Evidence of Large Whale Socio-Sexual Behavior in the New York Bight

Abstract

Large whales, including the endangered sei whale (Balaenoptera borealis), sperm whale (Physeter macrocephalus), and North Atlantic right whale (Eubalaena glacialis), are known to occur in the New York Bight. However, relatively little data exist on social behavior typical of these species in the area. The U.S. Mid-Atlantic has traditionally been considered a large whale migratory corridor with few surveys documenting social dynamics of whale presence in these waters. To better understand the occurrence, distribution, abundance, and behavior of these species for management and conservation planning, monthly line-transect aerial surveys were conducted over a 3-year period from March 2017 to February 2020. During these surveys, three noteworthy socio-sexual behavior events were observed and photographed within groups of sei whales (April 2019), sperm whales (September 2019), and right whales (December 2019). Events included what could be either non-reproductive sexual behavior (socio-sexual behavior) or sexual behavior (copulation) among conspecifics, including mirror pair swimming, lateral and vertical presenting, and belly to belly contact. During all three events, groups were highly active at the surface, frequently and quickly changing speed and direction, and animals were predominantly less than one body length apart from other conspecifics in the group. All species were recorded rolling onto their sides and/or back while at or near the surface. Open mouth display occurred in the North Atlantic right whale event. Though copulation is unlikely to have transpired during the sperm whale event and could not have occurred during the right whale event due to the identification of same-sex individuals, it cannot be ruled out as the impetus for the sei whale event. These observations begin to describe the relative importance of the New York Bight as more than a migratory corridor and suggest that additional behaviorally focused data collection be incorporated into future surveys.