Meeting Abstract
Baleen consists of filter-feeding sheets, or “plates”, of cornified tissue that grow continuously from the upper jaw of mysticete whales, gradually wearing off at the distal end. We have recently demonstrated that baleen contains steroid hormones that are likely deposited from circulation during the period of tissue growth. Given species-specific baleen growth rates and length of adult baleen, a single plate may represent a continuous endocrine record of the past decade or longer. To test whether baleen hormones reflect known reproductive state, we analyzed multiple subsamples of baleen from sixteen bowhead whales (Balaena mysticetus) collected during subsistence harvests in northern Alaska. The sixteen animals included both sexes and a mix of reproductive states and ages (mature and immature males; and mature nonpregnant, pregnant, and immature females). In baleen from the gumline (newest baleen), all pregnant bowheads had higher baleen progesterone than all other bowheads. Pregnant females also exhibited progesterone “profiles” in older baleen (e.g. baleen grown over the past year) that were consistent with estimated gestation length of bowhead whales. Furthermore, several of the nonpregnant mature females had very high progesterone in older baleen (grown more than a year prior), suggesting that baleen might provide an endocrine record of previous pregnancies. Though the technique is still under development, baleen may enable assessment of inter-calving intervals, reproductive trends, and adrenal activity over multi-year timeframes, information that is very difficult to acquire in large whales by other means.
