Lowe Carley L, Hunt Kathleen E, Rogers Matthew C, Neilson Janet L, Robbins Jooke, Gabriele Christine M, Teerlink Suzie S, Seton Rosemary, Buck C Loren
Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA.
Department of Biology, George Mason University and Smithsonian-Mason School of Conservation, Front Royal, VA 22630, USA.
Conserv Physiol. 2021 Jul 28;9(1):coab059. doi: 10.1093/conphys/coab059. eCollection 2021.
Understanding calving rates of wild whale populations is critically important for management and conservation. Reproduction of humpback whales () is difficult to monitor and, even with long-term sighting studies, basic physiological information such as pregnancy rates and calving intervals remain poorly understood in many populations. We hypothesized that pregnant whales have sustained elevations in baleen progesterone that temporally correlate with gestation. To test this hypothesis, baleen progesterone profiles from two adult female North Pacific humpbacks, both with extensive sighting records and documented pregnancies, were compared to those of a nulliparous female (adult female never seen with a calf) and a juvenile male. Baleen specimens recovered during necropsy were subsampled every 2 cm from the base to the tip of the plate, with each interval representing 30-45 days of growth. Homogenized baleen powder was assayed for progesterone using enzyme immunoassays. The date of growth of each sampling location on the baleen plate was estimated based on stable isotope analysis of annual δN cycles. Progesterone profiles from both pregnant whales showed sustained high progesterone content (>350 ng/g) in areas corresponding to known pregnancies, inferred from calf sightings and post-mortem data. The younger female, estimated to be 13 years old, had higher progesterone during pregnancy than the 44.5 year old, but levels during non-pregnancy were similar. The nulliparous female and the male had low progesterone throughout their baleen plates. Baleen hormone analysis can determine how progesterone concentrations change throughout gestation and has potential for estimating age at first reproduction, pregnancy intervals, failed pregnancies and early calf mortality. Understanding rates of calving and current and historic reproductive patterns in humpbacks is vital to continuing conservation measures in this species.
了解野生鲸鱼种群的产犊率对于管理和保护至关重要。座头鲸的繁殖情况难以监测，即使通过长期的目击研究，许多种群中诸如怀孕率和产犊间隔等基本生理信息仍知之甚少。我们假设怀孕的鲸鱼其须鲸中孕酮水平持续升高，且在时间上与妊娠期相关。为了验证这一假设，将两只成年雌性北太平洋座头鲸（均有广泛的目击记录且有记录在案的怀孕情况）的须鲸孕酮谱与一只未生育的雌性（从未见过有幼崽的成年雌性）和一只幼年雄性的须鲸孕酮谱进行了比较。在尸检过程中回收的须鲸标本从板的基部到尖端每2厘米进行一次取样，每个间隔代表30 - 45天的生长时间。使用酶免疫分析法对匀浆后的须鲸粉末进行孕酮检测。根据年度δN循环的稳定同位素分析来估计须鲸板上每个取样位置的生长日期。两只怀孕鲸鱼的孕酮谱在与已知怀孕相对应的区域均显示出持续的高孕酮含量（>350 ng/g），这是根据幼崽目击情况和尸检数据推断出来的。估计年龄为13岁的较年轻雌性在怀孕期间的孕酮水平高于44.5岁的雌性，但非怀孕期间的水平相似。未生育的雌性和雄性的整个须鲸板中的孕酮水平都很低。须鲸激素分析可以确定孕酮浓度在整个妊娠期如何变化，并且有潜力用于估计首次繁殖的年龄、怀孕间隔、怀孕失败情况和幼崽早期死亡率。了解座头鲸的产犊率以及当前和历史繁殖模式对于该物种持续的保护措施至关重要。
