Sperm whale (Physeter macrocephalus) responses to a fixed-wing aircraft

Smultea, M.A.¹, J.R. Mobley² and D. Fertl³
¹Foster Wheeler Environmental Corp., 12100 NE 195TH St., Suite 200, Bothell, WA 98011
²University of Hawaii - West Oahu, 96-129 Ala Ike, Pearl City, HI 96782
³Geo-Marine, Inc., 550 East 15th St., Plano, TX 75074

Very few data are available on the reactions of cetaceans, particularly sperm whales (Physeter macrocephalus), to aircraft overflights. We describe an obvious behavioral response by a group of 11 sperm whales (including one calf) to a small twin-engine fixed-wing aircraft (Cessna 337G "Skymaster") circling at altitudes of approximately 245 to 335 meters (800 to 1,100 feet). This observation occurred on 9 April 1994, approximately 50 kilometers (30 miles)off the north coast of Kauai where the bottom depth was approximately 4,000 meters (2,200 fathoms). Sperm whales responded to the aircraft by moving closer together and forming a fan-shaped semi-circle with their flukes to the center and their heads facing the perimeter. Several sperm whales in the group were observed to turn on their sides, to apparently look up toward the aircraft.

Based on other reported observations of sperm whale responses to various perceived and assumed potential threats, the behavior of these observed sperm whales is believed to have been a negative response to the aircraft. The sperm whales likely received both visual and acoustic cues from the aircraft. As such, the observation was counted as a non-lethal "take" under the National Marine Fisheries Service (NMFS) Permit No. 810 issued to J.R. Mobley granted for the aerial survey study, and categorized as Level B harassment. The observed reaction is assumed to have been short term, with no long-term adverse effects of biological significance.