180 U. S. BUREAU OF FISHERIES 
only the smaller rookeries can be accurately counted. Estimates are 
essential for portions of all large rookeries. 
Estimated number of harem and idle bulls, approximate ratio of idle bulls to harem 
bulls, and average harem, 1939 


| Approxi- 












“= aa mate wea 
arem e of idle Average 
Rookery Date | ‘bulls | bulls | Tol | punsto | harem 
harem 
bulls 
St. Paul Island: 
IKGtOMI eee se en ee 458 79 | 537 1:6 47.94 
Lukanin__ 166 38 204 1:4 63.95 
Gorhatch ___ 900 550. 1, 450 1:2 61. 94 
Ardiguen tse 222 Se sees a |e dots 12. 103 20 123 1:5 51. 20 
ROO feb eye rere a Soe see es eee dot. 1, 600 485 2.085 1:3 69. 99 
SivutGhess ee soa See ee ee ae doze=s 400 65 465 1:6 85. 67 
Tagoon tases sree ee ee July 18 iL eco ee Ly are et eee 32. 00 
Tolstolsse ee Se Se ee CEL ee eee July 15 975 192 1, 167 15 67.61 
Zapad niet laa eee See eres: July 18 786 250 1, 036 1:3 80. 60 
MittlesZapadinin a lees ee ee eee eee do = 482 118 600 1:4 67. 00 
ZaApaGnivRee tae see pos ea ee ae do!-=- 76 19 95 1:4 14. 74 
Poloving sss eee SAR SEES E De July 16 420 151 571 1:3 54. 21 
Polovina Clifiste= ae eres pee does 355 141 496 1:3 35. 12 
ite wb Olowin ae eee ee ee eee ee dos 165 66 231 13} 27. 51 
Moro vie see ites os See eee July 17 435 181 616 1:2 18. 76 
Wostochnises 22-2 elas onan Gosees= 1, 800 261 2, 061 127 50. 47 
Motal 2222522 23 2 Se ees | ees 9, 122 2, 616 11, 738 1:3 59. 34 
St. George Island: 
INOrthise = ass eee ae bare aes July 21 640 77 717 1:8 69. 03 
StaravavAr tile eee eee ee July 20 534 68 602 1:9 62. 34 
Zapaanie {Wie oe eee ee ea July 22 212 72 284 1:3 22.16 
Southe: oe eee area ee eee ne ee a dons 139 10 149 1:14 7.94 
MMASt) ROGGE 2 Fee ters Nine NA een en July 21 102 50 152 12 99. 24 
Mast jC liffse2 See Eee ae ee EE deez = 231 80 311 1:3 125. 13 
Motaleesat ho ess Ree Serene Se | LE ye 1, 858 357 2, 215 s5) 65. 82 
Total (both islands). ...----------|---------- 10, 980 | 2,973 | 13,953 1:4 60. 44 

AVERAGE HAREM 
The average harem computed for 1939 was 60.44, compared with 
46.69 in 1938. This estimate is based on an average increase for 
cows of 8 percent. It has been felt for a number of years that an 8 
percent increase may be somewhat too high, and, if this is true, the 
actual average harem would be somewhat smaller than computed. 
The great increase in the average harem this year might indicate, if 
there is no change another season, that killings have been rather close. 
This may not necessarily be true, however, as the proportion of 
3-year-olds remaining during the years from which present harem and 
idle bulls were recruited should have been more than sufficient, under 
normal circumstances, to provide enough bulls for a smaller average 
harem. Sometime during the life cycle of these animals there must 
have been a larger percentage of deaths than normal. It may be that 
as the herd increases, some unknown factor causes an increased death 
rate of all animals. These unknown factors will tend to make it 
considerably harder, as the herd increases, to figure what percentage 
of males it will be necessary to leave for breeding purposes. 
