PREWEANING MORTALITY OF WEDDELL SEAL PUPS

We examined mortality prior to weaning of Weddell seal pups (Lepronych otes weddellii), using resighting data collected from 1984 to 1993 on the annual ice of McMurdo Sound, Antarctica. Mortality rates were esti mated using counts of dead pups found on the surface and mark-recaptur e techniques. The standard Jolly-Seber model for open populations fit the recapture data best and corresponded well to the known biology of these animals. Yearly mortality rates estimated by mark-recapture tech niques ranged from 6 to 22%, with a mean across years of 13%. These va lues are twice as high as those previously reported for Weddell seals and those calculated from counts of dead pups in this study. This sugg ests that there is significant unseen mortality due either to undiscov ered fatalities on the ice surface or to significant mortality occurri ng in the water.