打破人们对于猪的错误认知
BBC亨利·尼科尔斯（Henry Nicholls）(2023年10月7日)
在泥里打滚的家猪（图片来源：Lynn M. Stone/NPL）
传说：猪会在排泄物中睡觉和拱来拱去。猪常常大汗淋漓。猪是不爱干净的动物。猪是粉色的。公猪的性高潮时间可长达半小时。
实际情况：人们对猪的这些成见恰恰是饲养环境糟糕的最好写照。野猪可不会在便便中睡觉或者拱来拱去的。它们是草食动物。它们会在泥浆中打滚，但仅仅是因为这是一种保持凉爽的好方法。家猪往往是粉色，但也是人类刻意影响的结果。公猪一次可射精达数分钟之久。
一只家猪（Sus scrofa）（图片来源：Nick Turner/NPL）
电影《低俗小说》（Pulp Fiction）中，塞缪尔·L·杰克逊（Samuel L. Jackson）饰演的职业杀手朱洛斯·维尼菲尔德（Jules Winnfield）在解释自己不吃猪肉的原因时说：“我不吃猪这种动物，因为猪缺乏觉悟，连自己的排泄物都不管。”
“瑞士巴塞尔动物园有一群野猪因为讲究食品卫生而出名。”
维尼菲尔德如果能花点时间想想，也许就不会对猪那么刻薄。兔子会开心地藏起自己的粪粒，让相对难以消化的草料有机会第二次通过消化系统，但却没人会对小兔的这种行为横加指责。
野猪（我们的家猪就从它们驯化而来）是一种杂食动物，对自己吃的东西不会太挑剔。但野猪的食物中，90% 都是植物，因而它们可能对便便并没有特别的兴趣。
如果家猪偶然吃上自己的便便，最有可能是因为猪圈的狭小让其勉为其难。
爱沙尼亚雪地上的野猪（Sus scrofa）（图片来源：《欧洲野生动物奇观》（Wild Wonders of Europe）/Zacek/NPL）
实际上，瑞士巴塞尔动物园有一群野猪因为讲究食品卫生而出名。
“猪猪不会在泥浆中打滚，但为了保持凉爽，它们也许会那么做。”
人们给野猪喂食表面沾上沙子的苹果片。野猪不会立即去吃，而是将苹果片拿到“穿过其围场的小溪边上，在那里将苹果片放进水中用鼻子来回拨动，然后再吃掉。”
即使真的饿极了，它们也会花时间把食物冲洗干净。但野猪对干净的苹果却从不会这么做。
除了对食物的选择，猪一般还背负着肮脏的臭名。
在泥浆里打滚的一只野猪（Sus scrofa）（图片来源：Roger Powell/NPL)
猪并不会在泥浆中打滚，但为了保持凉爽，它们也许会那么做。
这是因为，猪不具备有排汗功能的汗腺，所以，下次再有人说“像猪一样出汗（汗如雨下）”时，您可要记住这一点。这种生理现象意味着，猪面临严重的身体过热风险，泥浆比干净的水蒸发要慢得多。
英国牛津大学的格雷格·拉尔森（Greger Larson）认为：“猪与其他动物一样，也会设法让自己感到舒服，如果弄脏自己能让身体保持凉爽，它们就会义无反顾地去这样做。”
皮肤表面沾上的泥浆层还能像防晒霜一样避免皮肤晒伤，并且能充当防止蚊虫叮咬的防蚊防虫液。擦掉皮肤上粘结的泥浆也是除去虱子和其他寄生虫的一种好方法。
这就有些荒谬：在泥浆中打滚不会弄脏皮肤，反而可以清洁皮肤。
非洲灌丛野猪（Potamochoerus larvatus）（图片来源：Nick Garbutt/NPL)
另外也不能忘记的是，当提到“猪”这个词时，涌现在人们脑海中的往往是体表几乎没什么体毛的、粉粉的一种动物，其实它是相对近期的一个人类创新。
家猪和其野生亲戚——野猪，都属于猪科动物。猪科动物包括十几个物种，其中包括疣猪、倭猪、大林猪和非洲灌丛野猪等。
基因证据表明，野猪从亚洲和欧洲的谱系被驯化过两次。这些野猪的祖先在约一百万年前开始分化，时间比驯化家猪要早得多，后者发生在约 9,000 年前。尽管长期分离，但亚洲和欧洲的野猪却有着完全相同的外表。
家猪的情况却并非如此。家猪皮色的基因代码极为多变，因此，家猪也就呈现各种颜色和样子。
拉尔森表示，在不到一万年间，人类就让这种多样性大行其道。在 2009 年发布的报告中，拉尔森和同事写道：“人类择优挑选发生罕见突变、在野生环境中会很快消失的基因。”
这样做要花上一阵子时间（图片来源：David Kjaer/NPL）
最后还要必须澄清一个谣言：即被人们津津乐道的一个“事实”，公猪的性高潮可持续 30 分钟。
“跟据对与母猪交配的公猪的实地观察，其交配持续时间通常为 4-5 分钟，但最长可持续到 20 分钟。”
首先要说明的是，公猪或者母猪对此事的感觉（交配时的体验）我们不得而知，所以对猪性高潮的任何看法都是推测。
根据对公猪普遍采用的人工采精方法——“手握采精法（gloved hand）”，公猪射精持续时间似乎的确很长。据 2012 年一项“优秀种公猪”研究，公猪射精的持续时间平均为 6 分钟左右。但公猪个体差别也相当之大，有一只公猪持续射精长达 31 分钟。
我们很难知道，如果没有人为干预，这种持久射精行为是否能够发生，但可能性当然存在。跟据对与母猪交配的公猪的实地观察，其交配持续时间通常为 4-5 分钟，但最长可持续到 20 分钟。
无论性高潮的真相如何，一份关于如何进行人工受精的网络基本资料警告从业者，在公猪射精完成前，不要去打断它，否则会令公猪暴怒。
（责编：友义）
The truth about pigs
By Henry Nicholls,7 October 2024
Reputation: Pigs sleep and root in faeces. Pigs sweat like pigs. Pigs are filthy animals. Pigs are pink. Male pigs can orgasm for half an hour.
Reality: These stereotypes are best explained by poor husbandry. In the wild, boars don't sleep and root in poo, they eat plants. They do wallow in mud but only because it's a good way to keep cool. Domesticated pigs are often pink, but only because we made them that way. Male pigs can ejaculate for minutes at a time.
"I don't eat nothin' that ain't got sense enough to disregard its own faeces." So says Jules Winnfield, the hitman played by Samuel L. Jackson in Pulp Fiction, explaining why he doesn't eat pork.
A group of wild boars at Basel Zoo in Switzerland has become famous for its food hygiene
Had Winnfield taken a moment to think, he might not have been so snarky about pigs. Rabbits happily snaffle their own faecal pellets, to give the relatively indigestible grasses a second passage through their digestive system, but nobody is rude about bunnies.
Wild boars – the ancestral stock from which we have fashioned our domesticated pigs – are omnivores, and not too fussy about what they eat. Yet 90% of their diet is made up of plant matter, so they probably don't have a particular taste for poo.
If a domestic pig occasionally munches on the odd turd, it's most likely because its cramped home makes it hard not to.
In fact, a group of wild boars at Basel Zoo in Switzerland has become famous for its food hygiene.
Boars will wallow in mud, but they probably do it to keep cool
The animals were given apple slices coated in sand. Rather than eating them immediately, they carried them "to the edge of a creek running through their enclosure where they put the fruits in the water and pushed them to and fro with their snouts before eating."
The boars would never do this for clean apples. Even if they were really hungry, they still took the time to wash their food.
Aside from their food choices, pigs also have a reputation for being more generally filthy.
Boars will wallow in mud, but they probably do it to keep cool.
Rubbing off a layer of caked mud may also be a nifty way to remove ticks and other parasites
This is because pigs do not have functional sweat glands, which is worth remembering next time someone claims they are "sweating like a pig". This physiological reality means that pigs are at serious risk of overheating, and muddy water evaporates much more slowly than clean water.
"A pig, like any animal, is going to try to be comfortable," says Greger Larson of the University of Oxford in the UK. "If that means getting dirty to stay cool then that's what it's going to do. It would probably find other solutions but those haven't been provided because you're keeping them in relatively dense pens."
A layer of mud on the skin may serve other purposes too, acting like sun cream to prevent the skin from burning, or as an insect repellent to deter mosquitoes and the like. Rubbing off a layer of caked mud may also be a nifty way to remove ticks and other parasites.
Paradoxically then, wallowing in mud may make for clean rather than dirty skin.
It is also worth remembering that the pink, almost hair-free animal that comes to mind at the mention of the word "pig" is a relatively recent human innovation.
Humans have cherry-picked rare mutations that would be quickly eliminated in wild contexts
Domestic pigs, and their wild relatives the wild boars, are just one member of an entire family of piggy animals called the Suidae. The family includes over a dozen species, from warthogs to pygmy hogs, babirusas, giant forest hogs and African bushpigs.
Genetic evidence suggests that wild boars were domesticated twice, from lineages in Asia and Europe. These ancestral boars began to diverge around one million years ago – long before domestication, which happened around 9,000 years ago. Despite this long separation, Asian and European wild boars have exactly the same camouflaged appearance.
The same cannot be said for domestic breeds. In these pigs, the gene encoding coat colour is immensely variable, and accordingly they display a range of colours and patterns.
We have fashioned this diversity in less than 10,000 years, says Larson. In a paper published in 2009, he and his colleagues wrote that "humans have cherry-picked rare mutations that would be quickly eliminated in wild contexts."
There is one final rumour that has to be addressed: the oft-repeated "fact" that male pigs can orgasm for 30 minutes.
According to observations of males with real sows, copulation duration is typically 4-5 minutes, but can last up to 20 minutes
The first thing to say is that we don't know what sensations the males – or the females for that matter – experience when they mate, so any talk of orgasms is speculative.
But based on the ubiquitous "gloved hand" method used to coax sperm from male pigs, ejaculation does appear to last a very long time. In a 2012 study of "high performance boars", the average duration of ejaculation was around 6 minutes. But there was considerable variation, with one male apparently yielding semen continuously for 31 minutes.
It is difficult to know whether this kind of protracted ejaculation can occur in the absence of the "gloved hand", but it is certainly a possibility. According to observations of males with real sows, copulation duration is typically 4-5 minutes, but can last up to 20 minutes.
Whatever the truth about orgasms, an online primer on how to artificially inseminate pigs warns practitioners not to interrupt the male before he's done, unless they want a very angry pig on their hands. "If you let loose too soon, be prepared for a challenge."