營養不良還想嚇唬人！這就是大熊貓黑白相間的原因？

憨態可掬的大熊貓為什麼只有「黑白照片」？這其實是生物研究中的難題。美國研究人員日前在新一期《行為生態學》雜誌網路版上發表論文解答，大熊貓的黑白色有兩種功能：偽裝和交流。

領導研究的美國加利福尼亞大學戴維斯分校教授蒂姆·卡羅介紹說，生物學界長期存在的一個問題就是如何理解大熊貓身上的黑白色，這並不容易回答，因為其他哺乳動物長得都不是這樣的，所以很難通過類比來解釋。

該校和加利福尼亞州立大學長灘分校的研究人員根據皮毛顏色深淺將大熊貓的身軀劃分成不同區域，並與狗、貓、熊等１９５種食肉動物以及熊科動物的３９個亞種進行比較，來尋找關聯性並確定其功能。

研究人員通過比較發現，大熊貓的臉、脖子、肚皮和臀部之所以是白色的，是因為這能幫助它們在積雪的棲息地躲藏；而四肢之所以是黑色的，是因為這能幫助它們將自己躲藏在陰影里。

研究人員認為，大熊貓長成這樣源於其消化能力較弱，只能以竹子為食而不能吃更多種植物。它們也無法像有些熊那樣在冬天存儲多餘的脂肪來冬眠。它們必須終年活動，長途跋涉去覓食，其棲息地變化也很大，從雪山到熱帶森林都有。

不過，大熊貓的頭部配色不是為了偽裝躲開捕食者，而是起到交流作用。它們黑色的耳朵表達一種「兇殘」的感覺，可以警告捕食者；而黑眼圈有助於同類間互相識別，或者向同類競爭者加以警告。

Scientists have thrown up plenty of potential reasons for the contrasting colors of the giant panda bear. Could they be for stealth, regulating temperature or a warning to potential predators? Researchers now believe they know the reasons behind the iconic black and white patches: a need for camouflage combined with a need to communicate.

The scientist that led the research, Tim Caro, has some experience in uncovering the secrets behind another animal"s distinctive coloring. A professor at University of California, Davis, in 2014 he published a paper in the journal Nature Communications, revealing that the reason zebras have stripes is to deter biting flies. He arrived at this conclusion by reviewing literature on other mammals in the horse family and found that striped species occurred in locations where biting flies were abundant.

But the issue with tackling the same problem in the panda bear is that there is no animal like it; it stands alone as a black-and-white outlier among mammal species, which makes comparisons difficult. But the team overcame this by breaking down the different parts of the body and treating them as independent areas.

Through this method, the team compared patches of fur from the panda"s body to the dark and light coloring of 195 other carnivore species and 39 related bear sub-species. They then examined associations with the various hair colorings and the animal"s environment to work out what purpose they served.

The results led them to conclude that the majority of the panda"s body, including its face, neck, belly and behind, is white to help it blend into snowy habitats. Its arms and legs meanwhile, are black to help it hide in the shade. Interestingly, the black markings on the head seem to have nothing to do with camouflage, but rather are used for communication. The dark ears may help them seem fierce when the time is right, as a warning to predators, while the dark patches around the eyes might be used for communication, helping pandas recognize one another or signal aggression.

The team suggests that pandas evolved their two-tone appearance due to their poor diet of bamboo, which meant that they were never able to store enough fat to go dormant during the winter like some bears. So because they had to be on the move year-round, they had to be able to hide in a variety of habitats ranging from snowy mountains to tropical forests.

"This really was a Herculean effort by our team, finding and scoring thousands of images and scoring more than 10 areas per picture from over 20 possible colors," said co-author Ted Stankowich, a professor at California State University, Long Beach. "Sometimes it takes hundreds of hours of hard work to answer what seems like the simplest of questions: Why is the panda black and white?"

The team"s research was published in the journal Behavioural Ecology.

Source: University of California, Davis via EurekAlert

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