生物的所有互动方式中 Of all the ways that species interact on this planet, maybe
也许最让我们最着迷的就是捕食 为什么不呢? the one that fascinates us the most is predation, and why not?
很难不被阿拉斯加棕熊迷住, It's hard not to be captivated by say, an Alaskan brown bear,
它是北美的顶级食肉动物, one of North America's apex predators, even though they get
虽然他们大部分的营养都来自坚果 虫子和浆果 much of their nutrition from nuts, bugs and berries.
你也可以说这家伙对弄碎其他动物的骨头这事 You can also tell that it's a pretty big fan of crushing
相当有兴致 因为这里有个惊人的矢状嵴 the bones of other animals because of this amazing
连接着下巴的肌肉. pronounced sagittal crest where it's jaw muscles connect.
也许我们都很着迷捕食的部分原因是 Maybe part of why we're so fascinated by predation is because
我们人类几乎都不捕食了 至少现在是这样. we are, in many ways, the planet' stop predator. At least for now.
这就是为啥我背后这些家伙会来这里. That's how most of these guys got here.
但千百年来, 我们也被其他动物捕食, But for hundreds of thousands of years, we were preyed upon as well,
不仅是熊和狼, 还有病毒, 细菌和寄生虫. not just by bears and wolves but by viruses, bacteria and parasites.
因为"捕食"不只意味着动物吃动物 Because predation isn't just animal-eats-animal.
麝牛或大角羊, 也被认为是捕食者, This muskox or this bighorn sheep can also be considered predators,
尽管他们只吃植物. even though they only eat plants.
对于了解捕食行为来说 也许最重要的是要知道 But perhaps what's most important to understand about predation
狩猎与被狩猎所导致的进化压力 is the evolutionary pressures that come with hunting
已经持续了千百年. and being hunted for thousands of years.
因为这些压力, 捕食驱动了 Because of these pressures, predation has driven all sorts
我们身边这些惊人的适应性变化, of truly amazing adaptations that we see all around us,
从有大爪子大牙齿的灰熊, from the grizzly's enormous claws and teeth,
到有群体猎食习惯的狼, to the wolf's habit of hunting in packs,
当然也有一些防守性变化, 比如叉角羚的跑步速度, as well as defensive adaptations like the speed of the pronghorn,
它是北美洲跑得最快的动物. the fastest animal in North America.
最终, 捕食者和猎物之间的相互影响 In the end, the effect of predator-prey interaction
变成了进化的军备竞赛, is an evolutionary arms race that results in the mind-boggling
导致每个生态系统里都有巨大的生物多样性, amount of diversity we see in any ecosystem,
从北落基山脉, 一路到非洲大草原. from the Northern Rockies, all the way to the African savanna.
这种进化军备竞赛被称为 共同演化 This arms race is known as co-evolution, the process by which
两个物种间相互影响 the interactions between two species affect
导致双方都进化了. the evolutionary development of both.
共同进化这事自寒武纪大爆发就有了, It's been going on since the Cambrian explosion more than half
这事发生在5亿多年前, 从那时起就一直在出现新的生物, a billion years ago, and it will continue spawning new bursts of
也许很久以后 我们人类会自相残杀直到灭绝. diversity long after we humans have eaten ourselves into extinction.
也许, 我们最后也会呆在这样的地方. And, maybe, we'll end up in a place like this.
我们倾向于认为"捕食"只指动物, We tend to think of predation in terms of animals,
狮子吃斑马, 狼吃羊, 鹰吃老鼠. lions hunting zebras, wolves killing sheep, hawks eating mice.
但实际上 "捕食"不仅意味着食肉动物做的那些事. But predation is much more than carnivores doing their thing.
它适用于任何生物之间的相互作用 It applies to any number of interactions where
只要是一种动物为了能量杀掉另一种动物就算. one type of organism kills another for its energy.
知道这个很重要, 因为很多生态问题 That's an important thing to note, because of a lot of ecology
说到底就是能量如何流过自然. comes down to the flow of energy through nature.
所有生物都需要能量来生存, And every living thing needs energy to meet its twin
以满足2个进化目标 继续活着 以及 繁育很多后代. evolutionary goals of staying alive and making lots of babies.
捕食者杀其他动物是因为它饿了 So predators kill because they're hungry, but they're hungry
它饿了是因为它需要能量来生存和繁殖 because they need energyto survive and reproduce.
对被捕食者来说, 很明显这种相互作用的风险是很高的 For prey, these interactions are especially high-stakes obviously,
一不留神 because nothing quite quashes
繁殖机会就变0了 your reproductive chances like being dead.
但是地球上的几乎所有能量, 都是从植物开始的. But almost all energy on earth starts with plants.
想想吃草的野牛. So consider bison eating grass.
这类捕食者叫做"食草动物" That's a type of predation called herbivory where an organism
它们吃植物或藻类来获取能量. eats plants or algae to capture their energy.
这个在你眼里可能算不上是捕食, It may not really seem like predation to you,
但野牛吃草, 海牛吃海带, but bison eating grass, manatees eating seaweed,
海胆吃水藻, 都是生物通过吃其他生物 and sea urchins munching on algae are all examples of organisms
来获取源自太阳的能量. eating other organisms to ingest the energy of the sun.
还有"寄生", 它是捕食的另一种形式, There's also parasitism, another form of predation in which
生物从宿主那里获得能量, 一般还会伤害宿主, organisms derive energy from a host, usually harming it,
或害死宿主.. and sometimes killing it in the process.
拿线形虫举例, 蝗虫如果不小心吃掉了它们 Hairworms, for example, devour the insides of grasshoppers
它会给蝗虫洗脑 然后控制蝗虫去做自杀性跳水. and then brainwash them to make suicidal leaps into water.
这种水生虫子究竟是怎么进入蝗虫体内的. How exactly, the water-borne worm finds its way into a grasshopper
现在还是个谜. 蚊子携带线形虫的幼虫是一种可能的途径. is a mystery, though larvae carried by mosquitoes is a likely route.
一旦进到蝗虫体里, 线形虫会吃掉所有 Once inside the grasshopper, the worm eats everything
对宿主来说非必要的东西. 它还会生长到宿主身长的好几倍. non-essential to its host as it grows several times
对宿主来说非必要的东西. 它还会生长到宿主身长的好几倍. the length of its host's body.
当蝗虫只剩脑袋和脚时 When only the grasshopper's head and legs remain,
线形虫就准备繁殖了. the hairworm is ready to reproduce.
它会控制蝗虫. And that's when the brainwashing begins.
线形虫是在水中繁殖的, 但蝗虫不能游泳. See, hairworms breed in water, but grasshoppers can't swim.
线形虫往宿主体里撒播化学物质, So hairworms pump their hosts full of chemicals that prompt an
叫它跳到水里. inescapable urge to leap into a body of water.
一旦蝗虫跳进水里, 线形虫就自由了 Once the grasshopper makes the leap, the hairworm is free
它会去找个伴侣. 恶心啊. to burrow out of the host and find a mate. Ew.
追逐和吃掉瞪羚是一回事. Yeah, chasing and eating a gazelle is one thing.
但把猎物变成一个自杀僵尸? But turning your prey into, like, a suicidal zombie?
这, 我的朋友, 也算捕食. That, my friends, is predation.
很明显, 捕食者和被捕食者数百万年来 So, clearly, predator and prey both have millions of years
都有自己的方法生存 of tricks up their sleeves, or stored in their DNA,
因为大家最终 because everyone is ultimately playing by the same set
遵守的都是进化法则. of evolutionary rules.
无论狮子或斑马, 蚂蚱或线形虫 , Whether lion or zebra, grasshopper or hairworm,
野牛或是青草. 获得能量并且不被吃掉 or bison or grass, gaining energy while not being eaten
是繁殖成功的前提条件. is a prerequisite to reproductive success.
所以 为了生存 捕食者和被捕食者 So, the need to survive constantly forces predator and prey to adapt
都在这个无休止的军备竞赛中 进化出了武器或防守手段. weapons and defense in an ever-ending evolutionary arms race.
在捕食者这边, 狩猎和觅食的手段 On the predator side, hunting and feeding adaptations
我们都很熟悉了: are obvious and familiar:
狼的敏锐嗅觉 和 剔肉的牙齿, a wolf's keen sense of smell and flesh-ripping teeth
老鹰雪亮的眼睛 and an eagle's sharp eyes
和抓猎物的利爪. and prey-gripping talons.
其他生物, 比如响尾蛇, 用热感应器官 Other creatures, like rattlesnakes, use heat-sensing organs
来找小型啮齿动物, 然后用毒液弄死它们. to seek out small rodents, and toxic venom to strike them dead.
但协同进化使得被捕食者 But this is where co-evolution takes the stage to give the prey
也进化了. a stake in the evolutionary arms race, too.
因为被别人抓住对传播基因来说是件很可怕的事 Since being caught by a predator is kind of terrible for anything
所以动物进化出了各种东西来避免被干掉 that hopes to spread its genes, species have adapted all sorts
所以动物进化出了各种东西来避免被干掉 of ways to avoid getting killed.
躲避捕食者的行为 These can be broken up by what kinds of predatory behavior
可以分成以下几类: these adaptions are designed
避免被找到, 避免被捉到, 避免被干掉. to avoid, namely: detection, capture, and handling.
为了避免被找到, 某些被捕食者进化出了伪装, To avoid detection, some prey adapt cryptic coloration,
以帮助动物融入背景. which we better know as camouflage, to help a species
以帮助动物融入背景. blend into the background.
竹节虫 看起来像树枝, Stick insects that have adapted to look like sticks,
卷叶虫 看起来像叶子, leaf insects that look like leaves,
白靴兔, 它们冬天是白色的, 可以融入白雪背景 snowshoe hares that turn white in the winter to blend in with the snow
夏天会变成棕色, 以融入草堆, 这些都是很好的例子. and brown in the summer to blend in with the grasses are all good examples.
避免被抓住有时非常简单: Avoiding capture is at times pretty straightforward:
例如, 羚羊, 它能跑得非常非常快来躲避掠食者. antelope, for example, flee predators with great, leaping speed.
其他的则聚成一团, 比如野牛 Others find safety in numbers, such as bison forming giant herds
或鲱鱼. or herring grouping in schools.
它们扎堆并不会使得自己不被找到 This kind of grouping certainly doesn't protect the prey
但它极大地减少了 from being detected, but it greatly reduces chances that
被捕食者挑中的几率, any individual will get picked off by a predator,
特别是被包在中间的那些家伙. especially fit members of the group in the middle of the pack.
最后一种适应性变化是最酷, 也是我们最熟悉的. And finally, some of the coolest and most familiar adaptations
避免被干掉. are those that prevent handling.
植物在这事儿上是专家: 想想玫瑰的刺 Plants are experts at these: Think of a rose's thorns
或抓昆虫的树液陷阱, or tree sap that traps insects,
或是非洲金合欢树的尖刺. or the branches of an African acacia tree.
长颈鹿很讨厌它们, They're most thorny within the range of tree-munching giraffes, but
但树上高一点的地方, 就没有那么多刺. above where their long necks can reach, there aren't as many thorns.
其他植物也会用化学武器, Other plants also produce chemical weapons,
比如烟草植物会产生尼古丁 such as a tobacco plant nicotine and the tannins produced
还有许多植物会产生单宁酸 比如葡萄 by many plants, like grapevines, to fend off foragers.
但当你看到动物 But things get really weird when you see what animals do
用化学招数时 事情确实变得很奇怪 with this bag of chemical tricks.
因为这些小动物往往不仅有邪恶又有毒的混合物保护自己, Because often these critters not only have wicked, toxic cocktails
还有不少演变出了"警戒色" to defend themselves, many also have evolved aposematic,
或者说"警告色" or warning coloration.
它们用明亮的对比色, 比如身上有黄色和黑色火蝾螈. The bright, contrasting colors, such as yellow and black
以及身上有红色 黄色和黑色的银环蛇. splotches of the fire salamander for the red, yellow, and black
它们清楚的告诉天敌 bands of coral snakes make it clear to predators
吃掉它们会是个严重的错误 that eating them would be a serious mistake.
当你回想时, 大自然里到处都是那些 And when you think of it, nature is full of species that
带黑色和黄色, 或是红色和黑色的动物. are black and yellow in color, or red and black.
我们倾向于不惜一切代价躲开它们. We tend to avoid them at all costs.
我们很聪明, 大多数其他食肉动物也是. We're smart that way. And so are most other predators.
这当然不是巧合. This, of course, is no coincidence.
正如德国博物学家 弗里茨 · 米勒 在1870年说的, As German naturalist Fritz Muller noted in the 1870s,
那些难吃的品种, 比如布谷鸟蜜蜂, 黄夹克黄蜂, unpalatable species, such as a cuckoo bees, yellow jackets,
实际上几乎每一种蜜蜂和黄蜂 , actually almost every kind of bee and wasp,
彼此都很相似, 它们都有相似的颜色和图案. resemble each other, using similar colors and patterns.
他发现 那些难吃的猎物会用相同的颜色图案互相模仿 He figured out that the more unpalatable prey there are that use
互相模仿的物种越多 捕食者就越要避免 the same color patterns, the more likely predators are to avoid
那些看起来几乎一样的猎物. all prey with that appearance in general.
这种防御手段叫做 米氏拟态. This defense technique is known today as Mullerian mimicry.
但意料之中的是 那些看起来很危险的动物 But, it turns out, unsurprisingly, some critters that look
笑到了最后 dangerous are getting the last laugh.
即使它们对捕食者来说其实是很美味的 Because many of them would actually be quite tasty to any predator.
但它们欺骗了所有人 They just trick everyone by copying the looks
让别人以为它是危险的家伙. of the truly dangerous species.
这叫做 贝茨拟态, This technique called is Batesian mimicry,
为了解释给你听, 我得找个凳子坐下来 and to explain it to you, I'm going to need to sit down.
我给你一次机会 I'll give you one guess to figure out
猜猜看谁是"贝茨拟态"的命名者. who first described Batesian mimicry.
没错, 就是贝茨. That's right, it was Bates.
更具体地说, 是亨利 · 沃尔特 · 贝茨 More specifically, it was Henry Walter Bates,
他是19世纪的 英国博物学家和探险家. a 19th century British Naturalist and explorer.
贝茨出生于1825年 他家是中产阶级家庭 Bates was born in 1825 to a middle-class family that
以制作针织品为生. paid the bills by making hosiery.
他把大部分时间花在阅读有关昆虫的书, He spent most of his spare time reading, often about bugs,
他在18岁的时候 在《动物学家》杂志上发了一篇关于甲虫的文章 and by the young age of 18 he was a budding entomologist
成了一个崭露头角的昆虫学家 with a publication on beetles already to his credit.
几年之后 他遇到了 It was a few years later that he met
著名的昆虫学家 阿尔弗雷德 · 拉塞尔 · 华莱士 the famed entomologist Alfred Russel Wallace.
两人一拍即合, 在1847年, 华莱士建议走一趟南美洲 The two hit it off and Wallace, in 1847, proposed they take a trip
收集昆虫. to South America to collect insects.
他们的计划是 把收集到的标本送回英国 They would finance their travels by sending collected specimens
卖给博物馆和私人收藏家 把收入用作旅行的资金来源. back to England for sale to museums and private collectors.
他们在第二年就起航出发了 The pair set sail the following year, and after four years
在4年之后 华莱士不玩了 干别的去了, in the field, Wallace moved on, but Bates, apparently not wanting
但贝茨不想回家做针织品生意, 于是他留了下来 to get into the hosiery business, stayed behind, spending
接下来的11年里他都在丛林里晃悠 the next 11 years in the jungle.
他收集了近 15000 种昆虫 All tolled, he collected nearly 15,000 species,
其中大概 8000 种是新物种. about 8,000 of them new to science.
1859年 贝茨回家了 在短短几个月后 Just a few months after Bates arrived home in 1859 ,
达尔文发表了他的《物种起源》 Darwin published his On the Origin of Species.
贝茨读了他的书, 并且他觉得他能提供证据来支持 Bates read it and figured he could contribute evidence to support
自然选择理论, 也就是他的昆虫标本. the new theory of natural selection from his insect collection.
两年后 他发布了一篇论文 Two years later he presented a paper that showed
关于不同品种的蝴蝶是怎么进化出 how different species of butterfly developed
几乎相同的翅膀颜色和图案. nearly identical color patterns on their wings.
例如, 有一种叫"釉蛱蝶"的蝴蝶 For example, butterflies called Heliconiinae, which were
它移动的很慢, 数量也很多, 但它们有毒, slow-moving and abundant, but toxic, were nearly
它们几乎和粉蝶看起来一模一样, 粉蝶的数量少一些 但是没毒. identical to Pieridae, which were more rare but harmless.
贝茨认为, 自然选择 Bates concluded that natural selection had driven the
驱动没毒的蝴蝶模仿有毒的蝴蝶 harmless butterflies to mimic the patterns on the harmful
让鸟不吃它们 butterflies for their individual birds to survive predation by birds.
这一发现帮助了贝茨的职业生涯和声誉, The discovery helped launch Bates' career and reputation,
他后来写了一本书, 讲述他的冒险故事和新发现 and he went on to recount his adventures and other discoveries
《在亚马逊河的博物学家》 in a book, The Naturalist on the River Amazon, and later took
再后来, 他跑去了皇家地理学会当秘书 a job as secretary to the Royal Geographic Society.
虽然贝茨在 1892 年去世了 但贝茨拟态的概念 Though Bates died in 1892 , the concept of Batesian mimicry
还继续着吸引今天的科学家 continues to fascinate scientists today.
例如 为什么它们模仿更危险的同类时 Why, for example, are so many mimics not perfect imitations
几乎全都模仿的不完美? of their more dangerous counterparts?
是因为完美的模仿没必要吗? Is it because perfect imitation isn't necessary to do the job?
还是说它们缺少的必要基因 Or because mimics lack the genes necessary to
来完美模仿吗? perfectly resemble their poisonous counterparts?
也许21世纪的昆虫学家 Perhaps budding entomologists armed with 21st century
能解决这些问题 tools will finally unlock the answers.
不要以为只有被捕食者会模仿 But don't think that prey are the only crafty mimics out there.
在这场军备竞赛里 有些捕食者也学会了模仿 In the arms race, some predators have learned how to win
来获得食物 food through imitation as well.
我们已经讨论过了鳄龟的舌头 You've heard me talk about snapping turtles with tongues
通过模仿虫子来引诱鱼 that resemble wiggling worms to lure fish.
不要让我唠叨琵琶鱼! And don't get me started about anglerfish!
如果"捕食"有教会我们东西 那就是没什么可以天长地久 If predation teaches us anything, it's that nothing lasts forever.
不只是对被捕食者来说 对每个生物都一样 Not just for prey, but for every living thing,
因为捕食者和被捕食者之间的相互作用 because the interaction between predator
驱动了进化. and prey keeps driving evolutionary change.
但生态群落本身 But the communities themselves that we've been talking about for
当然也会发生变化. the last two weeks don't stay the same, either, of course.
总是有新租户迁入栖息地, New tenants are always moving into a habitat, and every now
也总会有新房东接管这里. and again a new landlord takes over.
这一切使得这个世界充满活力 美丽和令人兴奋 That's part of what makes the living world such a dynamic, beautiful
这也是我们下周要讨论的"生态演替". and exciting place, and it's what we'll be exploring next week.
感谢收看本集生态学速成班 Thank you for watching this episode of Crash Course Ecology.
如果你想复习什么 If you want to review anything,
那边有张表 there's a table of contents over there.
感谢所有帮助制作节目的人 Thanks to everyone who helped put
感谢所有帮助制作节目的人 this episode of Crash Course together.
如果你有任何问题 意见或想法 And if you have any questions, comments or ideas you can
可以去 Facebook 或 Twitter 找我们 当然 leave them for us on Facebook or Twitter, or of course,
也可以在下面留言. down in the comments below.
我们下次再见. We'll see you next time.