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

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.

Endocrine profiling of reproductive status and evidence of pseudopregnancy in the Pacific walrus (Odobenus rosmarus divergens)

“…Profiling hormone concentrations in the tissues of walruses demonstrates that endocrine analyses are potentially useful indicators in determining reproductive states of this species. While this has been done in multiple species with many types of matrices [2,3], no studies using ovarian tissue of marine mammals for endocrine analyses were found in published literature. The ovarian tissues used in this study are unique in that they are the source location in which progesterone and estrogens are produced, rather than the more commonly sampled matrices used in endocrinology studies of marine mammals such as blood, blubber, and feces [2,3].…”

“…While this has been done in multiple species with many types of matrices [2,3], no studies using ovarian tissue of marine mammals for endocrine analyses were found in published literature. The ovarian tissues used in this study are unique in that they are the source location in which progesterone and estrogens are produced, rather than the more commonly sampled matrices used in endocrinology studies of marine mammals such as blood, blubber, and feces [2,3]. This allowed the measurement of sex steroid hormones from the animal at the time of sampling and directly from the production site.…”

“…Reproductive hormone profiles can be used to detect pregnant and non-pregnant animals, and has been demonstrated in multiple marine mammal species [1][2][3]. For this reason, endocrinology has gained traction as a tool for determining pregnancy in animals in human care, as well as in wild populations.…”

Multiple steroid and thyroid hormones detected in baleen from eight whale species

“…Significant progress has been made at recovering and quantifying some of the hormones described above from alternative tissue types in cetaceans, particularly faecal samples, respiratory vapour (‘blow’), and biopsy dart samples of skin and blubber ( Rolland et al , 2005 ; Hunt et al , 2006 , 2014a ; Kellar et al , 2006 ; reviewed in Hunt et al , 2013 ; De Mello and de Oliveira, 2016 ) and most recently earwax plugs ( Trumble et al , 2013 ). For example, progestagens in faeces, blow and blubber are significantly elevated in pregnant females, while faecal glucocorticoids and mineralocorticoids have been shown to correlate with exposure to environmental stressors such as chronic ocean noise and fishing gear entanglement ( Rolland et al , 2005 ; Hunt et al , 2006 ; Hogg et al , 2009 ; Kellar et al , 2013 ; Burgess et al , 2017 ).…”

An Economical Custom-Built Drone for Assessing Whale Health

“…Sampling exhaled breath or 'blow' from wild whales may therefore provide a more representative assessment of the health status of individuals because samples can be randomly taken from the population. From a single sample of whale blow, scientists may be able to collect respiratory bacteria, lipids, proteins, DNA and hormones (Hogg et al, 2005(Hogg et al, , 2009Schroeder et al, 2009;Acevedo-Whitehouse et al, 2010;Hunt et al, 2013Hunt et al, , 2014Thompson et al, 2014;Burgess et al, 2016;De Mello and De Oliveira, 2016;Raverty et al, 2017). This information is important for whale conservation, as it can be collected over time to help monitor the recovery of whale populations postwhaling.…”