Is bigger better? The relationship between size and reproduction in female Asian elephants
Is bigger better? The relationship between size and reproduction in female Asian elephants
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DOI：
10.1111/jeb.13143
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发表时间：
2017-10-01
影响因子：
2.1
通讯作者：
Lummaa, V.
中科院分区：
文献类型：
--
作者：
Crawley, J. A. H.;Mumby, H. S.;Lummaa, V.
资源的有限性预计将在动物的生长、繁殖和自我维持之间进行权衡。然而，尽管一些研究表明，早期繁殖抑制生长，但在其他情况下，繁殖与大小呈正相关。我们使用缅甸大量半圈养大象的详细记录来评估雌性亚洲象的大小（身高和体重），繁殖和生存之间的关系，这种物种的特点是缓慢，昂贵的生活史。虽然在生长期内雌性身高增长与种群中的生殖开始重叠很小，但首次生殖的年龄变化很大，在种群水平上只有81%的最终体重达到生殖高峰年龄（19岁）。那些早期开始繁殖的雌性在生命后期往往更高更轻，尽管这些趋势并不显著。我们发现，较高的女性更有可能在给定的年龄繁殖，但这种影响随着年龄的增长而减弱，这表明可能存在一个尺寸阈值，这对年轻女性尤其重要。由于大小与女性的生存在生殖年龄，随着年龄的增长，身高对生殖的影响递减不太可能是由于偏大的女性的生存。我们的结论是，虽然繁殖可能并不总是对生长产生重大影响，但身高可能是年轻雌性亚洲象繁殖的限制因素，考虑到它们的出生率很低，繁殖高峰期是年轻的-在这个种群中为19岁，这可能具有重要意义。
The limited availability of resources is predicted to impose trade-offs between growth, reproduction and self-maintenance in animals. However, although some studies have shown that early reproduction suppresses growth, reproduction positively correlates with size in others. We use detailed records from a large population of semi-captive elephants in Myanmar to assess the relationships between size (height and weight), reproduction and survival in female Asian elephants, a species characterized by slow, costly life history. Although female height gain during the growth period overlapped little with reproductive onset in the population, there was large variation in age at first reproduction and only 81% of final weight had been reached by peak age of reproduction at the population level (19years). Those females beginning reproduction early tended to be taller and lighter later in life, although these trends were not significant. We found that taller females were more likely to have reproduced by a given age, but such effects diminished with age, suggesting there may be a size threshold to reproduction which is especially important in young females. Because size was not linked with female survival during reproductive ages, the diminishing effect of height on reproduction with age is unlikely to be due to biased survival of larger females. We conclude that although reproduction may not always impose significant costs on growth, height may be a limiting factor to reproduction in young female Asian elephants, which could have important implications considering their birth rates are low and peak reproduction is young - 19years in this population.