of a bachelor seal and was about to photograph them when he 

 noticed four ridges on the root of each large tooth. Could 

 these correspond to the age of the seal in years? Upon exami- 

 nation of known-age teeth, the answer was "probably." A 

 visit was made to a refuse heap where, a year earlier (15 July 

 1948), the carcasses of the Reef kill had been dumped. From 

 the teeth of 178 skulls, the composition of the kill was esti- 

 mated to be: 2-yr-olds, 2%; 3-yr-olds, 68%; 4-yr-olds, 29%; 

 and 5-yr-olds, 1%. This posthumous evidence supported a 

 hunch that 4-yr-olds were contributing substantially to the an- 

 nual kill. Annual ridges up to about the sixth can be counted 

 on the surface of the seal's tooth. In the late 1950's, biologists 

 Abegglen, Fiscus, Roppel, and Wilke perfected a sectioning 

 technique by means of which at least 26 annual layers can be 

 counted (Fig. 10). 



The age composition of an annual kill as determined by 

 tooth-ridge counts was first published for the St. Paul season 

 of 1950 (Kenyon et al. 1954:17). It was first published in rou- 

 tine reports of the fur seal industry for the season of 1954 

 (Thompson 1956:64). In a parallel table, Thompson gave the 

 age composition as estimated from body lengths. The two 



tables were quite different, the teeth indicating a 3-yr-old kill 

 of 64%, the lengths, 90%. Reporting of the annual kill by 

 body length was discontinued with the season of 1956. 



It was becoming clear that the tables compiled by Hanna in 

 1913-20, showing the relationship between age and body 

 length of male seals, could no longer be used to estimate age. 

 Scheffer (1955) concluded that in the three decades since Han- 

 na's time, while the seal population had increased 4.3 times, 

 the average size of the individual had decreased as a result of 

 what we may call "crowding." He compared the branded, 

 known-age seals of Hanna's time and the branded or tagged 

 seals of the period 1941-52 with respect to body weight, field 

 length, skull length, and skull width (Fig. 11). "Of fifteen 

 comparisons based upon four age groups (three to six years) 

 and four measurements . . . nine point to a significant de- 

 crease in mean body size at the 1 percent level and three at the 

 5 percent level. For three comparisons, the differences are not 

 significant" (Scheffer 1955:499). Nagasaki (1961:29-33) car- 

 ried the study further, comparing body size of Pribilof seals in 

 1952 with that in 1958-62. A downward trend in size was ap- 

 parently continuing. 



Figure 10. — Top: Ancel M. Johnson removing the snout of a female seal for age 

 estimation from the teeth, St. Paul Island, 8 August 1961 (photo by V. B. 

 Scheffer). Bottom: Stanley B. Phillips grinding seal teeth, preparing to estimate 

 age from growth-lines in the roots, 7 October 1963 (Photo by V. B. Scheffer). 



Figure 11. — Top: Aleut foreman John Hanson measuring a seal on Reef killing 

 field, 25 July 1946. Measuring was discontinued at the end of 1961 (photo by 

 V. B. Scheffer). Bottom: Weighing a known age (tagged) 9-yr-old male seal on 

 the Reef, weight 415 lb, 1 July 1949. Left to right: Robert Dickerman and Karl 

 W. Kenyon (photo by V. B. Scheffer). 



34 



