Institut Pluridisciplinaire Hubert Curien (IPHC), Département Ecologie, Physiologie et Ethologie (DEPE), UMR 7178 CNRS-UdS, 23 rue Becquerel, 67087 Strasbourg, France.
J Exp Biol. 2010 Jan 1;213(1):33-9. doi: 10.1242/jeb.035378.
Foraging strategies play a key role in breeding effort. Little is known, however, about their connection with hormonal and nutritional states, especially when breeding constraints vary. Here, we experimentally increased foraging costs and thus breeding constraints by handicapping Adélie penguins (Pygoscelis adeliae) with dummy devices representing 3-4% of the penguins' cross-sectional area. We examined food-related stress (via plasma corticosterone concentration) and nutritional state (via metabolite levels). Concurrently, we investigated the use of ecological niches via the isotopic signature of red blood cells indicating the trophic position (delta(15)N) and the spatial distribution (delta(13)C) of penguins. Handicapped birds performed approximately 70% longer foraging trips and lost approximately 60% more body mass than controls and their partners. However, corticosterone levels and the nutritional state were unchanged. The isotopic signature revealed that males and females differed in their foraging behaviour: upper trophic levels contributed more in the males' diet, who foraged in more pelagic areas. Handicapped and partner birds adopted the same strategy at sea: a shift towards higher delta(13)C values suggested that they foraged in more coastal areas than controls. This change in foraging decisions may optimize feeding time by decreasing travelling time. This may partly compensate for the presumed lower foraging efficiency of handicapped birds and for the energetic debt of their partners who had to fast approximately 70% longer on the nest. We propose that this flexible use of ecological niches may allow birds facing increased breeding constraints to avoid chronic stress and to minimize the impact on their body condition.
觅食策略在繁殖努力中起着关键作用。然而，人们对它们与激素和营养状态的联系知之甚少，尤其是当繁殖限制不同时。在这里，我们通过用代表企鹅横截面积 3-4%的假设备来削弱阿德利企鹅（Pygoscelis adeliae），从而实验性地增加了觅食成本和繁殖限制。我们检查了与食物相关的应激（通过血浆皮质酮浓度）和营养状态（通过代谢物水平）。同时，我们通过红细胞的稳定同位素特征（表示营养级（δ15N）和企鹅的空间分布（δ13C））来研究生态位的利用。与对照组和其伴侣相比，残疾鸟进行了大约 70%更长的觅食旅行，并损失了大约 60%更多的体重。然而，皮质酮水平和营养状态没有变化。同位素特征表明，雄性和雌性在觅食行为上存在差异：雄性的饮食中更多地来自较高的营养级，它们在更多的远洋地区觅食。残疾鸟和伴侣鸟在海上采取了相同的策略：向更高的δ13C 值的转变表明它们在比对照组更多的沿海地区觅食。这种觅食决策的改变可以通过减少旅行时间来优化觅食时间。这可能部分补偿了残疾鸟的觅食效率降低以及它们的伴侣的能量债务，因为它们在巢上的禁食时间延长了大约 70%。我们提出，这种对生态位的灵活利用可以使面临繁殖限制增加的鸟类避免慢性应激，并将对其身体状况的影响降到最低。
