Meeting Abstract
During the Antarctic summer, female Weddell seals (Leptonychotes weddellii) expend much of their fat and protein stores while nursing. Recovery of these reserves may influence future reproduction. To determine how mass dynamics differ between postpartum (moms, n=64) and non-reproductive seals (skips, n=32), we measured mass and body condition near weaning, in Nov/Dec, and again during the molt in Jan/Feb. Overall, moms were smaller and leaner than skips in Nov/Dec (mean±SE 282.0±4.6 kg, 31.8±0.5% lipid vs. 437.4±6.7 kg, 38.2±0.5% lipid). After weaning, moms gained weight at an average rate of 0.6±0.1kg/day, accruing primarily lean mass. In contrast, during this same period skips lost an average of 1.0±0.1kg/day, mostly as lipid. This indicates that midsummer is a critical period for mass recovery in moms, but for larger skips, foraging is less important. Surprisingly, despite different mass dynamics, all females ended the summer leaner than at the start. In many species mass loss and reduced lipid reserves are associated with elevations in cortisol levels, which in turn can have negative impacts on reproduction and other life history events. Prior work with this species has shown that serum cortisol is elevated in leaner, post-reproductive females in late summer, but these were single time-point measurements. We will measure cortisol in hair that grew between the two handling periods to assess cortisol levels across a longer time frame. Hair cortisol will be compared to body condition and mass flux, and preliminary results suggest levels are higher in moms than skips. Links between body stores and hair cortisol levels in reproducing and non-reproducing female Weddell seals may indicate physiological trade-offs associated with pupping.
