Spatio-temporal variation and seasonality of Odontocetes' foraging activity in the leeward side of the island of Hawaii

Abstract

The Kona coast of the island of Hawaii hosts many species of odontocetes. These marine mammals are top predators and their foraging activity plays an important role in the ecosystem dynamics. Three passive acoustics recorders were used to study the temporal and spatial occurrence of the foraging activity of odontocetes (excluding beaked and sperm whales) at three locations along the Kona coast of Hawaii between 2012 and 2013. Echolocation clicks were detected using the M3R11M3R: Marine Mammal Monitoring on Navy Ranges; EAR: Ecological Acoustic Recorder; NK: North Kona; CK: Central Kona; SK: South Kona; CS-SVM: Class Specific Support Vector Machine; GLM: Generalized Linear Model; ANOVA: Analysis of variance. (Marine Mammal Monitoring on Navy Ranges) system, and custom-designed Matlab (MathWorks, Natick, MA, USA) programs were designed to analyze the detected data. A Generalized Linear Model was used to understand the influence of location and month on the foraging activity. Both location and month affected the foraging activity of Odontocetes in Hawaii. In general, the foraging activity was the highest in the north and the lowest in the south part of the study area. The model revealed that, at each location, the foraging activity tended to decrease over the time of the study. A seasonality seems to be seen for the two southernmost locations. At the northernmost location the foraging activity decreased from February 2012 till 11 months later (January 2013). Odontocetes daily foraging activity was higher at night-time at all locations sampled.