Denning Phenology, Den Substrate, and Reproductive Success of Female Polar Bears (Ursus maritimus) in the southern Beaufort Sea 1986-2013 and the Chukchi Sea 1987-1994

These data represent estimates of den entrance and exit dates for female polar bears in the southern Beaufort and Chukchi Seas based on temperature sensor data obtained from satellite collars. An algorithm described in Olson et al. (2016) was used to determine whether the female entered a den and further analyses using temperature data as described in Olson et al. (2017) were used to assess den entry and emergence dates. The algorithm used identified periods in which temperature remained consistently above a temperature threshold. As such, users of these data should be aware that bear behavior can affect den entrance and exit date. If a bear moves in and out of a den frequently, the algorithm identifies that bear as not denning. Den substrate was determined by examining satellite locations from collars during the identified denning period and classify dens as occurring on landfast ice, sea ice, or land. This data set also includes direct observations of females post-den emergence including whether or not she was accompanied by cubs as an indicator of reproductive success.

本数据集基于卫星项圈（satellite collars）采集的温度传感器数据，对波弗特海南部与楚科奇海海域雌性北极熊的巢穴进出日期进行估算。本研究采用Olson等（2016）所述的算法，判定雌性北极熊是否进入巢穴；并通过Olson等（2017）所述的温度数据分析方法，进一步评估巢穴的进入与出穴日期。所采用的算法可识别出温度持续高于阈值的时段。据此，数据集使用者需注意：北极熊的行为会对巢穴进出日期的估算结果产生影响——若北极熊频繁往返于巢穴内外，则算法会判定该个体未开展筑穴活动。研究人员通过识别筑穴时段内项圈的卫星定位数据，判定巢穴基质类型，将巢穴划分为固定冰（landfast ice）、海冰（sea ice）或陆地三类。本数据集还包含雌性北极熊出穴后的直接观测数据，其中以是否伴随幼崽作为繁殖成功与否的判定指标。