譯/李京倫 核稿/樂慧生
為何帝王斑蝶愈來愈少？
Western monarch butterflies spend their winters in Pismo Beach and other sites on the central California coast. A few months later, they breed in the Central Valley and as far north and east as Idaho.
美國西部帝王斑蝶會在加州中部沿岸皮斯摩海灘市等地過冬。幾個月後，會在加州中部「中央谷地」，以及往東北方向最遠可到愛達荷州的地區交配。
But where they go in between remains an open question.
不過，這中間的空檔帝王斑蝶去了哪裡，仍沒人知道。
Now, a group of researchers wants the public's help to solve that mystery.
現在，一群研究人員希望民眾幫忙解開這個謎。
They would like anyone who spots a monarch north of Santa Barbara this spring to snap a quick picture. The researchers — from Washington State University, Tufts University, the nonprofit Xerces Society for Invertebrate Conservation, and the University of California, Santa Cruz — need photographic evidence, a date and a location to confirm where the monarchs might be living. (Photos and information can be emailed to monarchmystery@wsu.edu or uploaded on the iNaturalist app.)
他們希望，今年春天凡是在加州聖塔芭芭拉市以北發現帝王斑蝶的人，都拍下快照。這群研究人員來自華盛頓州立大學、塔夫茨大學、非營利組織澤西斯無脊椎動物保育協會和聖塔克魯茲加州大學，他們需要照片、拍攝日期和地點，用以確定帝王斑蝶的棲地。（照片和資訊可以用電郵寄到monarchmystery@wsu.edu，或用iNaturalist app上傳。）
"Something's going on in early spring," said Cheryl Schultz, a professor at Washington State University, in Vancouver.
加拿大溫哥華市華盛頓州立大學教授雪柔．舒茲說：「有某種事情在早春發生。」
Researchers know that winter survival isn't the issue in the short term, she said. But they don't know whether the monarchs are not making it to breeding sites, not finding plants to nourish them along the way, or not able to find mates.
舒茲說，研究人員知道，帝王斑蝶安度冬天短期內不是問題，研究人員不知道的是，帝王斑蝶是否到不了交配的地點，是否在沿途找不到植物供給營養，是否找不到交配對象。
The Western monarch population, which lives west of the Rocky Mountains, stood in the millions in the 1980s. In 2017, an annual count found 200,000 butterflies. In 2018, the tally fell to about 30,000 — a figure that held steady last year, said Elizabeth Crone, a biology professor at Tufts University, in Medford, Massachusetts.
美國西部的帝王斑蝶棲息在洛磯山脈以西，在1980年代多達數百萬隻。2017年的年度調查顯示還有20萬隻。2018年剩下大約3萬隻。麻州梅德福市塔夫茨大學生物學教授伊麗莎白．克隆說，去年也差不多是這個數量。
The monarch's decline is part of a larger trend among dozens of butterfly species in the West,said Matt Forister, an insect ecologist at the University of Nevada.
內華達州雷諾市內華達大學昆蟲生態學者佛瑞斯特說，帝王斑蝶數量減少，是美西數十種蝴蝶數量減少的更大趨勢的一部分。
Research pins the loss of Western butterflies on a variety of factors, including development, climate change, farming practices, and the widespread use of pesticides by farmers and on home and business lawns, Forister said.
佛瑞斯特說，研究人員認為美西蝴蝶數量減少有多種原因，包括開發、氣候變遷、農作方式，以及農民、家庭和商業草坪廣泛使用農藥。
For example, Schultz said farms used to have rough, weedy borders that were great breeding grounds for the types of plants that monarchs love. Newer farming practices have pushed crops to the edge of the fields, leaving no room for these weedy margins, she said.
舒茲說，例如先前農場邊緣往往未開墾且雜草叢生，是帝王斑蝶喜愛的植物種類的沃土。她說，比較新穎的農耕方式會把作物種到農場邊緣，不讓這些邊緣有長出雜草的空間。
Another factor, she said: Some homeowners, eager to attract monarchs, have planted tropical milkweed. Although the butterflies will feed on them, these plants tend to spread disease because they don't drop their leaves, Schultz said, which may be contributing to the declining monarch population. Native milkweed supports the population without this risk, she said.
舒茲說，另一因素是，有屋主想吸引帝王斑蝶，就種了熱帶乳草。雖然帝王斑蝶會來吃，但乳草不掉葉子，容易傳播疾病，可能造成帝王斑蝶數量減少。她說，本地乳草能餵養帝王斑蝶，卻沒有這種風險。
※說文解字看新聞 李京倫
帝王斑蝶是大型蝴蝶，有醒目的橘、黑、白色斑紋極易辨認。成熟後翼展可達13公分。本文探討美國西部帝王斑蝶為何從數百萬隻減少到三萬隻左右。
population在本文中指某個範圍內某個物種的總數，急遽減少可以說rapid/sharp/steep/dramatic decline，逐漸減少則可以說steady/gradual/long-term decline。要阻止總數減少，可以說stop/halt a decline，復育有成則可說reverse a decline。
pin原意是別針、大頭針，尤其是固定布料用的，或釘、楔、銷、栓等用於固定的細長木頭或金屬。本文的pin something on為非正式用語，是「把某事歸咎於…」。最近常出現在新聞中的pull the pin，則是停止做某事的意思，如：Canada became the first country to pull the pin on Tokyo 2020 Olympics due to the coronavirus pandemic.
