Migratory carryover effects and endocrinological correlates of reproductive decisions and reproductive success in female albatrosses
Physiological mechanisms mediating carryover effects, wherein events or activities occurring in one season,
habitat, or life-history stage affect important processes in subsequent life-history stages, are largely
unknown. The mechanism most commonly invoked to explain carryover effects from migration centres
on the acquisition and utilization of resources (e.g. body mass, or individual ‘condition’). However, other
mechanisms are plausible, e.g. trade-offs reflecting conflict or incompatibility between physiological regulatory
systems required for different activities or life-history stages (migration vs. reproduction). Here
we show that in female black-browed albatrosses (Thalassarche melanophris) the decision to reproduce
or to defer reproduction, made prior to their arrival at breeding colonies after long-distance migration,
is associated with condition-related (body mass, hematocrit, hemoglobin concentrations) and hormonal
(progesterone, testosterone, estrogen-dependent yolk precursors) traits. In contrast, reproductive success
showed little association with condition but showed significant associations with the steroidogenic processes
underlying follicle development. Specifically, success was determined by reproductive readiness via differences in steroid hormones and hormone-dependent traits. Successful albatrosses were characterized by high progesterone and high estradiol-dependent yolk precursor levels, whereas failed albatrosses had high testosterone and low yolk precursor levels. Results are discussed with reference to
migratory carryover effects and how these can differentially affect the physiologies influencing reproductive decisions and reproductive success.
Authors: Crossin, Glenn, Phillips, Richard A., Trathan, Phil N., Fox, Derren S., Dawson, Alistair, Wynne-Edwards, Katherine E., Williams, Tony D.