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Sex ratios in blue whales from conception onward: effects of space, time, and body size
Marine Mammal Science ( IF 2.3 ) Pub Date : 2020-09-19 , DOI: 10.1111/mms.12741
Trevor A. Branch 1 , Cole C. Monnahan 1
Affiliation  

Deviations from equal sex ratios in mammals can reveal insights into sex‐specific growth, survival, movements, and behavior. We assessed blue whale (Balaenoptera musculus) sex ratios based on 21,542 fetal and 311,901 whaling records, finding that males were slightly but significantly more common than females (51.3% fetal, 52.1% postnatal). Antarctic catches shifted from 52.4% male before 1951 to 48.0% male thereafter, even though larger females were preferentially targeted by whalers and should have declined. The southernmost land stations caught more males than those in southern Africa, and at land stations, sex ratios shifted subtly over the course of a year. Pelagic catches demonstrated spatial structure in sex ratios, including more males being caught in the Ross Sea. In utero, the smallest females were often misidentified as males, and there was some evidence for higher prenatal male mortality. Once born, medium‐sized blue whales within each region were more often male, while the longest were nearly all female; explained entirely by females growing faster and reaching longer sizes. Overall, though, sex ratios are remarkably close to equality across time, space, and length; with any deviations best explained by faster female growth and size‐selective whaling.

中文翻译:

从受孕开始的蓝鲸性别比例:空间,时间和体型的影响

哺乳动物性别平等比例的差异可以揭示对特定性别的生长,生存,运动和行为的见解。我们评估了蓝鲸(Balaenoptera musculus)的性别比是根据21,542胎和311,901捕鲸记录得出的,发现男性比女性稍常见,但明显多于女性(51.3%的胎儿,52.1%的出生后)。南极捕捞量从1951年之前的52.4%雄性转变为之后的48.0%雄性,尽管较大的雌性是捕鲸者的优先目标,而且本应下降。最南端的陆地电台捕获的男性比南部非洲更多,而在陆地电台中,性别比例在一年的时间里发生了微妙的变化。中上层鱼类的捕获显示出性别比例的空间结构,其中包括在罗斯海捕获的更多男性。在子宫内,最小的女性经常被误认为是男性,并且有一些证据表明产前男性死亡率较高。出生后,每个地区的中型蓝鲸多为雄性,最长的几乎是女性;完全由女性成长更快,体型更大的原因来解释。总体而言,性别比例在时间,空间和长度上都非常接近平等。最好的解释是雌性更快的成长和对尺寸的捕鲸。
更新日期:2020-09-19
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