American marten (Martes americana) in Interior Alaska are at the northwestern limit of their North American range. To investigate factors that may be associated with reproduction we determined the cementum age and the presence or absence of blastocysts in 118 female martens for 3 years (2012, 2014, and 2016) in two regions. For each marten we collected fur samples and measured steroid hormone concentrations (cortisol, testosterone, and progesterone) and stable isotopes (δ15N and δ13C values, a proxy for diet). These parameters reflect the diet and endocrine activity between June and October when fur is grown. We also collected two claws from a subset of 39 female marten from one region in 2012 and 2014. Progesterone concentrations were measured in one whole claw and from a second claw divided into proximal (recent growth) and distal sections. Differences in the probability of blastocysts being present were associated with geographic region and sample year suggesting that reproduction in female marten varies on a fine scale. We found the that presence of blastocysts was positively associated with marten age and δ15N values in fur but negatively associated with fur cortisol concentrations. These findings suggest that the likelihood a female marten will reproduce in a given year is influenced, in part, by the proportion of protein in their diet and stressors encountered during late summer and fall, months before active gestation begins.

中文翻译：

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美洲貂 (Martes americana) 的年龄、饮食和压力相关激素与繁殖之间的关系

阿拉斯加内陆的美洲貂（Martes americana）位于其北美分布范围的西北部。为了调查可能与繁殖相关的因素，我们确定了两个地区 3 年（2012 年、2014 年和 2016 年）118 只雌性貂的牙骨质年龄和胚泡的存在与否。对于每只貂，我们收集了毛皮样本并测量了类固醇激素浓度（皮质醇、睾酮和孕酮）和稳定同位素（δ15N 和 δ13C 值，代表饮食）。这些参数反映了 6 月至 10 月生长毛皮时的饮食和内分泌活动。我们还在 2012 年和 2014 年从一个地区的 39 只雌性貂的子集中收集了两个爪子。黄体酮浓度在一个完整的爪子中测量，第二个爪子分为近端（最近生长）和远端部分。存在囊胚概率的差异与地理区域和样本年份有关，这表明雌性貂的繁殖在细微的范围内变化。我们发现囊胚的存在与貂年龄和毛皮中的 δ15N 值呈正相关，但与毛皮皮质醇浓度呈负相关。这些发现表明，雌性貂在给定年份繁殖的可能性部分受到其饮食中蛋白质的比例以及夏末和秋季（即活跃妊娠开始前几个月）遇到的压力源的影响。我们发现囊胚的存在与貂年龄和毛皮中的 δ15N 值呈正相关，但与毛皮皮质醇浓度呈负相关。这些发现表明，雌性貂在给定年份繁殖的可能性部分受到其饮食中蛋白质的比例以及夏末和秋季（即活跃妊娠开始前几个月）遇到的压力源的影响。我们发现囊胚的存在与貂年龄和毛皮中的 δ15N 值呈正相关，但与毛皮皮质醇浓度呈负相关。这些发现表明，雌性貂在给定年份繁殖的可能性部分受到其饮食中蛋白质的比例以及夏末和秋季（即活跃妊娠开始前几个月）遇到的压力源的影响。