
APPENDIX B 
Fecundity of males 
The testes and the reproductive behavior of males have been 
studied with two objectives in mind: (1) the age of sexual maturity, and 
(2) the potency rate among adults. The results are summarized as follows: 
Age of sexual maturity 
1. Smears were made from the testes of 10 known-age 3-year-olds 
collected on 27 July 1950. Dr. Oliver P. Pearson found sperm in four of 
them. Testes weighing less than 30 grams contained no sperm, while those 
weighing 30 grams or over did (letter of 3 October 1950). 
2. Testes from seals in the critical ages 3, 4, and 5 were 
studied and described by Dr. Richard J. Blandau (letter of 29 December 
1950): 
Three~year-old testes, totaling 25 pairs, weighed from 10 to 
74 grams (mean 31.6). "From the survey of the whole 3-year-old group, 
I would conclude that all of the animals with the possible exception of ... 
{the largest, 74 grams] would not be able to reproduce." 
Four-year-old testes, totaling 10 pairs, weighed from 50 to 86 
grams (mean 67.1). Dr. Blandau "would doubt that the 4-year-old seul has 
reached reproductive maturity." 
One pair of 5-year-old testes (91 grams) showed as much 
spermatogenic activity as did the testes of adult bulls. 
3. A study of several mmdred seals ranging in age from pups 
to bulls revealed that testes grow in weight most rapidly in the fourth and 
fifth years, especially the fourth (Scheffer, 1950d, >. 389). 
4 G. Dallas Hanna, studying the branded animals of 1912, saw 
no 6-year, or even 7-year, males on the breeding grounds (U. S. Bureau of 
Fisheries, 1918, p. 126; 1919, p. 114). We have seen a few marked 7~year- 
olds in charge of harems. 
5. Field observations of branded animals clearly demonstrate 
that even a 10-year-old is not as large, nor as active in breeding, as he 
will eventually become. 
Potency 
1. The testes of 11 bulls 10 years of age or older were collected 
at three intervals during the 1951 breeding season. They included 4 pros- 
pective harem bulls collected on the breeding area on 30 June, 4 active ha em 
bulls collected 11-16 July, and 3 idle bulls collected 16-18 July. The tates 
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