And in particular, how the simple parts of organizations

組織がいかに作用するのかを見るのが好きなので アリの研究をしています

interact to create the behavior of the whole organization.

いかにして 単純な部分同士の相互作用から

So, ant colonies are a good example of an organization like that,

全体の習性が生じるのか見るのが好きです

and there are many others. The web is one.

ですからアリコロニーはそのような組織の良い例なのです

There are many biological systems like that --

インターネットもその一例だと言えますし

brains, cells, developing embryos.

脳 細胞 発達中の受精卵のような

There are about 10,000 species of ants.

生物学的システムもたくさんあります

They all live in colonies consisting of one or a few queens,

アリは約一万種います

and then all the ants you see walking around are sterile female workers.

どのアリも女王アリ1匹もしくは数匹がいるアリコロニーに住んでいて

And all ant colonies have in common that there's no central control.

外で見かけるアリはどれも産卵しない雌アリです

Nobody tells anybody what to do.

どのアリコロニーにも共通するのは中央制御が存在せず

The queen just lays the eggs. There's no management.

指揮監督がいません

No ant directs the behavior of any other ant.

女王アリが産卵するだけで 管理者はいません

And I try to figure out how that works.

アリの行動を監督するアリはいなのです

And I've been working for the past 20 years

私はその仕組みを解明しようとしています

on a population of seed-eating ants in southeastern Arizona.

過去20年間 アリゾナ州南東に生息する―

Here's my study site. This is really a picture of ants,

種を食べるアリの個体群を研究しています

and the rabbit just happens to be there.

これが研究場所で アリの写真ですが

And these ants are called harvester ants because they eat seeds.

たまたまウサギが写っています

This is the nest of the mature colony, and there's the nest entrance.

このアリが収穫アリと呼ばれるのは種を食べるからです

And they forage maybe for about 20 meters away,

これは成長したコロニーの巣と巣の入口です

gather up the seeds and bring them back to the nest, and store them.

アリは20mほど先まで食糧を探しに行き

And every year I go there and make a map of my study site.

種を集めて巣に持ち帰り 貯えます

This is just a road. And it's not very big:

私は毎年ここに行き 研究場所の地図を作成しています

it's about 250 meters on one side, 400 on the other.

これはただの道路で 広さは

And every colony has a name, which is a number,

だいたい縦250m 横400mです

which is painted on a rock. And I go there every year

どのコロニーにも識別番号をつけ

and look for all the colonies that were alive the year before,

石に書いておきます

and figure out which ones have died, and put all the new ones on the map.

毎年 死んだコロニーを調べ

And by doing this I know how old they all are.

新しく出来た巣は地図に追加します

And because of that, I've been able to study how their behavior changes

こうすることでコロニーの年数を把握します

as the colony gets older and larger.

その結果 コロニーの成長につれて

So I want to tell you about the life cycle of a colony.

彼らの行動の変化を研究することが出来るのです

Ants never make more ants; colonies make more colonies.

コロニーのライフサイクルを説明します

And they do that by each year sending out the reproductives --

着目すべきは個々のアリではなく 組織として働くコロニーです

those are the ones with wings -- on a mating flight.

毎年 羽のある繁殖アリを交尾飛行へと

So every year, on the same day -- and it's a mystery exactly how that happens --

送りだすことで繁殖させます

each colony sends out its virgin, unmated queens with wings, and the males,

いかに起きるかは謎ですが毎年同じ日に

and they all fly to a common place. And they mate.

どのコロニーも羽のある処女女王アリと雄アリを送りだし

And this shows a recently virgin queen. Here's her wings.

みんな決まった場所へ飛んで行き 交尾をします

And she's in the process of mating with this male,

これは最近の羽のついた処女女王アリです

and there's another male on top waiting his turn.

女王アリは雄アリと交尾中で

Often the queens mate more than once.

別の雄アリが2匹の上で順番を待っています

And after that, the males all die. That's it for them.

女王アリはたいてい2回以上交尾をして

(Laughter)

交尾後 雄アリは全て死にます　ご苦労さま

And then the newly mated queens fly off somewhere, drop their wings,

（笑）

dig a hole and go into that hole and start laying eggs.

交尾をした女王アリは別の場所へと飛び 羽を落とし

And they will live for 15 or 20 years, continuing to lay eggs

穴を掘って中へ入り 産卵し始めます

using the sperm from that original mating.

女王アリは交尾の際に蓄えた精子を使って産卵し続け

So the queen goes down in there.

約15~20年生きます

She lays eggs, she feeds the larvae -- so an ant starts as an egg, then it's a larva.

女王アリは地中に入り

She feeds the larvae by regurgitating from her fat reserves.

卵を産んで それが幼虫になると 女王アリは蓄えてある―

Then, as soon as the ants -- the first group of ants -- emerge,

脂肪を吐き出して幼虫を育てます

they're larvae. Then they're pupae. Then they come out as adult ants.

そして第一番目のアリ集団が発生するや否や

They go out, they get the food, they dig the nest,

幼虫 さなぎを経てアリの成虫になります

and the queen never comes out again.

アリは地上へ上がり 食べ物を得て 巣を掘り

So this is a one-year-old colony -- this happens to be 536.

女王は2度と地上に上がりません

There's the nest entrance, there's a pencil for scale.

これは出来てから1年経つコロニー536番です

So this is the colony founded by a queen the previous summer.

巣の入口の大きさ比較に鉛筆を置いてあります

This is a three-year-old colony.

これは昨夏出来たばかりのコロニーです

There's the nest entrance, there's a pencil for scale.

これは3年目のコロニーです

They make a midden, a pile of refuse -- mostly the husks of the seeds that they eat.

巣の入口の大きさ比較に鉛筆を置いてあります

This is a five-year-old colony. This is the nest entrance, here's a pencil for scale.

アリが作るゴミの山は大方が食糧の種の皮です

This is about as big as they get, about a meter across.

これは5年目のコロニーで 巣の入口の大きさ比較に鉛筆を置いてあります

And then this is how colony size and numbers of worker ants changes --

巣は大きくても直径1m程度です

so this is about 10,000 worker ants --

このグラフはコロニーの大きさを表す働きアリの数が

changes as a function of colony age, in years.

コロニーの年数とともにどう変化するかを示します

So it starts out with zero ants, just the founding queen,

これは働きアリ約1万匹です

and it grows to a size of about 10 or 12 thousand ants when the colony is five.

最初は女王アリだけで 働きアリ０匹から始まり

And it stays that size until the queen dies

5年経つまでに1万～1万2千匹ほどまで増加します

and there's nobody to make more ants, when she's about 15 or 20 years old.

その後 15～20歳になった女王アリが

And it's when they reach this stable size, in numbers of ants,

死んでアリが生まれなくなるまで アリの数は変化しません

that they start to reproduce.

アリの数がここまで安定すると

That is, to send more winged queens and males to that year's mating flight.

アリは繁殖し始めます

And I know how colony size changes as a function of colony age

羽のある女王アリと雄アリをその年の交尾飛行へと送りだすのです

because I've dug up colonies of known age and counted all the ants. (Laughter)

コロニーの使用年数と大きさの相関関係を把握しているのは

So that's not the most fun part of this research, although it's interesting.

使用年数が確実なコロニーを掘り起こし すべてのアリを数えたからです

(Laughter)

興味深いんですが この研究で一番楽しい部分とは言えません

Really the question that I think about with these ants is what I call task allocation.

（笑）

That's not just how is the colony organized,

私が知りたいのは このアリの仕事の割当てです

but how does it change what it's doing?

コロニーの組織のされ方ではなく

How is it that the colony manages to adjust

いかに動きが変わるのか？

the numbers of workers performing each task as conditions change?

状況の変化と共に 各仕事につく働きアリの数を

So, things happen to an ant colony.

いかにコロニーは調整しているのか？

When it rains in the summer, it floods in the desert.

色々なことが考えられます

There's a lot of damage to the nest,

夏の雨で砂漠が氾濫すれば

and extra ants are needed to clean up that mess.

巣には大きな被害が出て

When extra food becomes available --

後片付けをするアリが余分に必要となります

and this is what everybody knows about picnics --

たくさん食糧が調達できる時は

then extra ants are allocated to collect the food.

ピクニックでよく見かけるように

So, with nobody telling anybody what to do, how is it that

食糧収集にいつも以上のアリが配置されます

the colony manages to adjust the numbers of workers performing each task?

指揮監督なしで いかにコロニーでは

And that's the process that I call task allocation.

各仕事に就くアリの数を調整するのでしょう？

And in harvester ants, I divide the tasks

これは私が仕事分配と呼んでいる過程です

of the ants I see just outside the nest

巣の外で見かける

into these four categories: where an ant is foraging,

アリの仕事を

when it's out along the foraging trail, searching for food or bringing food back.

４種に分類しました

The patrollers -- that's supposed to be a magnifying glass --

外で食糧を調達してくる食糧アリ

are an interesting group that go out early in the morning

虫メガネを持っている偵察アリは

before the foragers are active.

食糧アリの活動前に

They somehow choose the direction that the foragers will go,

早朝から動きだす面白い集団です

and by coming back -- just by making it back --

どういうわけか 偵察アリは食糧アリが行く方向を決め

they tell the foragers that it's safe to go out.

その方向から無事に帰ってくることで

Then the nest maintenance workers work inside the nest,

外出しても安全だと食糧アリに教えます

and I wanted to say that the nests look a lot like Bill Lishman's house.

整備アリは巣の中で働きます

That is, that there are chambers inside,

巣はビル リシュマンの家にそっくりです

they line the walls of the chambers with moist soil

と言うのも 中に小室があって

and it dries to a kind of an adobe-like surface in it.

湿った土で小室の壁を覆うと

It also looks very similar to some of the cave dwellings

日干し煉瓦のように乾きます

of the Hopi people that are in that area.

この地域に見られるホピ族の

And the nest maintenance workers do that inside the nest,

洞窟住居にも類似しています

and then they come out of the nest carrying bits of dry soil in their mandibles.

整備アリは巣の中をそのように施し

So you see the nest maintenance workers come out with a bit of sand,

大あごで乾いた土を地上に運びます

put it down, turn around, and go back in.

砂を持って出てくる整備アリは

And finally, the midden workers put some kind of territorial chemical in the garbage.

砂を置き 方向転換して 戻ります

So what you see the midden workers doing is making a pile of refuse.

最後に ごみアリは ある縄張り物質をゴミにつけます

On one day, it'll all be here, and then the next day

ごみアリはゴミの山を作るんです

they'll move it over there, and then they'll move it back.

その日によって違った場所に

So that's what the midden workers do.

ゴミの山を作りだします

And these four groups are just the ants outside the nest.

それがごみアリの仕事です

So that's only about 25 percent of the colony, and they're the oldest ants.

この4つのグループは巣の外で仕事をするアリで

So, an ant starts out somewhere near the queen.

全体のわずか25％で 最年長アリです

And when we dig up nests we find they're about as deep

どのアリも女王アリの近くから出てきたわけです

as the colony is wide, so about a meter deep for the big old nests.

掘り起こすと 巣はコロニーの幅ほどの深さがあり

And then there's another long tunnel and a chamber, where we often find the queen,

大きくて古い巣は深さが1mほどあります

after eight hours of hacking away at the rock with pickaxes.

つるはしで岩を８時間叩き割って行くと

I don't think that chamber has evolved because of me and my backhoe

長い通路の奥の小部屋に女王アリを見つけます

and my crew of students with pickaxes,

我々がショベルカーやつるはしで掘り起こした為に

but instead because when there's flooding,

小室がこの形になったとは思いません

occasionally the colony has to go down deep.

時々起こる洪水のため

So there's this whole network of chambers.

コロニーは深さがなくてはいけません

The queen's in there somewhere; she just lays eggs.

それで これほどまでの小室があるのです

There's the larvae, and they consume most of the food.

女王アリはどこかで産卵だけしています

And this is true of most ants --

幼虫は食糧のほとんどを消費します

that the ants you see walking around don't do much eating.

ほとんどのアリに共通していることですが

They bring it back and feed it to the larvae.

外で見かけるアリはあまり食べることをしません

When the foragers come in with food, they just drop it into the upper chamber,

食糧を調達し幼虫に餌付けします

and other ants come up from below, get the food,

食糧アリが食糧を持ってくると上部の小室へと投げ込みます

bring it back, husk the seeds, and pile them up.

下から別のアリがやってきて食糧を受け取り

There are nest maintenance workers working throughout the nest.

運んで種の皮をむき 積み上げます

And curiously, and interestingly, it looks as though at any time

整備アリは巣の至る所で働いています

about half the ants in the colony are just doing nothing.

面白いことに どんな時も コロニーにいるアリの約半分は

So, despite what it says in the Bible,

何もしていないかのように見えるのです

about, you know, "Look to the ant, thou sluggard,"

聖書には “怠け者よ

in fact, you could think of those ants as reserves.

アリのところに行ってみよ” とありますが

That is to say, if something happened -- and I've never seen anything like this happen,

このようなアリは補欠選手と考えてもいいでしょう

but I've only been looking for 20 years --

私の20年の研究では見たことがありませんが

if something happened, they might all come out if they were needed.

いざという時には

But in fact, mostly they're just hanging around in there.

全てのアリが出てくるかも知れません

And I think it's a very interesting question --

でも 大抵その辺でうろついているだけです

what is there about the way the colony is organized

私が興味を惹かれるのは

that might give some function to a reserve of ants who are doing nothing?

何もしていないアリの予備軍に何か役割を出しうる

And they sort of stand as a buffer in between

コロニーの組織のされ方とは何なのか？

the ants working deep inside the nest and the ants working outside.

何もしないアリは巣の奥深くで働くアリと

And if you mark ants that are working outside, and dig up a colony,

外で働くアリの調停者のような立場にいます

you never see them deep down.

外で働くアリに印をつけてコロニーを掘ると

So what's happening is that the ants work inside the nest when they're younger.

絶対に彼らを巣の奥で見かけません

They somehow get into this reserve.

と言うのもアリは若い時に巣の中で働くのです

And then eventually they get recruited to join this exterior workforce.

いつの間にか この補欠組に入り

And once they belong to the ants that work outside, they never go back down.

ついには外で働くアリとなります

Now ants -- most ants, including these, don't see very well.

一度外で働くようになると地中には戻りません

They have eyes, they can distinguish between light and dark,

大方のアリは目がよく見えません

but they mostly work by smell.

明暗を見分けられる程度の目で

So just to reinforce that what you might have thought

ほとんどを嗅覚に頼っています

about ant queens isn't true --

ですから女王アリが指揮していると思われたら

you know, even if the queen did have the intelligence

それは違います

to send chemical messages through this whole network of chambers

女王アリがアリ全体に指令を出せる―

to tell the ants outside what to do,

化学的なメッセージを送る知能を持っていたとしても

there is no way that such messages could make it in time to see

そんなメッセージで

the shifts in the allocation of workers that we actually see outside the nest.

適切なタイミングに働きアリの仕事割り当ての

So that's one way that we know the queen isn't directing the behavior of the colony.

変更を届けられることは絶対にあり得ないので

So when I first set out to work on task allocation,

女王はコロニーの動きを指揮していないと分かるのです

my first question was, "What's the relationship

仕事分配の研究を始めたとき

between the ants doing different tasks?

最初の疑問は “別の仕事をするアリ同士の

Does it matter to the foragers what the nest maintenance workers are doing?

関係はどうなっているか” でした

Does it matter to the midden workers what the patrollers are doing?"

食糧アリにとって整備アリが何をしているのか問題なのか？

And I was working in the context of a view of ant colonies in which each ant

ごみアリにとって偵察アリが何をしているのか問題なのか？

was somehow dedicated to its task from birth

生まれてからずっと自分の仕事に徹し 流れ作業における

and sort of performed independently of the others,

自分の位置は知っていても

knowing its place on the assembly line.

他のアリとは独立して作業しているという見方で

And instead I wanted to ask, "How are the different task groups interdependent?"

研究をしていました

So I did experiments where I changed one thing.

その代わりに異なるグループ間の依存関係を問う事にしました

So for example, I created more work for the nest maintenance workers

条件を一つ変えて実験をしてみました

by putting out a pile of toothpicks near the nest entrance,

例えば 整備アリが活動をし始める朝早くに

early in the morning when the nest maintenance workers are first active.

巣の入口近くに楊枝を積み上げて

This is what it looks like about 20 minutes later.

整備アリの仕事を増やしてみました

Here it is about 40 minutes later.

約20分後にはこのようになり

And the nest maintenance workers just take all the toothpicks

約40分後にはこのようになりました

to the outer edge of the nest mound and leave them there.

整備アリは楊枝を巣の端に運び

And what I wanted to know was, "OK,

そこに放置するのです

here's a situation where extra nest maintenance workers were recruited --

それで次に浮かんだ疑問は

is this going to have any effect on the workers performing other tasks?"

いつも以上の整備アリが召集された場合

Then we repeated all those experiments with the ants marked.

別の仕事をしているアリに影響は出るのか？

So here's some blue nest maintenance workers.

印をつけたアリで再度実験を行いました

And lately we've gotten more sophisticated

青く印をつけた整備アリです

and we have this three-color system.

最近は以前より凝って

And we can mark them individually so we know which ant is which.

３色使っています

We started out with model airplane paint

1匹ずつ印をつけるので個体が識別できます

and then we found these wonderful little Japanese markers,

最初はプラモデル用のペンを

and they work really well.

使いましたが その後 日本製の

And so just to summarize the result,

優れたペンを見つけました

well it turns out that yes, the different tasks are interdependent.

結果はと言うと

So, if I change the numbers performing one task,

異なる仕事は互いに関係があり

it changes the numbers performing another.