PHYSIOLOGICAL AND BEHAVIORAL DETERMINANTS OF THE AEROBIC DIVE LIMIT IN WEDDELL SEAL (LEPTONYCHOTES WEDDELLII) PUPS

The aerobic dive limit, as defined by an increase in plasma lactate le vels following dives, has to date only been determined in adult and ju venile Weddell seals (Leptonychotes weddellii). However, theoretical a erobic dive limits based on calculated total body oxygen stores, estim ated metabolic rates, and dive duration frequencies have been publishe d for several species. Using data collected over the past 3 years in M cMurdo Sound, Antarctica, the aerobic dive limit of Weddell seal pups was determined by both the physiological and modeling methods. Time-de pth diving recorders deployed on 36 pups between 2 and 14 weeks of age allowed the aerobic dive limit to be predicted from duration-frequenc y histograms. The aerobic dive limit was also calculated from estimate s of total body oxygen stores and predicted diving metabolic rates. Fi nally, these two estimates were compared with aerobic dive limits dete rmined from post-dive lactate levels in three pups between 5 and 7 wee ks old. The aerobic dive limit of pups increased with age, but pup aer obic dive limits were still significantly shorter than those of yearli ngs and adults. In addition, the aerobic dive limits determined by the three methods were not equivalent for pups, yearlings, or adults, and indicate that care should be taken when modeling methods are used to estimate the aerobic dive limit in other species. Changes in hematocri t, plasma glucose, and plasma lactate levels during and between rest, diving, and recovery in pups were compared to known values for juvenil es and adults. Plasma metabolite levels were more highly regulated in older pups, and together with the increasing aerobic dive limit, sugge st that Weddell seal pups are not refined divers until after they are weaned, and that their diving ability continues to develop over severa l years.