| Number of coconut crabs on Green Island decreasing rapidly They said that with the increase of business activities on the island, the number of coconut crabs has decreased rapidly, dwindling to around 80 in the latest census three years ago. They attributed the dramatic decrease in the number of crabs to the impact from tourism development, accidental killing of the crabs by motorcycles which are a major form of transportation on the island, and people catching the crabs for different purposes. The Biodiversity Research Center at Academia Sinica, the top research institute in Taiwan, in a census three years ago estimated that only around 80 coconut crabs were left on the island. Since then, the researchers, the Coast Guard and locals scholars of history and culture have adopted various protection measures,educational research and ecotourism approaches to try to rehabilitate the coconut crabs, although the efforts can hardly be seen as keeping pace with the rate of destruction. The experts said that with the rapid development of tourism, a large number of land development projects has destroyed the habitats of the crabs, and the flood of tourists has also impacted on the existence of the crab species. To deal with the problem of the crabs being accidentally run over by motorcyclists, the experts built an "ecological corridor" around the Green Island lighthouse three years ago in a bid to keep tourists at a distance from the crabs, but the results have not been significant. The coconut crab, or birgus latro, gets its name for its ability to crack coconuts with its strong pincers in order to eat the meat. The crab is the only species of the genus Birgus. The crabs were once populous on Green Island, which is located 33 kilometers off Taitung. The crabs were often caught for use in religious ceremonies as sacrifices, to be given to children as pets, or to be eaten by women who had just given birth, because of the health benefits attributed to eating the meat. (By Lilian Wu) |
我的台灣朋友看到聖誕島這麼多螃蟹時，問我的第一個問題都是：「好不好吃？」
很不好意思地去問了當地居民，他們的回答更讓我覺得內疚了：「如果要問好不好吃，那麼大隻的椰子蟹，肉多肥美，非常好吃。不過我們不會吃牠，因為一來牠們是雜食動物，什麼都吃，連爛掉的果實跟動物屍體都吃，所以不乾淨；二來政府已經列為保育類動物，這些robber crab要長到跟椰子一樣大都要40-60年，我們幾秒鐘就可以把牠們殺了，如果抓來吃，沒幾年就看不到螃蟹了。我看紀錄片，你們台灣不是以前也有robber crab，結果現在都被吃光了嗎？」
說實話，聖誕島上並沒有什麼美不勝收的風景，當地到處都有的椰子蟹跟海裡喜歡跟漁人玩的豆腐鯊，台灣其實也找得到（應該說「吃得到」吧？！），只是我唯一看過的豆腐鯊，是在基隆街頭的漁市場內，被切成幾大塊，擺在大冰塊上待價而沽；而椰子蟹，更是只有在書裡看過而已。
豆腐鯊/ 鯨鯊 (圖片來源/ http://www.whale-shark.org )
在聖誕島去潛水，當地人就會跟你說「可以去跟鯊魚玩喔！」，他們口中的鯊魚，就是世界上最溫馴的豆腐鯊（whale shark，又稱鯨鯊），這種鯊魚從來不咬人，有時還會跟船隻玩耍，偷偷地輕輕撞一下船，然後玩躲貓貓似地潛在船底讓人找不到，當地人從來沒想過要殺了這種跟海豚一樣可愛的動物，反而還教導觀光客如何與牠們和平相處。
而椰子蟹在這裡也是天堂，除了到處都有的椰子可吃，還有居民為了不讓牠們亂吃，每天都去餵吐司，久而久之，每天一早，許多大大小小的椰子蟹就會爬出來等著吃吐司，紫色的、藍色的外殼，似乎只有在動物園裡，才能看到這些有著奇異造型跟特殊生態的動物。
椰子蟹學名為Birgus latro，英文稱之為coconut crab或是robber crab。源自於海洋的動物，牠和其它原本在海中生活，後來遷移到陸地的動物一樣，必須面臨呼吸以及水分流失的問題。因此牠的鰓腔內壁有許多血管叢生，可以幫助呼吸；有甲質化的外殼；並且棲息於濕度較高，具有能遮蔽日曬的掩蔽物及洞隙，土質鬆軟以利其挖洞蛻皮，以及有充足食物的地區，所以能長期棲息在陸地生活，到了繁殖季節才回到海洋裡產卵。
椰子蟹只有在幼蟹階段還會背著螺殼，當孵化後經過1-2年，頭胸甲長到1~1.5公分，牠就擺脫了螺殼，直接用堅硬的外殼來保護腹部。椰子蟹的身體兩側是對稱的，這樣大而結實的個體，常常被誤認為是螃蟹，但牠其實是貨真價實的寄居蟹。
就像當地人說的，椰子蟹長得很慢，兩歲大的椰子蟹也才約兩三公分，然後類似烏龜脫皮一樣的蛻殼過程，慢慢長大，所以要長到跟椰子差不多大的椰子蟹，年紀都比我們還老了，據說最大可以長到7公斤重，但那已經是「蟹瑞」了，也因如此，我們又於心何忍去殺死那些好不容易才長大的椰子蟹呢？
在台灣，曾經綠島、蘭嶼一帶都是椰子蟹出沒的地區，近年觀光客大量進入綠島後，椰子蟹的生存就受到嚴重威脅。聽說椰子蟹好吃又補身，所以許多觀光客都指名來吃，大量捕殺的結果，這兩年在綠島已經幾乎看不太到椰子蟹的蹤跡，而許多保育人士曾經試著想用人工培育的方式來保護椰子蟹，可是往往都是失敗收場。這也讓椰子蟹的未來，變得更不樂觀。
同樣都是華人，什麼時候，我們台灣人才會更有保護地球大自然的觀念，而不再是什麼都吃的野蠻民族？我也很想哪一天，我只要到綠島去玩，就可以跟豆腐鯊一起游泳，跟椰子蟹一起在路上散步？
延伸閱讀:
綠島永續行動資訊網-認識椰子蟹
椰 子 蟹 -背負第一美味蟹的原罪
落實椰子蟹的保育
自由新聞網-《專題報導》大啖豆腐鯊 舉世唯台灣
生命力新聞-豆腐鯊逐年減少 台灣難辭其咎
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攝影/ Ted Wang