Luminous intensity and dive depth profile data of emperor penguins from Pointe Géologie, Adélie Land, Antarctica, from expedition DDU 2005

The foraging ability of visual hunters depends critically on light conditions. Emperor penguins Aptenodytes forsteri are reported to be visual hunters, but breed and forage at high latitudes and are thus exposed to extreme changes in light conditions in the course of the year. We examined how light influenced the foraging ability of breeding emperor penguins using loggers in winter (n = 5) and spring (n = 4) 2005 (see doi:10.1594/PANGAEA.633713) at Pointe Géologie (66° 40' S, 140° 01' E), Antarctica, as well as by using models of light availability over the year and as a function of depth. The model showed that daylight was continuous between days of the year 350 and 363 and that the sun did not rise between days of the year 166 and 180. Logger-measured light intensity decreased with water depth, and depth-specific values were higher at greater sun elevation angles. Depth-time use (given by the maximum depth reached multiplied by the number of hours at which this depth could be achieved over 24 h) of spring-foraging penguins was 8394.5 m x h, which was more than twice that of winter-foraging birds at 3845.4 m x h, showing the severe constraints imposed by winter conditions. Average catch-per-unit effort was related to mean maximum diving depth and was highest around mid-day in winter and highest during dawn and dusk in spring. This reflects availability of prey to foraging emperor penguins.

视觉猎手的觅食能力极大程度依赖光照条件。帝企鹅（Aptenodytes forsteri）被认定为视觉猎手，但其繁殖与觅食活动均在高纬度区域开展，因此全年会经历光照条件的极端变化。2005年，我们于南极乔治地角（66°40′S，140°01′E）开展研究，通过部署记录仪（loggers）获取数据（冬季样本量n=5，春季样本量n=4，详细信息见doi:10.1594/PANGAEA.633713），同时结合全年光照可用性模型及深度关联光照模型，探究了光照对繁殖期帝企鹅觅食能力的影响。模型结果显示，每年第350天至第363天为连续白昼（极昼）时段，而每年第166天至第180天期间太阳未升起。记录仪测得的光照强度随水深增加而降低，且太阳高度角越大，对应深度的光照数值越高。春季觅食企鹅的深度-时间利用量（以单日最大可达深度乘以该深度在24小时内可实现的小时数计算）为8394.5米·小时，是冬季觅食企鹅（3845.4米·小时）的两倍以上，这表明冬季环境对其觅食活动存在极强的限制作用。单位捕捞努力量渔获量（catch-per-unit effort）的平均值与平均最大潜水深度相关：冬季的峰值出现在正午前后，而春季则在黎明与黄昏时段达到最高，这一结果反映了帝企鹅觅食时猎物的可获得性特征。