Northern elephant seals migrate long distances from feeding grounds to raise pups during a brief period on breeding beaches. Since gestation sets a parturition date months in advance, timing of the arrival must be precise. We used satellite-tracked animals to examine this timing, establishing arrival and birth dates in 106 migrating females and estimating how far they traveled in the days just before birth. Females arrived a mean of 5.5 days prior to birth (range 1-11, sd=1.6), and females arriving later in the breeding season cut that pre-birth interval by 1.8 days relative to early arrivers. There was no correlation between female body condition, nor female age, and the pre-birth interval. The last 15 days prior to birth, animals traveled as far as 1465 km. Those furthest from the colony traveled > 100 km per day, three times faster than animals near the colony at the same time. Despite migrations covering several thousand kilometers while pregnant, female elephant seals were able to time their arrival within 6 days, swimming steadily at high speed if needed. This allows them to maintain a precise annual cycle for many years consecutively.

中文翻译：

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象海豹长时间进食迁徙后的出生时间

在繁殖海滩上的短暂时间内，北象海豹从觅食地迁移很长的距离来养幼崽。由于妊娠会提前几个月确定分娩日期，因此到达的时间必须准确。我们使用卫星跟踪的动物检查了这一时间，确定了106名移徙雌性的到来和出生日期，并估计了他们在出生前几天的旅行距离。雌性平均在出生前5.5天到达（范围1-11，标准差= 1.6），雌性在繁殖季节中到达的时间比早来者缩短了1.8天。女性的身体状况，女性的年龄与出生间隔之间没有相关性。出生前的最后15天，动物走了1465公里。距离殖民地最远的居民每天旅行> 100公里，同时比殖民地附近的动物快三倍。尽管在怀孕期间进行了数千公里的迁徙，雌海豹仍能在6天内安排其到达时间，并根据需要稳定地高速游泳。这使他们可以连续多年保持精确的年度周期。