In the Magdalena area, courting groups 

 are confined mainly to the outer waters, 

 and cows with calves to inner waters. 



Inner Nursery Area 



Most cows with calves retreat far 

 into the lagoon, although sonne occupy 

 the area in and around the entrance. 

 Cows and their calves gather in great 

 numbers in Laguna Scammon, 20 to 30 

 miles from the entrance. Some court- 

 ing pairs and a few trios may also 

 be seen here in the upper end. A cow 



and her calf are rarely seen with 

 other whales. No cow with calf was 

 seen engaged in mating, although on 

 two occasions a cow with calf was seen 

 swimming in company with another 

 adult. 



The count of whales during a trav- 

 erse of the three areas in Laguna 

 Scammon on January 25 and 26, 1956, 

 gives a quantitative idea of the distri- 

 bution of the groups. A total for the 

 entire 15 -day trip would be misleading 

 because the length of time spent in 

 the three areas differed (table 2), 



TABLE 2.— FREQUENCY DISTRIBUTION OF GROUP SIZE OF GRAY WHALES ON BREEDING GROUNDS 



Composition of group 



Single adult . . . 



Two adults 



Three adults . . . 

 Cow with calf. . 

 Cow-calf -adult . 

 Four or more . . . 



1 (coast) 



REPRODUCTION AND MORTALITY 



REPRODUCTION 



Pregnant female gray whales taken 

 by the Vega (Risting, 1928) ranged 

 from 34 to 50 feet in length; mean 

 length of 23 such females was 37.3 

 feet. The maximum of 50 feet is 5 

 feet longer than given in other rec- 

 ords. Cows with newborn calves do 

 not engage in courtship activity. Evi- 

 dently, therefore, recently parturient 

 cows are not in estrus, and likely do 

 not come into estrus until the following 

 winter, after the calf has been weaned. 

 Reproduction may thus be biennial. If 

 so, it would follow that some females 

 each year bear young and nurse while 

 the others mate. Since copulation and 



parturition are observed at the same 

 time of year, the gestation period must 

 be 11 to 12 months. Two females 

 killed on March 13 and 14, 1912, at 

 Chan Chien Dogo, Korea, each con- 

 tained a fetus, one 7 and one 10 inches 

 long. Nearly grown fetuses found in 

 females at Magdalena Bay were re- 

 ported by Risting (1928) as 16 to 17 

 feet long. These fetuses seem im- 

 probably long. The observed number 

 of new offspring with an adult was 

 always one. 



MORTALITY 



Mortality is thought to be high in 

 the newborn class but not in any other 



18 



