Busted! First Detection of Steroid Hormones in Pacific Walrus Bones

The Pacific walrus (Odobenus rosmarus divergens) is a candidate for the Endangered Species List, because climate warming could affect habitat use and food web structure. With the current change of the Arctic ecosystem, it is unclear how walruses will respond to these possible stressors. In this novel study, steroid hormones (i.e., progesterone, testosterone, estradiol, estriol, and cortisol) were extracted from archeological (927-3,585 years old), historical (34-81 years old), and modern (year 2014 samples) bones to determine if hormones could be detected in bones of various ages. Lipids were removed and subsequently steroid hormones, from powdered bone using a methanol extraction procedure. Hormone levels were analyzed and validated by liquid chromatography triple quadrupole mass spectrometry (LC-QQQ MS). Progesterone, testosterone, cortisol, and estriol were detected, while estradiol concentrations were below the detection limit (<1 ng/g) in all samples. We were able to detect cortisol in archaeological (n=1 of 7, 3.71 ng/g), historical (n=3 of 52 mean= 4.07 ng/g), and modern (n=1 of 10, 6.56 ng/g) bone samples. Progesterone was detected in archaeological (n=4 of 7, mean= 1.47 ng/g), historical (n=51 of 52, mean=14.76 ng/g), and modern (n=8 of 10, mean=10.08) bone samples. Testosterone was detected in archaeological (n=3 of 7, mean= 0.24 ng/g), historical (n=26 of 52, mean=0.98 ng/g), and modern (n=6 of 10, mean=1.03 ng/g). Estriol was only detected in archaeological (n=7 of 7, mean= 79.04 ng/g) bone samples. These results validate our method of steroid hormone extraction and are the first to address environmental interactions and physiological responses in historic and pre-historic walrus populations.