Humpback whale Megaptera novaeangliae song reveals wintering activity in the Northwestern Hawaiian Islands

Abstract

The main Hawaiian Islands (MHI) are the principal breeding ground for humpback whales in the North Pacific. Over the past 3 decades, population recovery from whaling-era losses has resulted in a steady increase in the number of whales wintering in Hawaiian waters and a geographic expansion of their distribution in the MHI. Until recently, no existing evidence showed that this expansion included the islands, atolls, and banks of the Northwestern Hawaiian Islands (NWHI). To better understand the occurrence of humpback whales in the NWHI, 9 ecological acoustic recorders (EARs) were deployed at sites throughout the archipelago to record the occurrence of humpback whale song, an indicator of winter breeding activity. Song was found to be prevalent at Maro Reef, Lisianski Island, and French Frigate Shoals but was also recorded at Kure Atoll, Midway Atoll, and Pearl and Hermes Atoll. Both the timing and abundance of song at several locations closely followed trends observed on Oahu, which is one of the MHI, strongly suggesting that humpback whales use the NWHI as a wintering area. This finding is of particular relevance in light of recent suggestions that, based on photo-identification data, a yet undocumented wintering area exists somewhere in the central North Pacific. We propose that the NWHI could be that area.

Humpback whale (Megaptera novaeangliae) song occurrence at American Samoa in long-term passive acoustic recordings, 2008–2009

“…The proportions of days with song within the singing season at Rose Atoll (excluding the single day in June) and Tutuila were 84 and 89%, respectively (Table I); these percentages are comparable to the proportion of days with song reported for west O'ahu (85%; Lammers et al, 2011). In addition, although the Tutuila EAR ceased recording before the presumed peak in humpback whale abundance, the proportion of recordings with song in August at Tutuila (44%; Fig.…”

“…The incidence of song in American Samoan waters was comparable to the incidence of song near O'ahu, one of the main Hawaiian islands, which comprise a well-known wintering area for North Pacific humpback whales (Lammers et al, 2011). The proportions of days with song within the singing season at Rose Atoll (excluding the single day in June) and Tutuila were 84 and 89%, respectively (Table I); these percentages are comparable to the proportion of days with song reported for west O'ahu (85%; Lammers et al, 2011).…”

“…In addition, although the Tutuila EAR ceased recording before the presumed peak in humpback whale abundance, the proportion of recordings with song in August at Tutuila (44%; Fig. 2) approaches the proportion of recordings with song during the peak month of April at O'ahu (53%; Lammers et al, 2011). Although the two regions showed similar proportions of days with song, the number of humpback whales estimated to winter in the main Hawaiian Islands is more than 10 000 animals (Calambokidis et al, 2008), which is more than twice as many whales as are estimated to winter throughout the entire eastern Oceania region (3,827;Baker et al, 2006).…”

“…Humpback song, therefore, is a reliable indication of whale presence and has been used to investigate seasonal occurrence and provide evidence for wintering grounds in other areas (Lammers et al, 2011). Research on humpback whale song in Oceania to date has been based primarily on short-term hydrophone recordings during the seasonal peak in whale abundance, most often from small boats (e.g., Helweg et al, 1998;SPWRC, 2009) or temporarily moored hydrophone arrays (e.g., Dunlop et al, 2007;Noad and Cato, 2001).…”

Effects of Sex, Seasonal Period, and Sea State on Calf Behavior in Hawaiian Humpback Whales (Megaptera novaeangliae)

“…Population numbers in the North Pacific are estimated at 19,594 (Calambokidis et al, 2008), with the Hawaiian population at 10,103 throughout the main islands, 10% of which are calves (Smultea, 1994;Mobley et al, 1999;Calambokidis et al, 2008;Allen & Angliss, 2010). Distribution of humpback whales includes all main Hawaiian Islands (Baker & Herman, 1981), as well as the northwestern islands (Lammers et al, 2011), with the largest numbers occurring off the four-island area of Kaho'olawe, Moloka'i, Lana'i, andMaui (Mobley et al, 1994, 1999).…”