body weight of the 6-year male is four times 

 that of the yearling female, and since members 

 of the two classes molt at the same time, it 

 may be concluded that season of molt is de- 

 pendent more upon sex than upon body size. 



Females molt later and arrive later on the 

 breeding grounds than do males of the same 

 age. For example, when tagged yearlings were 

 searched for in the period mid-September to 

 mid-November on St. Paul Island, 18 males to 



5 females were found in 1941 and 12 males to 



6 females in 1961. A causal relationship be- 

 tween late molt and late arrival should not be 

 inferred. 



Older seals molt later in autumn; they also 

 may (?) exhibit greater variation in time of 

 molt. Table 7 shows a significant increase in 

 length of the overall molting period with in- 

 crease in age of seal (P< 1 percent). The 

 molting season for 15 yearlings extends over a 

 period of 106 days (3.5 months), and for 58 

 seals older than 10 years over a period of 171 

 days (5.6 months). As previously mentioned 

 (page 9), the findings could mean that in 

 older seals, either molt is more erratic or 

 slower, or both. 



January and June, estimates of the percentage 

 composition of guard hairs as old or new have 

 been made. The estimates are based on larger 

 hairs only — the ones which compose the outer 

 ranks and which can be counted. Smaller hairs 

 are protected by the pelage and some of them 

 remain sharp and unfaded for a year or more. 

 The estimates are unsatisfactory for the fol- 

 lowing reasons: First, they fluctuate widely 

 from one sample to the next, even when the 

 samples represent animals of the same class 

 and season of year. For example, in 13 3-year- 

 olds taken in February 1961, the estimates are 

 (percent old fibers); 5, 10, 15, 15, 25, 35, 35, 

 40, 50, 60, 60, 70, and 80. The wide range is 

 believed to represent, for the most part, poor 

 judgment in identifying old and new hairs. 

 Second, the estimates show no clear relation- 

 ship to age of seal or to month of collection. 



When the data for all samples are combined, 

 however, they suggest that, on the average, 

 about 25 percent of the larger guard hairs of 

 the female between January and June are un- 

 shed hairs of the previous generation. An 

 analysis by month for 225 specimens is given 

 below: 



Jan. Feb. Mar. Apr. May June Total 



PERSISTENCE OF OLD-GENERATION 

 GUARD HAIRS AFTER THE MOLT 



Mean per - 



cent old 



hairs 29.4 



28.3 22.2 20.1 27.2 S.7 24.4 



Evidence from 

 Hair Shafts 



Inspection of the Guard 



From inspection of the pelage fibers in early 

 spring it is apparent that at least two genera- 

 tions (year classes) of guard hairs are present. 

 The older hairs are dull and faded, with tips 

 frayed or broken and with shafts pock-marked 

 or eroded at the edges. The newer hairs are 

 dark brown, with long, slender, glistening, 

 transparent tips and with smooth shafts. The 

 hairs start to deteriorate in March, when a 

 few are slightly faded and their tips are 

 brushy. By May, all show fading, though a few 

 still have sharp tips. By July, all hairs are 

 faded and all tips are moderately to exces- 

 sively frayed. It is now impossible to distin- 

 guish the old from the new generation. 



On the basis of 225 specimens representing 

 female seals older than 1 year, killed between 



Number in 

 s ample 42 



57 55 



47 



16 



8 225 



Evidence from 

 Hair Roots 



Inspection of the Guard 



While the new guard hair fiber is pushing its 

 way upward through the skin and through the 

 old pelage, its course for about a month runs 

 parallel to the resident fiber. The two fibers 

 share a common pilary funnel (skin pore). 

 During active stages of molt, the stumps of 

 many such paired fibers or "twins" show on a 

 horizontal section cut near the surface of the 

 skin (table 8). 



In beginning molt, by definition, the hairs 

 have not yet erupted. Only about 1 percent of 

 the pilosebaceous units near the surface of the 

 skin contain twin hairs. In early and late molt. 



15 



