Measuring Reproductive and Stress Hormones in Humpback Whales - Sea Mammal Research Unit, Scotland.
In an on-going project in collaboration with researchers at the Sea Mammal Research Unit of the University of St. Andrews (Scotland), the levels of reproductive and stress hormones are measured in blubber biopsy samples and blow samples collected from humpback whales. Reproductive hormone levels, particularly progesterone, have been measured in cetacean blubber samples and blow samples as indicators of pregnancy in various cetacean species. Other studies have shown, that high progesterone levels are indicative of pregnancy. Therefore, we can collect information on pregnancy rates in our humpback whale population, as well as, calf survival rates, when females are seen the following season with or without a calf.
In the same matrices, the blubber and the blow, the stress hormone cortisol will also be measured. In their natural environment, animals experience a variety of environmental and anthropogenically influenced conditions, which can induce a physiological stress response. Stress responses can be short-term (acute) or long-term (chronic), and because of potentially harmful effects of chronic stress on various aspects of animal physiology, including immune function and reproductive output, there is a growing interest in measuring stress in wild animals. This study will attempt to understand how to measure stress in free-ranging whales, cortisol in blubber biopsy samples will be analysed as an indicator of chronic stress, while cortisol levels in the blow will be analysed as an indicator of acute stress.
Reproduction and body condition of humpback whales
Jo Kershaw, a first year PhD student at the University of St Andrews and member of the MICS team, is currently undertaking a collaborative project between the two research institutes to investigate novel ways of measuring the body condition of free-ranging whales. The body condition of individuals is a measure of their fat reserves, and is a good predictor of their resilience to potential environmental fluctuations and anthropogenic impacts, and also of their reproductive health and potential. Despite its importance, current methods of estimating the body condition of free ranging cetaceans are descriptive, subjective or inapplicable to most species. Jo will address this gap in our ability to measure cetacean body condition by investigating and validating novel, robust methods of estimating the condition of free ranging cetaceans using biomarkers in their blubber. Cetaceans are unique among mammal species in that their fat reserves can be sampled directly through biopsy sampling of their blubber layer. As such, cetacean blubber presents an excellent opportunity for minimally invasive sampling to gain insight into the condition of live animals. Therefore, this work aims to develop methods of estimating the body condition of cetaceans using both the types and quantities of fats and hormones in their blubber as biomarkers of overall condition.