FUR SEALS AND OTHER LIFE, PRIBILOF ISLANDS, I914. 91 



The measurements of the seals of a given age are much more uniform than the size 

 or weight of the skins. The most important measurement and one that is easily taken 

 is the length from the end of the nose to the root of the tail, and the idea was conceived 

 of using this measurement as a standard for judging the age of seals killed. It was 

 found entirely practicable to take this measurement for each one of the seals without 

 delaying the progress of the work as they were laid out in rows preparatory to skin- 

 ning. The most satisfactory method of measuring is by means of calipers similar to those 

 employed in measuring timber. The one used experimentally was made by fitting a 

 fixed and a movable arm to a rod marked for feet and inches. Even with this impro- 

 vised instrument it was found practicable to ascertain the length of the animal easily 

 and quickly. As explained elsewhere, a large number of skulls of seals killed in the 

 food drives were preserved. Some of these were of seals branded as pups in 191 2. 

 These specimens of known age, studied in connection with the flesh measurements and 

 the weight of the fresh skins, serve as a basis for comparison with the older seals. The 

 specimens include also a large series of 3-year-olds and a few older seals. It was thus 

 possible to ascertain the approximate size of the seals of different ages. Owing to the 

 fact that there is a range of nearly two months in the actual ages of the seals of a given 

 class, and because of the range of individual variation, there is a small percentage of 

 animals whose age can not be absolutely determined even by careful examination. A 

 careful study of the data at hand, however, convinces that this proportion is probably 

 not greater than i in 50 and may be regarded as negligible. To show how nmch 

 greater is the variation in the weight of the skins of seals of a given age, compared with 

 the total length, the data regarding a killing of 61 seals made on August 10 may be 

 briefly discussed. These seals were selected with ordinary care by the natives as being 

 3-year-olds. Before they were skinned the length of each animal from the tip of the 

 nose to the base of the tail was taken with calipers and this measurement was recorded 

 against the tag number of the skin. Ten skulls selected at random from the lot were 

 saved for examination. Each skin was then weighed before being salted. 



Of the 61 seals, 56 ranged from 44 to 49K inches in length. Of these, 8 measured 

 44 to 44^ inches; 10, from 45 to 45 K inches; 12, from 46 to 46K inches; 8, from 47 to 

 j,j]A inches; 10, from 48 to 48;^ inches; 8, from 49 to 49K inches. Of the remaining 

 5 seals, I (probably a 2-year-old) measured 41 inches, and the skin though fat weighed 

 only 5 pounds and i ounce; one measured 42 X inches, and 2 measured 43 inches; the 

 remaining one measured 51 inches and since its skull was that of a 3-year-old it doubt- 

 less represents the maximum size for this class. 



Regarding the weight of the skins of the 56 animals ranging in total length from 

 44 to 49>^ inches, every one of which was certainly a 3-year-old, the lightest weighed 

 5 pounds 6% ounces, and the heaviest 9 pounds lo^ ounces. The variation in measure- 

 ments was thus only 1 1 per cent of the maximum, while the variation in the weight of 

 skins was 44 per cent of the maximum. The 12 skins from animals of practically the 

 same length — 46 to 46^^ inches — ranged in weight from 5 pounds 6% ounces to 8 pounds 

 SX ounces. 



An incident showing how little dependence can be placed on the weight of skins 

 as a criterion for age occurred on August 6, when a skin weighing 11 pounds 7^ ounces 

 was noticed to bear an excessive amount of flesh, probably having been skinned by an 

 inexperienced native. After being divested of the superfluous muscle and fat, it was 

 found to weigh 9 pounds 11^ ounces, a difference of i^ pounds. 



