Biological matrices for sampling free‐ranging cetaceans and the implications of their use for reproductive endocrine monitoring

Abstract

Abstract Monitoring reproductive rates in wild cetaceans is a crucial step towards adequate management of their populations. Their reproductive hormone profiles can be of importance, especially when combined with behavioural or life history monitoring. Sampling biological matrices of wild, free‐ranging cetaceans can be a difficult task. The purposes of this review are: to describe briefly the different methods available for monitoring the reproductive endocrine parameters of wild and captive cetaceans, and to evaluate the feasibility of using various matrices – blood, urine, faeces, saliva, bubbler, muscle, ocular secretions, blow (respiratory vapour), milk, baleen, and earplug materials – to measure sex hormones in free‐ranging cetaceans. We performed a retrospective analysis of the measurement and sample collection methods and the most commonly used matrices for constructing reproductive hormone profiles. The PubMed and Google Scholar data bases were used, and scientific articles and book chapters published from 1980 to the present were considered. In the past, the most commonly used matrix for measuring hormones of free‐ranging cetaceans was blood. This has been changing since studying live whales became more common: researchers have dispensed with using blood samples from dead animals. Matrices such as blow, which can be obtained non‐invasively, and other matrices that can be obtained with minimal invasion, such as blubber, appear to be feasible options for monitoring the hormones of live, free‐ranging cetaceans.