The Diet Composition of Beaked Whales and Melon-Headed Whales from the North Pacific

The first component of this overall project involves describing the diet composition of melon-headed whales from the Hawaiian Islands. This report summarizes progress towards this objective. Although melon-headed whales are a poorly-known species, there is more known about melon-headed whales in Hawaiian waters than anywhere else in the world (Aschettino et al. 2012; Woodworth et al. 2012). This species is thought to be sensitive to underwater sounds. In 2004, 150 melon-headed whales demonstrated pre-stranding behavior in Hanalei Bay, Kauai, which coincided temporally and spatially with a RIMPAC (Rim of the Pacific) training exercise (Southall et al. 2006). In 2008 approximately 100 melon-headed whales moved into a shallow water lagoon system in Madagascar, with many subsequently stranding, coincident with the use of a high-power mid-frequency multi-beam echosounder used in mapping offshore of the stranding site. The multi-beam echosounder was thought to be the most likely behavioral trigger for the animals entering the lagoon system (Southall et al. 2013). Despite their distribution throughout the tropics and sub-tropics world-wide, there is no study dedicated to the food habits of this species in the published literature. All that is known of melonheaded whale diet comes from the stomach contents of individual specimens in Hawaii and South Africa and unpublished data from a mass stranding in Brazil (Barros, unpublished, Best and Shaughnessy, 1981; Clarke and Young, 1998; Sekiguchi et al. 1992). An examination of the food habitats of melon-headed whales from any region of the world would be a valuable contribution to furthering our understanding of the foraging behavior of this species. Such an examination of food habits from Hawaiian melon-headed whales would be especially relevant in light of the 2004 mass stranding behavior and the continued importance of Hawaiian waters to naval training exercises.