Determining Pregnancy From Blubber in Three Species of Delphinids

Abstract

We quantified progesterone in 110 blubber samples from dolphins of known reproductive status in order to test the accuracy of a method to determine pregnancy status in wild cetaceans. The samples were collected from fishery‐bycaught delphinids of three species (Delphinus delphis, Lissodelphis borealis, and Lagenorhynchus obliquidens). We ascertained that blubber progesterone concentrations could clearly distinguish pregnant D. delphis (range 132–415 ng/g, mean 261 ng/g) from non‐pregnant mature and immature ones (range 0.92–48.2 ng/g, mean 15.2 ng/g). We found similar dramatic differences in L. borealis and L. obliquidens. These results were insensitive to various blubber sampling depths and anatomical sampling locations on the body, suggesting relative homogeneity of progesterone levels throughout the blubber. However, no trend was found in blubber progesterone concentration with fetal length, indicating that although blubber progesterone appears to distinguish pregnancy status, it is unlikely to differentiate pregnancy stage. Based on the findings presented here we suggest that this method, when coupled with projectile biopsy procedures, can be used to assess the pregnancy status of free‐ranging cetaceans and thus provide a new tool to determine pregnancy rates of wild populations.

Variation of bowhead whale progesterone concentrations across demographic groups and sample matrices

“…The blubber hormone extractions followed the methods delineated by Kellar et al (2006) with several modifications to simply the procedure and increase consistency. Approximately 0.5 g of blubber was homogenized 7 to 9 times at a speed of 5 m s −1 for 45 s intervals depending on sample consistency.…”

“…Other sample materials from which these hormones have been extracted and measured include milk (West et al 2000), muscle (Yoshioka et al 1994), cetacean exhalant or blow (Hogg et al 2005), bone, and ocular secretions (Atkinson et al 1999). Only a scant few studies have measured reproductive hormones from adipose tissue of any kind, let alone blubber (Hillbrand & Elsaesser 1983, Ha mu di ku wanda et al 1996, Mansour et al 2002, Kellar et al 2006, though one of these does include data from minke whales Balaenoptera acutorostrata, a species of baleen whale (Mansour et al 2002). Consequently, the relationships between hormone levels and their specific effects on mammalian biology have not been delineated for blubber tissue, and because this tissue is very different in chemistry, structure, and dynamics from these more commonly used matrices, we would not necessarily expect to find a simple relationship between blubber hormone concentrations and concentrations obtained from more routinely measured matrices.…”

“…They are the biological samples most frequently collected from freeranging cetaceans and are often obtained in numbers suitable for estimates of population-level demographic parameters. Recently, a number of studies have begun measuring steroid hormones from blubber tissue in efforts to glean additional biological information from these samples (Kellar et al 2006, 2009, Amaral 2010, Pérez et al 2011. In particular, progesterone, the hormone responsible for sustaining gestation, found in blubber samples has been empirically accurate at differentiating/diagnosing pregnancy state (Mansour et al 2002, Kellar et al 2006, Pérez et al 2011.…”

Multi-year longitudinal profiles of cortisol and corticosterone recovered from baleen of North Atlantic right whales (Eubalaena glacialis)

“…However, some alternative sample types can be collected from whales, including feces, blubber biopsy dart samples, and respiratory vapor (e.g., Hogg et al, 2005Hogg et al, , 2009Hunt et al, 2006Hunt et al, , 2013Hunt et al, , 2014aKellar et al, 2006;Rolland et al, 2005;Vu et al, 2015). For example, fecal GCs of North Atlantic right whales (Eubalaena glacialis, NARW) show significant increases corresponding with energetically-demanding states such as pregnancy and lactation, as well as with anthropogenic stressors of chronic ocean noise and entanglement Hunt et al, 2006;Rolland et al 2005Rolland et al , 2012.…”

Development of a Nonlethal and Minimally Invasive Protocol to Study Elasmobranch Reproduction

“…For example, steroid hormones have been extracted from milk and/or muscle tissues from cows (Noppe et al 2008), sheep, and chickens (Sawaya et al 1998); the urine and feces of free-ranging wildlife (Lasley and Kirkpatrick 1991;Holt and Pickard 1999); blubber from marine mammals (Mansour et al 2002;Kellar et al 2006); and the skeletal muscle tissue of a chimaera, the Spotted Ratfish Hydrolagus colliei (Barnett et al 2009), for various reproductive analyses. Despite the successful extraction of steroid hormones from body depots other than plasma, this approach has never been taken with an elasmobranch.…”