Figure 3. --Molt mid-dates; straight line fitted to data 

 from table 6; male. (Y = 250.55 + 3.43 X.) 



Figure 4. --Molt mid-dates; straight line fitted to data 

 from table 6; female. (Y = 264.05 + 5.46 X.) 



a quadratic or logarithmic curve. The present 

 data, however, suggest a linear relationship. 

 Spotty sampling of older animals, especially 

 males in winter, is probably the reason. The 

 mid-dates of molt for some ages have been 

 estimated from both linear and logarithmic 

 equations (table 6). The following conclusions 

 are predicated on a linear relationship: 



The sexes have a similar molt pattern. The 

 molt begins about 20 July in yearling males and 

 reaches the mid-date on 11 September. In year- 

 ling females it begins about 5 August and 

 reaches the mid-date on 27 September, 16 

 days later than the mid-date for males. The 

 estimated mid-date for males is 3.4 days 

 later with each year of age; for females, 5.5 

 days later with each year of age. The rate of 

 change of the mid-date is significantly different 

 for males and females. The difference between 

 the mid-dates for males and females increases 

 by approximately 2 days with each year of age. 



Figures 3 to 6 illustrate these differences 

 between sexes. 



The oldest female fur seal alive is perhaps 

 25-30 years of age. From the first series of 

 tagging experiments in 1941, four 20-year-old 

 females were recovered in 1961. A female 

 identified by tooth-layer counts ab 26 years old 

 was killed at sea in 1959. If the trend of dates 

 of mid-molt is projected to the female of age 

 26, the date of 17 February is reached, a date 

 which is compatible with finding of one old 

 female in beginning molt on 5 January 1961. 



The mid-date of molt for the average 6-year 

 male is 27-28 September, the same as for the 

 yearling female. This means that all males 

 age 5 and younger tend to pass through mid- 

 molt before females of any age. Since the 



Figure 5. --Molt mid-dates; logarithmic curve fitted to 

 data from table 6; male. (Y = 248.41 + 30.27 log X.) 



Figure 6. --Molt mid-dates; logarithmic curve fitted to 

 data from table 6; female.(Y= 245.40+ 75.65 log X.) 



13 



