Catry Paulo, Phillips Richard A, Phalan Ben, Croxall John P
British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
Proc Biol Sci. 2006 Jul 7;273(1594):1625-30. doi: 10.1098/rspb.2006.3482.
Studies attempting to document reproductive or other pre-lethal senescence effects in wild birds typically face an array of problems, including flaws in statistical analyses, non-adaptive philopatry to deteriorating environments, confounding effects arising from cohort heterogeneity and differential death rates of phenotypes and the frequent pairing of old birds to younger mates. Furthermore, recent studies suggest that birds could maintain a high level of physical fitness until old age, before being struck by a catastrophic illness leading quickly to their demise. The presence of terminally ill individuals in most datasets (and their greater incidence in older age categories) may therefore provide a false impression of progressive senescence in cross-sectional analyses. This study was designed explicitly to avoid all the known pitfalls linked to the demonstration of progressive senescence in wild populations, and involved one of the very longest-lived bird species. We show that, during incubation, old (aged 35 years and over) male grey-headed albatrosses Thalassarche chrysostoma make longer foraging trips, and have lower daily mass gains, than experienced mid-aged individuals (aged up to 28 years). This is, to our knowledge, the first report documenting reduced foraging performance with old age. Hatching and breeding success of pairs composed of two old individuals were reduced in comparison to mid-aged pairs. Overall results were very similar when analyses were repeated using only individuals known to have survived 1 or 2 years beyond field measurements (hence probably not suffering from the effects of an advanced terminal illness). We conclude that extremely long-lived individuals usually experience some degree of general physical deterioration, leading to reduced foraging and breeding performance, long before their final demise.
试图记录野生鸟类繁殖或其他致死前衰老效应的研究通常面临一系列问题，包括统计分析中的缺陷、对恶化环境的非适应性留居、群体异质性以及表型死亡率差异所产生的混杂效应，还有老鸟与年轻配偶频繁配对的情况。此外，最近的研究表明，鸟类在老年之前能够保持较高的体能水平，直到遭遇一场灾难性疾病并迅速导致死亡。因此，大多数数据集中存在绝症个体（且在老年类别中更为常见）可能会在横断面分析中给人一种渐进性衰老的错误印象。本研究旨在明确避免与证明野生种群渐进性衰老相关的所有已知陷阱，并且涉及一种寿命极长的鸟类。我们发现，在孵化期间，35岁及以上的老年雄性灰头信天翁（Thalassarche chrysostoma）比经验丰富的中年个体（年龄最大28岁）觅食行程更长，每日体重增加更低。据我们所知，这是第一份记录随着年龄增长觅食能力下降的报告。与中年配对相比，由两只老年个体组成的配对的孵化和繁殖成功率降低。当仅使用已知在野外测量后存活1年或2年（因此可能未受晚期绝症影响）的个体重复分析时，总体结果非常相似。我们得出结论，寿命极长的个体通常在最终死亡之前很久就会经历某种程度的身体普遍衰退，导致觅食和繁殖能力下降。
