be a result of the heavy sighting effort 

 inshore in 1972 during the times of 

 the northern migration. The few sight- 

 ings of mothers with calves late in 

 the season, however, were more off- 

 shore. 



Of the 23 times mothers with calves 

 have been observed, in 18 mothers 

 and calves have been either by them- 

 selves or with other mothers with 

 calves. In only four instances were 

 they in the company of other adults. 

 This observation may be supported 

 in part by the fact that females with 

 calves are not receptive to breeding 

 because a female calves and breeds in 

 alternate years (Scammon. 1874; Gil- 

 more. 1961; Rice and Wolman. 1971). 



Yearlings 



There is still little information in 

 the literature on the distribution and 

 movements of yearling gray whales. 

 Hubbs (1972 pers. comm.) has ob- 

 served solitary yearlings migrating 

 south very near shore off La Jolla. 

 Gilmore (1960b) reported that year- 

 lings frequently travel with larger 

 adult animals on the southern migra- 

 tion, presumably learning the migra- 

 tion route, but that solitary individuals 

 are also seen. 



Based on the growth curve of gray 

 whales (Rice and Wolman. 1971) and 

 on estimates of size range at time of 

 weaning (Gilmore, 1961). all whales 

 estimated in our surveys to be be- 

 tween about 6 and 9 meters (20-30 

 feet) long were classified as yearling 

 whales. The opportunity to observe 

 Gigi (8.26 m |27 ft] long) from the 

 air for nearly an hour in early March 

 1972 verilied the accuracy of my 

 previous size estimates and increased 

 confidence in the reliability of the 

 classification in subsequent sightings. 



The room for error in this estimate 

 notwithstanding, yearling-sized whales 

 were observed with higher frequency 

 than expected (Figure 7). A total of 

 21 yearlings or groups of yearlings 

 was observed in the study area. Of 

 those. 16 were observed after the re- 

 lease of Gigi (Evans. 1972) all during 



Figure 6. — Locations of 

 sightings of mottier-calf 

 groups during aerial sur- 

 veys. 1969-72. 



Figure 7. — Locations o( 

 sightings ot probable year- 

 ling gray whales (estimat- 

 ed size. 20 to 30 feet) dur- 

 ing aerial surveys, 1969-72. 



34° 



33° 



32° 



120° 



the period of the northward migration. 

 No yearlings were seen south of the 

 Coronado Islands, but a total of 16 

 was encountered on a 2-day surve\ 

 flight north to Monterey Bay in April. 

 All were within 5 km of the beach. 

 No yearlings were observed in the 

 offshore areas where other whales 

 were seen. Further, like cows and 

 calves, yearlings tended to be either 

 by themselves or with other yearlings. 

 In only 4 of the 2 I cases were year- 

 lings accompanying adult animals. 

 This absence of yearlings with adults 

 may be a result of the forced rejection 



119° 



118° 



117° 



h\ the mother at the lute summer 

 weaning in the north. 



Rates of Movement 



Estimates of rates of movement for 

 southward migrating whales have 

 ranged from 7.7 km/hour calculated 

 over the entire migration route (Pike. 

 1962) to 10.2 km/hour calculated 

 over a small segment of the route 

 (Cummings et al.. 1968). Rice and 

 Wolman (1971) used ihe times of peak 

 passage at two separate shore stations 

 to calculate the average distance trav- 



48 



