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  • Translator: Joseph Geni Reviewer: Morton Bast

    翻訳: Chiaki Takeuchi 校正: Misaki Sato

  • This is poo,

    これはフンです

  • and what I want to do today is share my passion

    今日はフンに懸ける私の思いを

  • for poo with you,

    共感して頂きたいと思います

  • which might be quite difficult,

    できなくても構いません

  • but I think what you might find more fascinating

    しかしこの小さな生物と フンの関係には

  • is the way these small animals deal with poo.

    興味を持てるのでは ないでしょうか

  • So this animal here has got a brain

    この生物の脳は

  • about the size of a grain of rice, and yet it can do things

    米粒ほどの大きさです しかし人間なら

  • that you and I couldn't possibly entertain the idea of doing.

    試みることもないことを 彼らはするのです

  • And basically it's all evolved to handle its food source,

    つまり彼らの食糧源である

  • which is dung.

    フンの扱い方です

  • So the question is, where do we start this story?

    さて何から話しましょう?

  • And it seems appropriate to start at the end,

    やはりここはお尻からが いいでしょう

  • because this is a waste product that comes out

    これは他の動物が出す 排泄物ですが

  • of other animals, but it still contains nutrients

    まだ栄養が残っています

  • and there are sufficient nutrients in there

    フンコロガシが生きていくのに

  • for dung beetles basically to make a living,

    十分な量の栄養素です

  • and so dung beetles eat dung, and their larvae

    彼らはフンを餌とし その幼虫も

  • are also dung-feeders.

    またフンを食べます

  • They are grown completely in a ball of dung.

    フンだけを餌にして 成長するのです

  • Within South Africa, we've got about 800 species of dung beetles,

    南アフリカには800種の フンコロガシがいます

  • in Africa we've got 2,000 species of dung beetles,

    アフリカ全体では2000種

  • and in the world we have about 6,000 species of dung beetles.

    世界では6000種です

  • So, according to dung beetles, dung is pretty good.

    彼らにとってフンは 相当のごちそうです

  • Unless you're prepared to get dung under your fingernails

    指でフンをほじくれなければ

  • and root through the dung itself, you'll never see

    フンコロガシ種の9割は

  • 90 percent of the dung beetle species,

    お目にかかれません

  • because they go directly into the dung,

    彼らはフンの奥に

  • straight down below it, and then they shuttle back and forth

    入り込み 地上のフンと

  • between the dung at the soil surface

    地中の巣との間を

  • and a nest they make underground.

    何度も往復するからです

  • So the question is, how do they deal with this material?

    では 彼らはフンを どう扱うのでしょう?

  • And most dung beetles actually wrap it into a package of some sort.

    大半は何かしらの形にまとめます

  • Ten percent of the species actually make a ball,

    1割方は フンをボールのようにして

  • and this ball they roll away from the dung source,

    元のフンから離れた 場所へと転がし

  • usually bury it at a remote place away from the dung source,

    地中に埋めます

  • and they have a very particular behavior

    彼らは独特の行動を取りますが

  • by which they are able to roll their balls.

    その行動によってフンが転がせるのです

  • So this is a very proud owner of a beautiful dung ball.

    ここに自慢げなフンの持ち主がいます

  • You can see it's a male

    オスです

  • because he's got a little hair on the back of his legs there,

    足の後ろに毛が生えていますからね

  • and he's clearly very pleased about what he's sitting on there.

    彼はこの美しいフンの玉に ご満悦のようです

  • And then he's about to become a victim

    ところが悲劇です

  • of a vicious smash-and-grab. (Laughter)

    卑劣な強盗の 犠牲者となりました

  • And this is a clear indication

    この行為はフンが貴重な

  • that this is a valuable resource.

    食糧源であることの表れです

  • And so valuable resources have to be looked after

    貴重な食糧源は特別な方法で

  • and guarded in a particular way, and we think

    守る必要があります だからフンを遠くに

  • the reason they roll the balls away is because of this,

    転がすのではないでしょうか?

  • because of the competition that is involved

    フン獲得の競争が

  • in getting hold of that dung.

    激しいからです

  • So this dung pat was actually -- well, it was a dung pat

    このフンの塊--もはや過去形ですね

  • 15 minutes before this photograph was taken,

    この写真を撮影する15分前は塊でした

  • and we think it's the intense competition

    この激しい競争こそフンコロガシが

  • that makes the beetles so well-adapted

    フンを転がすに至った

  • to rolling balls of dung.

    理由ではないかと思うのです

  • So what you've got to imagine here is this animal here

    ではこの生物がアフリカの

  • moving across the African veld.

    草原を横切る姿を想像して下さい

  • Its head is down. It's walking backwards.

    頭を下に 後ろ向きに歩いています

  • It's the most bizarre way to actually transport your food in any particular direction,

    食糧の運び方として これ以上ないほど突飛です

  • and at the same time it's got to deal with the heat.

    しかも熱との戦いもあります

  • This is Africa. It's hot.

    アフリカは暑いです

  • So what I want to share with you now

    ではここで私と同僚が行った

  • are some of the experiments that myself and my colleagues

    実験についてお話します

  • have used to investigate how dung beetles

    フンコロガシは運搬と熱に

  • deal with these problems.

    どう対処しているのでしょう

  • So watch this beetle,

    このフンコロガシを見てください

  • and there's two things that I would like you to be aware of.

    二つの点に注目して下さい 一つは

  • The first is how it deals with this obstacle

    置かれた障害物に対する

  • that we've put in its way. See, look, it does a little dance,

    対処法です ちょっと踊りましたね

  • and then it carries on in exactly the same direction

    そして最初に向かっていた方向と

  • that it took in the first place.

    全く同じ方向に歩いていきます

  • A little dance, and then heads off in a particular direction.

    一瞬踊ってから 目的の方向へと進みます

  • So clearly this animal knows where it's going

    彼らは行き先が 分かっているのです

  • and it knows where it wants to go,

    行きたいところがわかっています

  • and that's a very, very important thing,

    これは非常に重要なことです

  • because if you think about it, you're at the dung pile,

    例えば自分が大きなフンの塊の中にいて

  • you've got this great big pie that you want to get away from everybody else,

    ご馳走を独り占めしたい 遠くに運びたいわけです

  • and the quickest way to do it is in a straight line.

    直進するのが 一番手っ取り早いですよね

  • So we gave them some more tasks to deal with,

    そこで私達はこの子に 更に課題を与えました

  • and what we did here is we turned the world

    彼の足元を回転させたのです

  • under their feet. And watch its response.

    彼の反応に注目して下さい

  • So this animal has actually had the whole world

    彼の世界は足元で今回転しました

  • turned under its feet. It's turned by 90 degrees.

    90度回転したのです

  • But it doesn't flinch. It knows exactly where it wants to go,

    しかし全く動じません 行きたい方向に

  • and it heads off in that particular direction.

    再び向かっていきます

  • So our next question then was,

    ではどうやって彼らは

  • how are they doing this?

    行き先を認識しているのか?

  • What are they doing? And there was a cue that was available to us.

    何をしているのか?  私達は気がつきました

  • It was that every now and then they'd climb on top of the ball

    彼らは時々ボールの上に登るのです

  • and they'd take a look at the world around them.

    そして辺りを見回します

  • And what do you think they could be looking at

    ボールの頂上に登って

  • as they climb on top of the ball?

    彼らは一体何を見ているのでしょう?

  • What are the obvious cues that this animal could use

    動物が利用できる手掛かりは

  • to direct its movement? And the most obvious one

    何でしょう? 一番分かりやすいのは

  • is to look at the sky, and so we thought,

    空でしょう では空の何を

  • now what could they be looking at in the sky?

    見ているのでしょう?

  • And the obvious thing to look at is the sun.

    空と言えば太陽です

  • So a classic experiment here,

    そこで典型的な実験をしました

  • in that what we did was we moved the sun.

    太陽を動かしたのです

  • What we're going to do now is shade the sun with a board

    板を使って太陽を遮ります

  • and then move the sun with a mirror

    そして鏡を使って全く違う

  • to a completely different position.

    位置に太陽を動かします

  • And look at what the beetle does.

    フンコロガシの反応を見てください

  • It does a little double dance,

    少し踊って

  • and then it heads back in exactly the same direction

    元の方向と全く同じ方向へ

  • it went in the first place.

    歩いていきます

  • What happens now? So clearly they're looking at the sun.

    彼らが太陽を見ていることが 明らかになりました

  • The sun is a very important cue in the sky for them.

    彼らにとって太陽は 重要な手掛かりなのです

  • The thing is the sun is not always available to you,

    でもいつも太陽があるとは限りません

  • because at sunset it disappears below the horizon.

    日没後は水平線の下に 隠れてしまいます

  • What is happening in the sky here

    空には私達には見えない

  • is that there's a great big pattern of polarized light in the sky

    偏光の大きなパターンがあります

  • that you and I can't see. It's the way our eyes are built.

    人間の目では感知できません

  • But the sun is at the horizon over here

    しかし太陽は 水平線上にあります

  • and we know that when the sun is at the horizon,

    太陽が水平線上にある時は--

  • say it's over on this side,

    例えばこちら側にあるとすると

  • there is a north-south, a huge pathway across the sky

    南北に大きな帯状の

  • of polarized light that we can't see

    偏光パタ―ンができます 人間には見えません

  • that the beetles can see.

    でもフンコロガシには 見えるのです

  • So how do we test that? Well, that's easy.

    ではそれを証明しましょう

  • What we do is we get a great big polarization filter,

    大きな偏光フィルターを用意します

  • pop the beetle underneath it, and the filter is at right angles

    その下にフンコロガシを入れます フィルターは

  • to the polarization pattern of the sky.

    空の偏光パターンの向きと 直角に置きます

  • The beetle comes out from underneath the filter

    フンコロガシは フィルターの下から

  • and it does a right-hand turn,

    出てきて 右に曲がります

  • because it comes back under the sky

    元々の向きのパターンの

  • that it was originally orientated to

    空の下に戻ったので

  • and then reorientates itself back

    元々の方角へと

  • to the direction it was originally going in.

    体の向きを変えたのです

  • So obviously beetles can see polarized light.

    彼らには光の偏光が わかるのです

  • Okay, so what we've got so far is,

    ここまでのおさらいをすると

  • what are beetles doing? They're rolling balls.

    フンコロガシはボールを転がします

  • How are they doing it? Well, they're rolling them in a straight line.

    しかも直線で転がします

  • How are they maintaining it in a particular straight line?

    何故曲がらずに 移動できるのか?

  • Well, they're looking at celestial cues in the sky,

    それは私達の目には見えない

  • some of which you and I can't see.

    天空の手掛かりを 使っているからです

  • But how do they pick up those celestial cues?

    ではその手掛かりは どう感知するのか?

  • That was what was of interest to us next.

    それがまさに次の疑問でした

  • And it was this particular little behavior, the dance,

    そしてこの踊りこそが 重要なのではないかと

  • that we thought was important, because look,

    考えたのです 何故なら

  • it takes a pause every now and then,

    このように時々休憩しています

  • and then heads off in the direction that it wants to go in.

    そして再び行きたい方角へと 向かいます

  • So what are they doing when they do this dance?

    この踊りが持つ意味は何なのか?

  • How far can we push them before they will reorientate themselves?

    何が起こると彼らは向きを 変えるのでしょう?

  • And in this experiment here, what we did was we forced them

    こちらの実験では まず無理矢理彼を

  • into a channel, and you can see he wasn't

    この溝に誘導します 良く見ると特に

  • particularly forced into this particular channel,

    無理強いはされていませんね

  • and we gradually displaced the beetle by 180 degrees

    そして徐々に 180度ずらしていき

  • until this individual ends up going in exactly the opposite direction

    最終的に元の方向とは

  • that it wanted to go in, in the first place.

    逆方向へと向かわせます

  • And let's see what his reaction is

    彼の反応を見てみましょう

  • as he's headed through 90 degrees here,

    90度の場所を通り過ぎ

  • and now he's going to -- when he ends up down here,

    歩き続け 最終的には

  • he's going to be 180 degrees in the wrong direction.

    元の方向とは 180度反対方向を向きます

  • And see what his response is.

    彼の反応を見てみると

  • He does a little dance, he turns around,

    少し踊って 回転して

  • and heads back in this. He knows exactly where he's going.

    再び溝の中を進みます

  • He knows exactly what the problem is,

    彼は何が問題なのか理解し

  • and he knows exactly how to deal with it,

    かつ対処法も心得ているのです

  • and the dance is this transition behavior

    そしてこの踊りを転機に

  • that allows them to reorientate themselves.

    彼らは正しい方向に 向き直るのです

  • So that's the dance, but after spending many years

    以上が踊りについてです しかし灼熱のアフリカで

  • sitting in the African bush watching dung beetles on nice hot days,

    何年もフンコロガシを 観察しているうちに

  • we noticed that there was another behavior

    踊りに関連するもう一つの

  • associated with the dance behavior.

    ある行動に気がついたのです

  • Every now and then, when they climb on top of the ball,

    ボールに登ると彼らは時たま

  • they wipe their face.

    顔を拭くのです

  • And you see him do it again.

    またやりましたね

  • Now we thought, now what could be going on here?

    これは一体どういうことなのでしょう?

  • Clearly the ground is very hot, and when the ground is hot,

    明らかに地面は熱いです 地面が熱いと

  • they dance more often, and when they do this particular dance,

    踊る回数が増えます そして踊ると

  • they wipe the bottom of their face.

    顔の下の方を拭くのです

  • And we thought that it could be a thermoregulatory behavior.

    これは温度調節をしているのではないか

  • We thought that maybe what they're doing is trying to

    熱い砂を払い 顔に唾をかけて

  • get off the hot soil and also spitting onto their face

    頭を冷やしているのではないかと

  • to cool their head down.

    私達は考えたのです

  • So what we did was design a couple of arenas.

    そこで二つの舞台を作りました

  • one was hot, one was cold.

    一つは熱く 一つは涼しい状態です

  • We shaded this one. We left that one hot.

    こちらは日陰に もう一つは日向に置きました

  • And then what we did was we filmed them with a thermal camera.

    そして熱探知カメラで 撮影しました

  • So what you're looking at here is a heat image

    今映っているのは 熱を映像化したものです

  • of the system, and what you can see here emerging

    そしてフンの中から低温の

  • from the poo is a cool dung ball.

    フンコロガシが出てきました

  • So the truth is, if you look at the temperature over here,

    フンコロガシは低温 つまりクール

  • dung is cool. (Laughter)

    かっこいい奴なのです(笑)

  • So all we're interested in here is comparing the temperature

    私達の関心はフンコロガシと

  • of the beetle against the background.

    周囲との温度差です

  • So the background here is around about 50 degrees centigrade.

    周囲はおよそ50℃です

  • The beetle itself and the ball are probably around about

    フンコロガシとボールはおよそ

  • 30 to 35 degrees centigrade,

    30℃から35℃くらいでしょう

  • so this is a great big ball of ice cream

    例えるなら 大きな アイスクリームの塊を

  • that this beetle is now transporting across the hot veld.

    熱い草原の上を転がしていく ようなものです

  • It isn't climbing. It isn't dancing, because

    まだ登っていません 踊っていません

  • its body temperature is actually relatively low.

    体温が比較的低いからです

  • It's about the same as yours and mine.

    私達の体温とほぼ同じです

  • And what's of interest here is that little brain is quite cool.

    そして小さな脳みそも かなり低温です

  • But if we contrast now what happens in a hot environment,

    ところが周りが熱くなると

  • look at the temperature of the soil.

    地面の温度を見てください

  • It's up around 55 to 60 degrees centigrade.

    55℃から60℃です

  • Watch how often the beetle dances.

    頻繁に踊り始めましたね

  • And look at its front legs. They're roaringly hot.

    前足を見てください 相当熱そうです

  • So the ball leaves a little thermal shadow,

    ボールは熱の影を残しています

  • and the beetle climbs on top of the ball

    そしてフンコロガシは ボールに登ります

  • and wipes its face, and all the time it's trying to cool itself down,

    顔を拭き 常に体温を下げ 熱い砂を

  • we think, and avoid the hot sand that it's walking across.

    避けようとしていると考えられます

  • And what we did then was put little boots on these legs,

    そこで靴を履かせてみました

  • because this was a way to test if the legs

    地面の温度を足で知覚するのか

  • were involved in sensing the temperature of the soil.

    確認するためです

  • And if you look over here, with boots they climb onto the ball

    ここを見て下さい 靴を履くとボールに登る

  • far less often when they had no boots on.

    回数が格段に少なくなります

  • So we described these as cool boots.

    クールブーツと命名しました

  • It was a dental compound that we used to make these boots.

    靴は歯科治療用の 材料で作りました

  • And we also cooled down the dung ball, so we were able

    またフンのボールも冷やしました

  • to put the ball in the fridge, gave them a nice cool dung ball,

    冷蔵庫で冷やしたフンを与えたのです

  • and they climbed onto that ball far less often

    するとボールが熱い時と比べて

  • than when they had a hot ball.

    登る回数がかなり減りました

  • So this is called stilting. It's a thermal behavior

    「高床歩き」です 人間も熱い砂浜を

  • that you and I do if we cross the beach,

    歩くときにします

  • we jump onto a towel, somebody has this towel --

    他人のタオルに飛び乗り

  • "Sorry, I've jumped onto your towel." --

    「失礼 踏んでしまいました」 と言って

  • and then you scuttle across onto somebody else's towel,

    別の人のタオルに 飛び移る

  • and that way you don't burn your feet.

    足を火傷せずに済みます

  • And that's exactly what the beetles are doing here.

    フンコロガシの行為も全く同じことです

  • However, there's one more story I'd like to share with you,

    もう一つお話をしたいと思います

  • and that's this particular species.

    それはこの種についてです

  • It's from a genus called Pachysoma.

    パキソーマ亜属と呼ばれ

  • There are 13 species in the genus, and they have

    13種が存在します 彼らには

  • a particular behavior that I think you will find interesting.

    興味深い習性があります

  • This is a dung beetle. Watch what he's doing.

    これはフンコロガシです 見てください

  • Can you spot the difference?

    違いが分かりますか?

  • They don't normally go this slowly. It's in slow motion.

    この映像は通常の 速度ではありませんが