Maternal investment and factors affecting offspring size in polar bears (Ursus maritimus)
Maternal investment and factors affecting offspring size in polar bears (Ursus maritimus)
复制标题
DOI：
10.1017/s095283699800702x
复制
发表时间：
1998-07-01
影响因子：
2
通讯作者：
Stirling, I
中科院分区：
文献类型：
--
作者：
Derocher, AE;Stirling, I
我们研究了哈得逊湾西部活捕北极熊（Ursus maritimus）的数据，并与差异性母性投资和兼性性别比理论相关。春天，在巢穴出现后不久，我们发现一窝或两窝幼崽的质量或体长没有差异。在春季捕获的三胞胎中，雄性幼崽的质量和体长都大于雌性，这可能是由于兄弟姐妹争夺有限的母性资源。在秋季捕获的幼崽中，仅在雄性大于雌性的一窝幼崽中发现了体重和体长的性别差异。秋季捕获的一岁和两窝一岁雄性比雌性更重、更长。在春季和秋季的一窝雄性和一只雌性幼崽中，我们发现体重或体长没有差异。除春季单胎雌性幼崽和春季雌雄三胞胎外，幼崽和一岁体重与母体质量相关。春季有单胎的母亲更有可能生下雄性幼崽，但总的来说，几乎没有证据表明母亲的体重或年龄会影响后代的性别。产仔数、母体质量和母体年龄都会影响幼崽和一岁幼体的大小，但后代的性别不太重要。结果表明，除了春季的三胞胎外，雌性北极熊通常不会在不同性别的后代之间进行差异化的投资。
We examined data on live-captured polar bears (Ursus maritimus) from western Hudson Bay relative to differential maternal investment and facultative sex ratio theory. In spring, shortly after den emergence, we found no differences in mass or body length of cubs in litters of one or two. In triplet litters captured in spring, male cubs were larger than females in both mass and body length, possibly due to sibling competition for limited maternal resources. In cubs captured during autumn, sex-based differences in mass and body length were found only in litters of one with males larger than females. Yearling males captured in autumn were heavier and longer than females in litters of one and two. In twin litters of one male and one female cub in spring and autumn, we found no differences in mass or body length. Except singleton female cubs in spring and female and male triplets in spring, cub and yearling mass were correlated with maternal mass. Mothers with singletons in spring were more likely to have male cubs but, in general, there was little evidence to suggest that mass or age of mothers influenced offspring sex. Litter size, maternal mass, and maternal age all influenced cub and yearling size, but offspring sex was less important. Results suggest that female polar bears do not normally invest differentially between offspring of different sexes except in triplet litters in spring.