Blubber testosterone: A potential marker of male reproductive status in short‐beaked common dolphins

Abstract

A novel molecular technique was used to measure blubber testosterone (BT) in 114 male short‐beaked common dolphins, Delphinus delphis, collected from incidental fishery bycatch and strandings. When these concentrations were compared across maturity states, the mean (± SEM) BT levels of mature D. delphis (14.3 ± 3.0 ng/g) were significantly higher than those of pubertal (2.5 ± 0.5 ng/g, P= 0.006) and immature animals (2.2 ± 0.3 ng/g, P < 0.0001). BT concentrations in mature males were significantly higher in summer months (53.9 ± 2.0 ng/g) than during the rest of the year (7.9 ± 0.69 ng/g, P < 0.0001), indicating reproductive seasonality. An analysis of BT in different anatomical locations showed that hormone concentrations were not homogenous throughout the body; the levels in the dorsal fin were significantly lower than in most other areas (F= 5.39, P= 0.043). Conversely, we found no significant differences in BT concentration with respect to subepidermal depth (F= 2.09, P= 0.146). Finally, testosterone levels in biopsies from 138 free‐swimming male D. delphis, of unknown maturity state, sampled off California were found to be of concentrations similar to those from the fishery bycatch and stranding samples and revealed an analogous trend with respect to ordinal date.

Low reproductive success rates of common bottlenose dolphins Tursiops truncatus in the northern Gulf of Mexico following the Deepwater Horizon disaster (2010-2015)

“…The analysis was conducted within a Bayesian frame work to allow for better propagation of the measured uncertainty into the subsequent analyses. All blubber progesterone measurements were log transformed prior to analysis to minimize the heteroscedasticity that is common in hormone measurements (Kellar et al 2009(Kellar et al , 2015. The output generated estimates of the parameters for the best logistic regression fit and the 95% Bayesian credibility envelope around the re sulting function.…”

Review of cetacean biopsy techniques: Factors contributing to successful sample collection and physiological and behavioral impacts

“…Furthermore, as new assays become available, archived and future biopsy samples will be able to provide additional information on the health of individuals and the status of populations. For example, recent studies suggest that biopsies can provide information on stress levels through skin protein analyses (Southern et al 2002), pregnancy status through blubber progesterone analysis (Mansour et al 2002, Kellar et al 2006, male reproductive status through blubber testosterone analysis (Kellar et al 2009), and individual age through the analysis of blubber fatty acids (Herman et al , 2009.…”

Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?

“…This kit has been validated in short-beaked common dolphins (Delphinus delphis) for testing blubber testosterone concentrations [28]. Serum testosterone concentrations were assayed according to the manufacturer's specifications.…”