Little is known about movement patterns and spatial use of pelagic cetaceans in the western North Atlantic. To improve our understanding of these parameters in short-finned pilot whales (Globicephala macrorhynchus), we deployed 48 satellite-linked tags off Cape Hatteras, North Carolina and Jacksonville, Florida from 2014 to 2016. The tags transmitted up to 350 days (mean=70±57 SD) with an average of nine positions per day. Animals tagged off Cape Hatteras (n=44) ranged from North Carolina to Canada and demonstrated a strong affinity for the continental shelf break, although some (n=10) individuals did use pelagic waters. Pilot whales tagged off northern Florida (n=4) showed a more pelagic pattern of spatial use, ranging east of the continental shelf and over the Blake Plateau. We fit Bayesian switching state-space models using 6-hour time steps to 42 suitable tracks to differentiate between two behavioral modes: area restricted-search (ARS, b>1.5) and transit (b < 1 .5). Animals tagged off Florida spent more time (0.61±0.04) in transit mode than animals tagged off Cape Hatteras (0.13±0.01). Almost all (96%) predicted locations within 5km of the continental shelf break (200m isobath) at both locations were consistent with ARS, reflecting the importance of this habitat type to foraging pilot whales. Our results demonstrate that pilot whales are capable of at least two modes of foraging behavior: one taking advantage of fixed bathymetric features, including canyons and areas of high relief, along the shelf break; and a second exploiting more ephemeral oceanographic features associated with frontal systems in the pelagic realm. The importance of these two modes varied with area, although some individuals switched between both patterns.
Citation:
Foley, H., D. Anderson, R. Baird, Z. Swaim, D. Waples, D. Webster, J. Bell, A. Read. 2017. Short-finned pilot whales exhibit two modes of foraging behavior along the East Coast of the United States. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.