Table 31. --Rate at which territories were re-established in 

 areas where territorial male seals were killed, St. Paul, 

 1965 



1/ All areas were not observed every day. 



of annual mortality of 0.36 calculated by 

 Chapman (1964) from the age composition of 

 males 7 years old and older in pelagic re- 

 search collections. Peterson concluded from 

 observations of 18 tagged and marked ter- 

 ritorial males that annual mortality was 0.33. 

 Because the estimates are similar and be- 

 cause there is not a good basis for making a 

 correction, we conclude that the estimate of 

 0.38 calculated from the data presented here 

 represents annual mortality. 



Replacement of Territorial Males 



One hundred territorial males were killed 

 18-25 June on two areas of Northeast Point 

 Rookery and rennoved. The territories of these 

 males were quickly reoccupied (table 31); 

 within 24 hours more than 50 percent of the 

 original number of territorial males had been 

 replaced. Occasionally, a male tried to occupy 

 a territory within 2 or 3 minutes after the 

 original holder had been killed and before the 

 data had been collected from the dead aninnal. 

 Thirty-five of fifty-two males killed on North- 

 east Point Rookery were removed between 

 9 a.m. and noon. By noon, 13 males had 

 moved into this area. This number had in- 

 creased to 17 by 4 p.m. and to 26 by 8 p.m. 



Richard S. Peterson. 1965. Behavior of the northern 

 fur seal. The Johns Hopkins Univ., Baltimore, Md., D.Sc. 

 thesis, 12 + 214 pp. 



The areas appeared completely reoccupied 

 by about the 6th day after the original ter- 

 ritorial males were killed. Beginning at the 

 edge of the water, replacement males estab- 

 lished territories progressively farther inland. 

 Although most of the replacement males ap- 

 parently came from the water, their real 

 origin could not be determined. 



The age compositions were similar for 50 

 territorial males killed 5-8 July on Sea Lion 

 Rock, and their 50 replacements taken 15 July 

 (table 30). 



The high mortality of adult males and the 

 short time that elapsed before territories 

 were reoccupied indicate that the rate of 

 utilization of males can be increased without 

 adversely affecting reproduction. 



Measurements of Territorial Males 



Body length and the weights of the baculum, 

 body, and paired testes were taken from the 

 territorial males killed in 1965, though all 

 four measurements were not recorded for 

 each. Weights of the testes and bacula were 

 taken for nearly all of the males, whereas 

 body length and weight were recorded only for 

 those killed in June (table 32). The means for 

 body length and weight are probably slightly 

 less than they would have been if the animals 

 had not lost blood before they were weighed 

 and if it had been possible to place the animals 

 on a flat surface before length was measured. 



The testes of territorial males taken 5-10 

 July were significantly heavier (P<0.001) than 

 those from males collected 18-23 June-- 

 126.4 g. compared to 113.2 g. Fifty males 

 occupying the territories of males killed 

 5-8 July were taken on 15 July. Their testes, 

 which averaged 122.6 g., were significantly 

 heavier (P<0.05) than the testes of males 

 taken in late June, though they were not 

 significantly different from those of territorial 

 males killed in July. The greater weight of 

 the testes in early July probably reflects an 

 increase in breeding activity. 



Body length and weights of the baculum, 

 testes, and body showed no relation to age 

 (figs. 17, 18, 19, and 20), nor was there a 

 relation between weights of the baculum and 

 testes (fig. 21). There was, however, a slight 

 indication of a positive correlation between 

 body length and baculum weight (fig. 22). 



Table 32. --Means and ranges of measurements of territorial 

 male i.eals, St. Paul Island, 1965 



Measurement 



Range 



Number 



Body length 197.1 cm. 168-21'C 36 



Body weight 190.8 kg. 138.9-237.-4 99 



Testes weight (pair)... ^ 120.3 g. 6';-199 248 



Baculum weight 9.4 g. 5.7-16.1 250 



'^ The weights of testes taken in Juljr were significantly 

 heavier than those in June, 125.1 compared to 113.2 (see 

 text). 



32 



I 



