only a single cow/calf pair, although it was possible some of the sightings were of an additional Humpback Whale. Further, 2 Gray Whales (Eschrichtius robustus) were observed minutes before the 1st Humpback Whale sighting. While an extralimital sighting of a Humpback Whale in the Beaufort Sea is unusual in itself, the presence of a calf is particularly noteworthy. Based on limited understanding of whales in the North Pacific, it is possible that the whales we observed were part of the Western North Pacific stock that breeds in Asian waters, especially near the Mariana, Ryukyu, and Bonin islands, and summers in the Bering Sea; although the Central North Pacific stock, which breeds among the Hawaiian Islands (Angliss and Allen 2008), may also summer in portions of the Bering Sea. Regardless of origin (Asia or NORTHWESTERN NATURALIST 90:160–162 AUTUMN 2009 160 NORTHWESTERN NATURALIST 90(2)