At a South African nature preserve where Miya Warrington， a conservation ecologist at the University of Manitoba in Canada， and her colleagues study Cape ground squirrels， the maximum daily temperature has increased by about 2.5°C in just 18 years. The animals have evolved a quiver of tactics to tolerate the regions sweltering heat， says Warrington.

Sprawling flat on the ground in a pose called splooting helps the animals shed heat from their less furry undersides. The squirrels take shady respites under their bushy tails， which they curl above their heads like tiny parasols. When its really hot， the fossorial mammals retreat to their burrows to cool off. But Warrington warns that， even with all these options for keeping cool， “still they could be at the limits of their tolerance” due to the climatic shift.

在南非的一個自然保護區(qū)，加拿大曼尼托巴大學的生態(tài)保護學家米亞·沃靈頓和她的同事在研究南非地松鼠時發(fā)現(xiàn)，這里的日最高氣溫在短短18年內(nèi)已經(jīng)上升了約2.5攝氏度。沃靈頓說，這里的動物已經(jīng)進化出一系列耐受這個地區(qū)炎熱氣候的生存之道。

動物以一種叫“板鴨趴”的姿勢趴在地上，可以幫助它們從皮毛較少的腹部散發(fā)熱量。松鼠把尾巴卷在頭頂上，像小遮陽傘一樣，在自己濃密的尾巴下乘涼。當天氣很熱的時候，這些窩棲哺乳動物會躲在它們的洞穴里乘涼。但沃靈頓發(fā)出提示，盡管有這些保持涼爽的方法，但由于氣候的變化，“它們?nèi)匀豢赡芴幵谀蜔岬臉O限”。

That intense pressure could be why their bodies have begun to change shape， Warrington says. She found that， over the course of just under two decades， the squirrels already incredibly large hind feet have grown. Meanwhile， their spine lengths have become ?shorter.

And the Cape ground squirrel isnt the only animal that appears to be shape-shifting in response to climate change. As scientists accumulate more evidence that many species bodies are undergoing subtle changes over a relatively short period of time， it remains unclear whether their adaptations can keep ahead of spiking temperatures—and how close they may be to a breaking point.

Youngflesh， an ecologist who is not involved in the study， sought to determine whether bird body sizes shrank temporally as climate change has driven hotter weather in areas throughout North America. “To record this change in so many species over such a short period really suggests that there is something global affecting all these birds—and climate change is what makes sense，” he says.

沃靈頓說，這種巨大的（環(huán)境）壓力可能是它們的身體開始改變形狀的原因。她發(fā)現(xiàn)，在不到20年的時間里，這些松鼠原本非常大的后腳變得更大了。與此同時，它們的脊柱長度反而縮短了。

南非地松鼠并不是唯一的因氣候變化而改變體形的動物?？茖W家們搜集了更多的證據(jù)，證明許多物種的身體在相對較短的時間內(nèi)發(fā)生了微妙的變化，但它們的適應能力是否能在氣溫飆升之前保持下去，以及它們離崩潰點有多近，科學家們尚不清楚。

沒有參與這項研究的生態(tài)學家楊弗拉什試圖查明，由于氣候變化導致整個北美地區(qū)的天氣變熱，鳥類的身體尺寸是否會隨之暫時性地縮小。“在這么短的時間內(nèi)記錄到這么多物種的這種變化，確實表明有一些全球性的因素影響著所有這些鳥類——氣候變化就是這個影響因素?！彼f。

Word Bank

evolve /i'v?lv/ v. 進化

The three species evolved from a single ancestor.

retreat /r?'tri?t/ v. 逃避；躲避

subtle /'s?tl/ adj. 不明顯的；微妙的

shrink /?r??k/ v.（使）縮小