Aspects of the behaviour and ecology of Vancouver Island gray whales, Eschrictius glaucus Cope
Date
1977
Authors
Darling, James David
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This study examines selected aspects of the behaviour and ecology of gray whales, Eschrictius glaucus, especially of summer residents along the west coast of Vancouver Island. Work was centered on Wickaninnish Bay and adjacent waters from March, 1975 to October, 1976 with most observations during March to October each year. The northward migration of gray whales from the Baja calving lagoons lasts from mid-February until mid-June -peaking in early April. During the spring migrations whales closely followed the Vancouver Island coast. The southward migration passes Vancouver Island from late November until mid-January. Whales present in the summer between the north and south movements were considered to be residents. During some winters whales are also resident between periods of annual movement. Many individuals were identified by photographs of skin pigmentation patterns. At least 65% of the 1975 summer residents returned in 1976. Some individuals have been sighted in the study area for 5 and 6 successive summers. Estimates of summer resident populations were 26 in 1975, 34 in 1976 and 42 over both summers (9 seen only in 1975, 17 in both years and 16 only in 1976). Variation was probably due to the home range of summer residents being larger than the study area. Movements during the summer were associated with travel, between feeding areas, to a tide-rip sand bar area and in and out of the study area. In both 1975 and 1976 resident whales were scarce in late July and early August. Length measurements of three individuals, using aerial photogrammetry techniques, suggested that the summer population includes adults, juveniles and young of the year, apparently recently weaned. Previously described feeding behaviour, a method unique to gray whales whereby sand and associated infauna are sucked into one side of the mouth and subsequently separated by forcing the water and sand out through baleen plates, was observed many times. In parts of the study area examined the dominant component of the benthos was a polychaete tubeworm Onuphis elegans. Other behaviours included rubbing on a sand bar in a tide-rip area, resting and a variety of social interactions including paired swimming and homosexual behaviour.