Satellite Tracking of Migrating Humpback Whales in Hawaii

This report describes our teams research conducted to better understand the behavior of humpback whales (Megaptera novaeangliae) in the deeper waters of their Hawaiian breeding grounds west of Kauai, near the Pacific Missile Range Facility. Seven presumed males were satellite tagged using LIMPET-configured SPLASH tags in late March 2017. All tagged whales were traveling away from Kauai when encountered, heading west towards the island of Niihau, which they circled for 1.07.9 days. Five whales continued to travel west/northwest, with directed travel over deep water while milling over shallow seamounts. Four of the tags stopped transmitting while the whales were at or near these seamounts. Only one whale traveled directly north from Niihau rather than following the Hawaiian archipelago to the northwest. Tags remained attached for 1.612.3 days, and total distances traveled ranged between 143.5 and 826.4 km, although straight-line distances traveled were far shorter (19.8548.8 km). The median travel speed while near islands or seamounts was 1.1 km/hr, while the median intermediary speed approaching or leaving these areas was 3.0 km/hr, and the median directed travel speed over open water was 5.5 km/hr. Mean dive depth was 33.4 m, while maximum dive depths reached 395.5 m. Dive depths correlated with seafloor depths, with dives over shallow seamounts often using the full extent of the water column, while the deepest dives occurred over open water and usually at night. These results begin to provide insight into the offshore and migratory behavior of humpback whales in Hawaii, and build a baseline of behavior against which to compare potential responses to Navy training activity in this area.