In an unplanned hanging out in summer, Taiwan-based FP writer Vanessa Tsai found her direct encounter with the “Brown Land Crabs” (aka Chestnut crabs, or red-claw crabs) invoking interspecies thinking: must we sustain human survival at the cost of natural survival? 據點駐台作者蔡季妙趁暑假鬆一口氣，隨心的到台南曾文溪口一遊，正值「凶狠圓軸蟹」產卵時節，觸發了「種間思維」對人和自然共生的必要性。
Feature image 主題攝影：CHENG Wei-chun 鄭偉群
Caption 照片說明：Pregnant female crabs climbing up a 40cm-tall vertical surface to cross over to the other side of the dam, the mating spots at the Zengwen River Mouth Wetlands in Tainan. 抱卵的凶狠圓軸蟹，正奮力地攀約四十公分的垂直立面上堤防，前往堤防另一側的曾文溪河口釋幼。
*Please find English translation by Linda Lai right after original Chinese text. Reedited 17 August 1:00pm.
*Photos updated on 18 August 2022.
傳說月圓的夜晚，人與非人的界線會有點鬆動，有點模糊。
七月原本應該是暑假的開端，可以好好地休整自己一整個學期忙亂的生活。然這個暑假一開始，我便得協助學校為期二週的英語營隊。這樣的營隊對我自己而言是新的嘗試，以英文教授學生學習我自己很熟悉的自然領域知識。要考慮學生是否能理解，很需要做些準備，因此神經從期末一路緊繃到營隊結束。
為了讓自己馬上有放假的感覺，營隊結束當天傍晚，月圓之夜，我迅即無縫接軌地到了台南曾文溪口去「放鬆」一下。聽朋友分享、護蟹，覺得該是很有趣的活動，我因此維持一慣的風格，甚麼都沒問，甚麼都不知道的狀況下，跟朋友一起從中部驅車南下，行程上當然先探訪一下南部的濕地，看看各種水鳥，撫慰一下半年來辛勞工作的自己。一路上的走走停停，看出這幾年台灣的社區營造已經進入各個角落，就連以前我覺得很荒涼的海岸邊，現在都都洋溢著一番經營而得的「社區總體」的氣氛。我想，只要當地所有住民 — 是的，當然也包括非人的住民 — 覺得很不錯該就可以了；只要大自然依舊自然，像我這樣偶爾到訪的觀光客，其實沒有置喙的事。重要的是，總體營造，即意味著規劃者對當地「住民」的類別、多樣性和總覽有一定程度的掌握吧？
開著車，一路從傍晚到了黃昏，直接進入夜晚，月亮圓圓的高掛天上，此時已十分接近今天重頭戲上演的地方了。沿著河堤開了好長的一段距離，就這樣帶著雀躍的心情，準備接受來自月圓的能量…
「咦！那是螃蟹嗎？」
『那是螃蟹嗎？』異口同聲。
踩了煞車，很緩慢地經過。「死掉了嗎？」（安靜地繼續向前滑行）
「哇！他動了」
『真的是螃蟹啊！』朋友也訝異起來。
「媽呀！也太大隻了吧？！我們今天要看的螃蟹是這麼大隻的嗎？」
『沒想到可以這麼大。』朋友嚷著。
隔著車窗，看到這樣巨大的螃蟹，原本放鬆的神經也就突然繃緊起來。
「下次還是先做好功課再出門吧。」心裡不斷地這樣提醒自己。無懼則剛，然，無懼其實來自無知，這樣的自己真是太爆笑了。
螃蟹竟然這麼大隻。背甲約有5-8公分吧。除了餐桌上的紅蟳，哪裡還有看過這麼大的螃蟹啊？看來今晚，嚴陣以待了。知道路面上隨時都會有螃蟹出現之後，只能慢慢慢慢地前行，仔細盯緊地面上所有動靜，深怕一個不注意，原本為了護蟹而來，卻成了路殺（roadkill）【注1】殺手那就更搞笑了。
車子終於停下來，我們進入徒步區。真沒想到我和「凶狠圓軸蟹」(Cardisoma carnifex) 【注2】的首次碰面會是如此驚心動魄。走著走著，其實已經深入敵人備戰區！一隻隻巨大的凶狠圓軸蟹，或獨行，或結伴同行，還有成群結隊的。難怪路口需要有「蟹謝讓路」的路標，真的，兇狠的身影隨處可見。然而，當晚最凶狠的莫過於在我的雙腿留下滿滿吻痕的蚊子大兵。真心覺得，月圓之夜，人與非人界線模糊之時，可以在這波攻擊之下好好地存活下來，往後人生應該沒有甚麼難以跨渡的檻了。
微距鏡下的蟹卵，蔡季妙攝 Eggs of the Brown Land Crab viewed under a microscope. Photo by Vanessa Tsai
凶狠圓軸蟹，屬於大型蟹類，頭胸甲紀錄上可寬達十二公分，是台灣體型最大的陸蟹。今年的新聞中【注3】更出現頭胸甲寬達十三點一三的個體。新聞中還提到了，這樣的頭胸甲寬意味著這隻圓軸蟹年齡已經高達六十五歲。其實，我也沒搞懂這換算的依據，也不清楚螃蟹的年紀和人的年紀究竟可如何作比較。眼看密密麻麻的凶狠圓軸蟹在人工的水泥堤防上攀爬，努力地越過堤防到曾文溪口進而走向海口，我著迷了。走訪大自然時，往往發現各種大自然裡的生存法則，讓我感到驚奇。這月圓之時，凶狠圓軸蟹大量湧上馬路準備越過堤防本身不就是不可思議嗎？
凶狠圓軸蟹平常住在防風林裡一到二公尺洞穴內，夜行性，每年七、八月為繁殖高峰【注4】，在月圓前後的日子，總會成群結隊的走向曾文溪口進入海邊，完成她生命中很重要的事，降海釋幼。按今年的紀錄，月圓前後每晚大概有近千隻如此潛行的抱卵的母蟹，爭先恐後的越過堤防。即使在人類築起這麼大的一道水泥堤防之後，母蟹依舊不顧危險穿過馬路、攀爬將近四十公分的垂直立面上到堤防本身，還得繼續走過陡峭的堤防上到最高處，再繼續順著或滑下堤防的另一側而進到曾文溪中。這過程中，當在垂直立面上不去時，我們還可以看到她們成為彼此的墊腳石，像疊羅漢一般，互相幫忙以突破第一道阻隔。接下來，上到堤防本體時，螃蟹走到一半，因為摩擦力不足又滑落回到原處，前功盡棄，那是蠻常見到的。只見她們休息夠了，又繼續跟堤防再次拼搏。那整個晚上，我們從一開始的驚嚇到驚訝，繼而感到愧疚。人類所建的堤防，阻隔了海水倒灌的可能，避免農作物遭受大水的淹沒，卻也讓凶狠圓軸蟹降海釋幼這再也自然不過的行為成為大挑戰，猶如年輕的排灣族人攀爬北大武山【注5】那般地必須。
路殺陣亡的凶狠圓軸蟹，蔡季妙攝 A crab who didn’t make it to her destination. Photo courtesy of Vanessa Tsai
到了現場，才發現其實好多團體都盡力在修正這狀況，希望減少對凶狠圓軸蟹造成的傷害。【注6】例如，有團體便提出過於這段時間封路的申請，讓螃蟹可以較為安全的過馬路；有團體在垂直立面上做了不同的處理 — 掛上麻布袋、噴漿、畫上刻痕、抿石子等等 — 試著讓螃蟹可以更容易的攀上立面；更有團體直接協助螃蟹最後一哩路，帶他們過堤防。我不斷思量著，如果可以在築堤工程開始之前就已通盤考量，即不是只以「人」為本的考量，而是以整個大自然裡萬物的需求來做全面性的思考，是否可以省下後面人們這些看似很有愛心的活動，讓這些善心人的力可以用在更多有意義的事情上？
很多人忙著時，偷閒的坐在橋邊觀察著一切。凶狠圓軸蟹其實並不是柔弱到需要很多的呵護的；她們為了種族的生存，符合自然法則的求生存，在月圓之時，努力地嘗試越過那道高牆。即使這麼艱辛，她們依舊用盡全力在完成必須的事。她們並不柔弱。她們有生存之本，我們人類呢？可否與自然或世界的其他住民合作、協調？
我觀察的過程中，多次在想，是否可以試試把堤岸底端的水泥敲開，沿著堤防開出一道以土壤為底層的溝渠，試著讓馬鞍藤茁壯成長於堤岸上，會是可行作法嗎？曬著月光的我，想像著凶狠圓軸蟹可以攀著馬鞍藤的蔓莖通過垂直立面上到堤防，在堤防上依偎著馬鞍藤的小紫花，那是一幅可愛又溫暖的畫面。圓軸母蟹並不柔弱，她有自己的力氣去完成任務，只要多為她想一點點而已。大部份大自然的生物都是這樣，他們並不柔弱，不需要到人類特別用心呵護便有生存的能力；只要人類在任何開發前，多想到他們一點點點便是。或者，那些有志於開發的人士，在行動前最好先在月圓之時來到這裡「曬曬」月亮又如何？
月光之下，我這個短暫來客並沒能把堤防牆角挖開；在那裡種植馬鞍藤又是否真能成就那幅我想像的畫面也是個未知數。然而，這柔和的月光確實讓人覺得台灣各項工程實施前的說明應該廣納各方意見，找到一個有益於對當地所有人類與非人類的住民的好方案，能測試更多各樣的可能，為這片土地省下所有於事後彌補錯誤的力，多做更值得努力的事情。
『ㄟ，好啊！可以回去了吧？』
「嗯，好啊。可以啊。走吧。」哇！原來月圓之下，這人與非人界線模糊之際，神經緊繃之後的一場夏～之～夢～啊。
Interspecies drama in a full-moon summer evening
螃蟹利用堤防上人行走的階梯當作休息的地方蔡季妙拍攝 Brown Land Crabs resting on the steps while climbing up the embankment for human use. Photo by Vanessa Tsai.
Legend has it that on the night of a full moon, the boundaries between humans and non-humans will become loose and blurred.
My summer break from the hectic semester was supposed to begin in July except that it was delayed for two weeks by my school’s English camp I had to assist. That was a new initiative to enable students to learn natural sciences, which I am familiar with, in the English language. It was a nerve-racking process throughout as it took a lot of preparation to consider whether students can handle.
No sooner had I got out of the camp than I found myself relaxing on a through train from Tai Chung to Tainan on a full-moon night. My friend had been telling me about protecting crabs. Sounds like an interesting activity for a vacation. Knowing very little and not asking much, my usual style, I simply tagged along. Thus began our south-bound car ride. And what a great treat to stop by the Zengwen River Mouth Wetlands to look at the variety of water birds, I told myself. Along the way, I noticed the impact of state-initiated community development projects, which had penetrated rural Taiwan. Coastal areas, which I assumed would be desolate, are now well-formed communities. That’s all fine to me as long as all local inhabitants — by that I mean human as well as non-human ones — receive equal share of care and attention. That is, as long as nature remains natural, the occasional tourist like me has nothing to say . What matters is that the overall planning and construction should mean that the planners have comprehensive knowledge of the taxonomy and demographics of the local “inhabitants.” Is that really the case? I wondered.
We were driving all the way from late afternoon to dusk and into the depth of evening with the full moon hanging high in the sky. By then, we were very close to where the night’s main drama took place after covering a long distance along the river bank. I was so excited, my energy charged by the full moon…
“Huh! Is that a crab?”
“Is that a crab?” in unison, looking out from the car.
We hit the brakes and passed very slowly. “Dead?” (We continued to glide forward quietly.)
“Wow! It’s moving.”
“It’s really a crab!” My friend was also surprised.
“Mommy! It’s too big, isn’t it?! Are the crabs we’re going to see today this big?”
“I didn’t expect them to be this big,” cried my friend.
Watching these huge crabs from behind the window, my nerves tightened up altogether.
“Next time, you’d better do your homework before setting out on a trip,” I told myself in my mind. Fearlessness is courage; but fearlessness also comes from ignorance. I found myself hilariously ridiculous.
These crabs are truly big. Their back armour is about 5-8 cm. Other than the Giant Mud Crab (scylla serrata) served on the dinner table, where have I seen such a big crab? It was a big time to watch out that evening, we thought. Knowing that they would appear on the road from anywhere any time, we could only move forward slowly with great caution, paying close attention to all movements on the ground. I was so worried that our intention to protect the crabs might turn out to be a roadkill [ Note 1] It wouldn’t be funny to turn ourselves into killers, would it?
The car finally stopped and we entered the hiking area. I had no idea that my first encounter with the Cardisoma carnifex [Note 2] would be so thrilling. Walking on and on, we gradually penetrated into the enemy’s “preparation zone”! Brown Land Crabs (BLC) were moving everywhere, alone, accompanied, or in groups. No wonder there was this road sign that screamed “give way to the crabs” at every intersection. Indeed, BLC shadows were everywhere. However, the most vicious [a qualifier of the crabs in their Chinese name only] thing of the night was the army of mosquitos who left my legs full of hickeys. It feels strangely real that on the night of the full moon, the boundaries between humans and non-humans are blurred. If anyone could survive the wave of attacks we had that evening, there should be no more difficult barriers in life to cross in future.
The Brown Land Crab belongs to the large crab class, and the head and breastplate can be recorded as wide as 12 cm. It is the largest terrestrial crab in Taiwan. In this year’s news [Note 3], an individual BLC with a cephalothorax as wide as 13.13 was sighted. It was also mentioned in the news that such a wide head and breastplate means that this individual crab could be compared to a sixty-five-year-old human. I actually do not understand the comparison or how the conversion works. I was more fascinated when I saw the density of BLCs covering the ground and climbing upward on the artificial concrete embankment, struggling to cross over to the other side of the Zengwen River Mouth, which then connects with the ocean in the east. In many of my former field visits to study nature, I often noticed all kinds of amazing laws of survival. In this trip, watching the BLCs struggling rounds after rounds to overcome the embankment was like watching magic illumined by the full moon. It’s almost inconceivable to the human mind!
The Brown Land Crab usually lives in a cave of one to two meters in the windbreak forest. It is nocturnal. The peak breeding season is in July and August every year [Note 4]. Once a month before and after the full moon, the pregnant female crabs will march in group into the sea through the Zengwen River Mouth to complete the most important task of their life — to release the young. According to this year’s official records, there are about a thousand female crabs cradling eggs like this, scrambling to cross the embankment. Even after humans built such a large concrete embankment, the female crabs still cross the road despite all kinds of precarity, to climb nearly 40 centimeters of vertical elevation to the embankment itself, before continuing to walk over the steep embankment to the highest point, where they follow one another or slide down to the other side of the embankment into the Zengwen River. One must not miss the many fine details of the entire process. When it is too hard to climb straight up the vertical façade, some of the crabs become stepping stones for each other, like stacking Arhats, helping each other to break through the first barrier. Then, when they are reaching the main body of the embankment, it is quite common that some crabs slip back to its original place due to insufficient friction, and they would have to start all over again. Some, having had enough rest, would continue to fight against the dike. That night, we went from shock to surprise and then to guilt. The dikes built by human beings indeed successfully block seawater’s back-flow and prevent crops from being submerged by floodwaters. But they also create a humongous obstacle for the BLCs to descend into the sea to release their young, a natural cycle that is now made a weighty task. I cannot help thinking of the young Paiwan people’s necessary, or inevitable, plight to climb the sacred Taimu Mountain, at least once in their life time, to pay respect to their ancestral origin, so the motto goes. [Note 5]
凶狠圓軸蟹，身上的記號是志工團體避免重複數算用的。蔡季妙拍攝 The crabs are “marked” by people from voluntary organisations for the purpose of counting (Vanessa Tsai)
On site through our journey, I found that many groups have been making attempts to correct the situation, hoping to reduce the damage to the BLCs. [Note 6] Some groups, for example, have proposed to the local authorities to impose road closures during this period so that crabs can cross the road more safely. Some groups have applied special treatments on the vertical wall of the dyke, such as hanging burlap bags, spraying grout on the surface, engraving marks, sipping stones to roughen the surface and so on — to make it easier for the crabs to climb. Some groups directly assist the crabs on the final segment of the journey by taking them over the embankment. I kept asking: wouldn’t it be possible to save money if the embankment project had been more comprehensively considered, that is, not just based on people-oriented purposes, but also on the needs of all things in nature? Wouldn’t the resources involved in people’s caring efforts be channeled more effectively into other meaningful purposes?
Hopefully, we would all feel compelled enough at times to break away from our daily burdens to look around and observe. As I do it this time, I realise the BLCs are no weak living things, nor do they need a lot of care from us. They are capable of the survival of their race, and they evolve with skills to cope with the laws of nature: so the full moon is there to unveil their survival, and we see the pregnant female crabs collectively cross the human-made high wall. What they do is simply to respond to nature’s call. But what about our thoughtful collaboration?
An idea has been brewing in my mind, which I think may work. Why don’t we knock off parts of the cement at the bottom of the embankment and create a ditch with soil as the bottom layer along the embankment? This would allow saddle vines to thrive on the embankment. Would it be feasible or practical? As I basked in the moonlight that evening, I imagined a school of female terrestrial crabs climbing up the vine stems of the saddle vine to the embankment through the vertical façade, then on the embankment nestled the vine’s little purple flowers. What a lovely and warm picture. The female Brown Land Crab is not weak, she has her own strength to complete the task, as long as we think a little more for her. In fact, most living things in nature are like that — they have the ability to survive without special care from human beings, as long as human beings think about them a little bit more before advancing their developmental grand plan. Perhaps for those who do have a plan for progress, it wouldn’t be a bad idea to come here to be “bathed” by the moon before taking action.
凶狠圓軸蟹與馬鞍藤共存的環境蔡季妙拍攝 Vanessa Tsai captured the Brown Land Crab and the saddle vine cohabiting.
Even with the moon’s shine, I, a short-term visitor, would not be able to dig a ditch at the foot of the dike; I am also not sure whether planting saddle vines is a sound idea. However, one thing must be making sense: the pre-implementation rationales of large-scale community projects should be more robust, and that the planners in Taiwan should base their decision on a wider range of opinions, in order to find a good plan that is beneficial to all local human and more-than-human residents. Planners should also allow time for feasibility tests, thus to streamline and save potential waste of resources.
“ㄟ, okay! Shall we go home now?”
“Um, okay. Okay. Let’s go.”
Wow! The power of the full moon remains mesmerising. What a mid-summer night’s dream in which the human and the more-than-human cross over.
連人站在上面都顯得費力的堤防蔡季妙拍攝 Even humans would feel exhausted climbing up the steep and tall steps on the staircase’s embankment. Photo by Vanessa Tsai.
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NOTES 註：
*1：路殺（roadkill）道路上的動物因機動車輛的碰撞或碾軋而死亡的現象（引用維基百科解釋）Roadkill is a scenario in which animals are killed on the road due to car or machine crashes. (Wikipedia)
*2：Cardisoma carnifex is a species of terrestrial crab found in coastal regions from the east coast of Africa and the Red Sea across the Indo-Pacific to the Line Islands and the Tuamotu Archipelago. The range includes parts of northern Australia and the Cocos Islands. (Wikipedia)
*3：source 資料來源：https://reurl.cc/9pGG0n
*4：source 資料來源：https://reurl.cc/vWWkey
*5：排灣族是分佈於台灣南部為主的原住民族之一，北大武山是該族的聖山。目前北大武山徑以前是獵人必經的路徑，因統治者的政策（https://reurl.cc/D3369e）而今族群已從深山區移居淺山區多年。生活樣態轉變，很多年輕一代的族人並未到訪過北大武山，因此族群裡對年輕一代呼喊「一生必走一次北大武」。然，有些年輕族人已不太能負荷這樣的活動。The aboriginal Paiwan population is distributed over the southern part of Taiwan. Taimu Mountain’s north is considered the Paiwanese’ sacred mountain. Their mountain paths used to be the main routes for hunters. Various political administrations have gradually forced the Paiwanese out of the deep mountains into the more accessible mountain areas, and many younger-generation Paiwanese have migrated and never had a visit to the Taimu Mountain, thus the call “once in a life time must a Paiwanese visit the Taimu. But it is easier to say than climb the mountains, which is a taxing activity to most young people.
*6: An example from an 18 July 2022 report: https://www.icrt.com.tw/info_details.php?mlevel1=6&mlevel2=12&news_id=228261&reUrlAddr=L25ld3NfZGF0YWJhc2UucGhwP21sZXZlbDE9ZWhzeXNsb2NkcnN2YXF4JnBhZ2U9MzU=
