Chronological monitoring of nutritional and hormonal status of elephant seals through whisker analysis

• Main Author: Lübcker, Nico
• Other Authors: De Bruyn, P.J. Nico, Millar, Robert Peter
• Format: Thesis
• Language: English
• Published: University of Pretoria 2020
• Subjects: UCTD; Zoology; Elephant Seals; Marion Island; Mirounga leonina; Southern Elephant Seals
• Online Access: http://hdl.handle.net/2263/74409

Environmental perturbations impose selection pressures on organisms. The adaptive physiological mechanisms employed by species to survive in their changing environments are fundamental for their persistence. It is postulated that intraspecific variation observed in the reproductive pattern of adult female southern elephant seals (SES, Mirounga leonina) at Marion Island, as well as in other species, is caused by food availability and individual differences in their foraging habits and nutritional status. However, it remains challenging to obtain dietary and physiological data from cryptic organisms at a longitudinal resolution. Sequentially subsampled biologically inert tissues, such as hair, nails, whale baleen, and whiskers (vibrissae) can provide a retrospective biochemical record of the organism. The goal of this dissertation was to develop a biomarker to assess the nutritional and physiological status of free-ranging SES, using chronologically analyzed whiskers sampled from either adult females or their offspring. We combined bulk tissue (whole whisker segment) and amino acid nitrogen (δ15N) isotope values measured chronologically along the length of their whiskers to demonstrate that apart from ecological factors, physiological factors such as fasting, also affects the measured bulk tissue and constituent amino acid-specific δ15N values. In addition, we tested whether the stable isotope values measured in the intrauterine grown tissues of offspring can be utilized as proxies for their mothers’ isotope values during gestation. In contrast to previous studies, we conclusively demonstrated that paired, temporally matched, mother-offspring bulk tissue δ15N and carbon isotope (δ13C) values of SES are not in isotopic equilibrium or linearly correlated during gestation. Also, the relationship between mother-offspring δ15N and δ13C values (Δ) changed as gestation progressed. Fetal development relies primarily on remobilized endogenous maternal proteinaceous sources. We caution against the utilization of offspring ...