Behavior Of Summering Gray Whales
Abstract: This study quantifies basic dive characteristics and behaviour patterns of undisturbed gray whales (Eschrichtius robustus) observed summering at four northern California locations: the Big Lagoon-Patrick's Point area, Orick, Klamath River mouth, and Crescent City. Observable behaviours were limited to several locomotions (swim slow, swim moderate, swim fast, and floating) seen in different behavioural contexts (milling, circling, pluming, and transit). Sixteen behaviours were observed and they fit naturally into locomotive-context categories (i.e., swim-milling, swim slow - circling, etc.). Each behaviour was described using behavioural observations and dive characteristics. Behaviours that did not appear goal oriented or directed, i.e., milling and floating, had highly variable dive characteristics. More specific behaviours, such as'circling and pluming, were less variable. Some specific and less directed behaviours appeared functionally related and usually occurred together. Apparent bottom feeding was observed and the Big Lagoon - Patrick's Point area appeared to be a favoured feeding site, as evidenced by mud plumes and repetitive circling of surfacing animals. Feeding was composed of at least three observable behaviours: circling, circling with pluming, and milling with pluming. Locomotive-context categories are useful in refining broad behavioural definitions and quantifying basic behaviour patterns. This approach can enhance the interpretation of observable surface behaviours.
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