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Bears forgo a lot of activities to conserve their energy in the winter when food is
在食物短缺的冬天 为保存能量 熊不再进行许多生命活动
scarce – even important bodily functions like eating, and peeing, and pooping.
甚至一些重要的机体功能 如进食 排泄都被摒弃
But they aren’t just saving energy for an extra-long nap –
但以此 熊不仅为超长休眠期保留能量
they also give birth during hibernation. Yeah, bears have their babies while they’re
在冬眠期 它们还会生崽 没错 冬天藏窝里
tucked away in their dens for the winter!
它们会干这事
This seems like it would be the harshest possible time of year
一年里 在这个时间段生崽 似乎再艰难不过
for cubs to be born, especially when they’re pretty much stuck inside.
尤其它们还困在窝里 几乎出不去
So how and why does that happen?
那么冬眠期的熊如何生崽 原因又是什么？
Hibernation is a state of inactivity that many warm-blooded animals,
冬眠是一种生理活动下降的状态 一年中许多恒温动物
like bears, enter for several months out of the year.
如熊的这种状态会持续数月
But contrary to popular belief, this physiological state isn’t just a
但与主流观点相悖的是 该生理状态并非
really long sleep when the temperatures drop.
降温时出现的极长休眠
Instead, it’s an extended period of torpor – a state of reduced activity that is
相反 该状态为延长的休眠期 即处于不利环境及
triggered in adverse environments and during periods of food scarcity.
食物短缺期引发的 生命活动降低的状态
During torpor, an animal’s metabolism, breathing,
在休眠期 动物的代谢减慢 呼吸变缓
and heart rate slow down and its body decreases temperature.
心率放慢 体温降低
Animals can go in and out of torpor daily or it can last for several days,
动物的休眠期可以是一天 也可以持续数天
weeks, or months, at which point it’s referred to as hibernation.
数周或数月 如为后者 即被称作冬眠状态
Some researchers have called bears super hibernators because their body
有研究者称熊为冬眠强者 因为与体型较小的冬眠动物
temperatures only drop a few degrees, in contrast with smaller hibernators like
如松鼠相比 它们的体温仅降低几度
squirrels, whose body temperatures drop to near freezing.
而松鼠的体温会降至近零度
Because they don’t have to unthaw themselves,
因为熊不需要预热
bears can react to any potential threats really quickly.
它们对任何潜在威胁的反应非常灵敏
And even if they look like they’re sleeping,
而且就算看上去在打盹
bears are still aware of their surroundings.
它们对周围环境的感知依旧敏锐
A paper published in 2011 reported that black bear heart rates increased as soon
据2011年发表过的一份文章报道 研究人员一靠近黑熊的窝
as researchers approached their dens,
它们的心率便立刻加快
indicating the bears could detect the potential danger outside.
这表明 熊可以侦测出外界的潜在危险
They also found that pregnant black bears’ heart rates increased as their
研究者还发现 雌性黑熊随着怀孕周期推进
pregnancy progressed, and the bears moved even less once the babies arrived,
心率也随之加快 而幼崽一出生 母熊甚至会减慢移动速度
to probably avoid accidentally crushing them.
这可能是为了避免和幼崽意外相撞
When the babies are first born, they only
初生幼崽仅需取暖
require warmth and a constant supply of milk.
以及不间断的哺乳
As long as the female has adequately prepared before hibernation,
只要母熊冬眠前准备充分
she can provide for both herself and the cubs.
便可以供养自己和幼崽
To do that, bears have to build up a massive fat store in order
为此 它们得有庞大的脂肪贮存
to survive several months of hibernation.
以熬过数月之久的冬眠期
Their bodies slowly metabolize those fat stores to use as a food and water source.
熊体内贮存的脂肪被机体缓慢代谢 以供给食物和水
Their bodies even turn waste products into proteins to keep their
甚至代谢废物也被机体转化为
muscles and essential organs functioning properly.
维持肌肉和基本器官 正常功能的蛋白质
And the success of a female bear’s pregnancy is tightly
母熊能成功怀孕
linked to those fat stores.
与其脂肪储备密切相关
That’s because bears are one of several mammals
原因在于 熊是一种
whose bodies delay pregnancy until conditions are right.
条件适宜才会怀孕的哺乳动物
After mating takes place in the spring or early summer,
在春天或初夏的交配后
the fertilized embryo hangs around, waiting to implant in the uterine wall in the fall
受精的胚胎要观望一番 等着在秋天进入子宫壁
but only if the female has enough stored fat.
但这只有在母体有充足的脂肪贮存下才会发生
For example, researchers have found that brown bears with less than
举个例子 研究者已发现 体内脂肪少于20%的棕熊
twenty percent body fat didn’t get pregnant even when mating had occurred.
即使已经交配 也不会怀孕
This may have evolved as a way to protect female bears from expending energy
这或许已进化为母熊的一种保护机制
that they don’t have since they have to use their fat reserves as
以避免过度消耗能量 因为母熊需要
both fuel for themselves and their cubs.
靠储备的脂肪 来提供自己和幼崽的养分
As weird as it sounds for them to go to these lengths to give birth
在食物极度短缺期 她们还大费周章生崽
during the months when food is hardest to find,
这听起来令人不解
there are some good reasons that this works for them.
但对熊来说 其中自有一番道理
This strategy allows bears to spend all their time foraging for
利用该策略 在食物丰沛时期
food when it’s most abundant, without pausing to give birth.
熊便可以一直觅食 并不停歇地生崽
And the babies are protected in the den when they’re most vulnerable to predators.
在捕食者面前还弱小不堪的幼崽 则被保护在窝里
So when a bear emerges from the den with little cubs who are seeing the sky for
所以 并非懒散地待在窝里的
the very first time, they weren’t just lazily hanging out inside –
作了大量准备 储存了许多能量的幼崽们
a ton of preparation and energy went into bringing them safely into the world!
在跟着熊出窝时 有生以来第一次看见天空 得以安全来到世上
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