dc.description.abstract | To successfully transition from nursing to foraging, phocid seal pups must develop adequate
diving physiology within the limited time between birth and their first independent foraging trip to
sea. We studied the postpartum development of oxygen stores in gray seals (Halichoerus grypus, n =
40) to better understand the ontogeny of diving capacity in phocids. Hemoglobin (Hb), hematocrit
(Hct), blood volume (BV), and myoglobin (Mb) levels in newborn (3 d postpartum [DPP]) and newly
weaned (DPP) pups were among the lowest 17 +/- 0.4 measured across age classes. During the pups'
terrestrial postweaning fast (PWF), Hb, Hct, mass-specific BV, and Mb increased by 28%, 21%, 13%,
and 29%, respectively, resulting in a 35% increase in total body mass-specific oxygen stores and a
23% increase in calculated aerobic dive limit (CADL). Although Hb and Hct levels at the end of the
PWF were nearly identical to those of yearlings, total body mass-specific oxygen stores and CADL of
weaned pups departing for sea were only 66% - 67% and 32% - 62%, respectively, of those for
yearlings and adult females. The PWF represents an integral component of the physiological
development of diving capacity in phocids; however, newly independent phocids still appear to have
limited diving capabilities at the onset of foraging. | en_US |