TAG-SHEDDING FROM SOUTH-AFRICAN FUR SEALS ARCTOCEPHALUS-PUSILLUS-PUSILLUS

Rates of tag-shedding are determined for monel-metal tags applied to f ore-flippers of 21 799 pups of the South African fur seal Arctocephalu s pusillus pusillus in 12 colonies in the years 1971 and 1973-1979. Ha lf of the pups (alternate ones) were tagged on both fore-flippers. The major aim of the study was to estimate pup population size by mark-re capture. Collection on tags from pups killed in harvests 5-9 months af ter tagging permitted rates of tag-shedding to be determined. For 10 d ifferent taggers, this averaged 0,149 (SE 0,0053), and ranged from 0,0 68 to 0,338 for individual taggers. Because it is easier to apply a ta g to one fore-flipper than the other, the rates of tag-shedding are li kely to be inflated over what they would be if all pups were given a s ingle tag applied to the flipper of choice. The variation between tagg ers indicates that greater efforts should be made to standardize taggi ng procedures. The average rate of tag-shedding was similar to that re ported for Weddell seals Leptonychotes weddellii in their first year a nd for young northern fur seals Callorhinus ursinus (although age-clas ses and time periods for the latter species were different). The high rate of tag-shedding within the first year of life highlights the need to include this parameter when estimating survival rates based on tag ged animals.