Department of Zoology and Genetics, Iowa State University, Ames, Iowa 50011.
Integr Comp Biol. 2002 Feb;42(1):76-83. doi: 10.1093/icb/42.1.76.
Animals must make "decisions" (e.g., when or whether to breed, the effort to put into a breeding episode) by integrating physiological, environmental and social inputs. This integration can be studied only in a field context. In Adélie penguins (Pygoscelis adeliae) reproduction is constrained by foraging ecology, mode of transport, and the extreme latitude at which they live. The decision whether to breed in a given year is influenced by body conditions. Adélie penguins must fast for several weeks during the early reproductive stages and use stored fat for metabolic energy. Females that return to the colony, but do not breed, are 10-12% lighter than females that do breed. Birds that are relatively low in body mass tend to have lower reproductive success than heavier birds, and an individual's reproductive success is positively correlated with the body fat stores it had on arrival. After eggs are laid, parents alternate in attending the nest. Nest failure occurs if one parent does not make a timely return and its fasting partner must eventually leave. During normal-length fasts plasma corticosterone and glucose levels do not change. Blood β-hydroxybutyrate levels gradually increase during the fast while uric acid levels remain low, but in birds with the longest fasts (>∼50 days), ketone levels may fall and uric acid levels increase, indicative of a switch from using fat to using body proteins for metabolism. In incubating males, hematocrit and hemoglobin concentrations also increase, suggesting dehydration can accompany energy stress during the breeding fast.
动物必须通过整合生理、环境和社会输入来做出“决策”（例如，是否繁殖，繁殖过程中的努力程度）。这种整合只能在实地背景下进行研究。在阿德利企鹅（Pygoscelis adeliae）中，繁殖受到觅食生态学、运输方式和生活的极端纬度的限制。在给定的年份是否繁殖的决定受到身体状况的影响。阿德利企鹅在繁殖的早期阶段必须禁食数周，并利用储存的脂肪作为代谢能量。返回繁殖地但不繁殖的雌性比繁殖的雌性轻 10-12%。体重相对较低的鸟类往往比体重较重的鸟类繁殖成功率低，个体的繁殖成功率与其到达时的体脂储存量呈正相关。产卵后，亲代会轮流孵卵。如果一方父母不能及时返回，巢就会失败，其禁食伴侣最终必须离开。在正常的禁食期间，血浆皮质醇和葡萄糖水平不会改变。在禁食期间，血液 β-羟基丁酸水平逐渐升高，尿酸水平保持较低，但在禁食时间最长的鸟类（>∼50 天）中，酮体水平可能下降，尿酸水平升高，表明代谢从利用脂肪转变为利用身体蛋白质。在孵卵的雄性中，红细胞压积和血红蛋白浓度也会升高，表明在繁殖期间，脱水可能伴随着能量压力。
