Social behavior and ecology of "southern resident" killer whales (Orcinus orca)

Abstract

The purpose of the current study was to examine factors that influence social behavior and behavior states in "southern resident" killer whales. Analyses of social behavior indicated that synchronous surfacing between whales was significantly affected by sockeye salmon, with less synchronous surfacing occurring when sockeye were more abundant, suggesting that when whales were foraging, they were spending less time swimming and breathing in synchrony. Furthermore, cartwheels and breaches were significantly affected by time of day, with more of these behaviors seen during mid-day, presumably because human activities are often at their peak during those hours, and whales may be using these behaviors as a warning signal to conspecifics or vessels. Physical contact and spyhops were found to be significantly affected by commercial vessels, as these behaviors increased in the presence of intensifying commercial vessel abundance. As spyhops and contact were posited to be information gathering and subsequent reassurance behaviors, commercial vessels may present a perceived threat to these animals in terms of both noise and size, and whales may therefore produce a higher quantity of these behaviors in their presence. In addition, analyses of behavior states indicated a significant relationship between year and slow travel, with significantly more slow travel seen in 2003 than in 2004 or 2005. Fast travel was found to be significantly different for J pod than for K and L pods, with J pod engaging in fast travel more often than the other two pods. As J pod is more often seen in this region of Washington, it was suggested that habitat familiarity may affect the speed with which J pod transits through the area. Furthermore, a significant relationship between pod and rest was also documented, with K pod found to engage in more resting behavior than J and L pods. In conclusion, complex subtleties emerged from this analysis indicating that killer whale social behaviors are indeed affected not only by multiple ecological variables including salmon abundance and the presence of commercial vessel traffic, but that some of these behaviors vary significantly among pod, time of day, and year.