It's the moment every dog owner instantly regrets ever letting their dog kiss them on the mouth: Watching that very same beloved, seemingly well-trained and civilized¹ pup eagerly devour² a stinky, steaming pile of poop off the sidewalk.

有一个时刻会让养狗的朋友后悔时常嘴对嘴亲狗——狗看似受过良好训练又有礼貌，但是也会吃下路边臭气熏天的热便便。

Ugh, gross! But why? Why?!

好恶心！但是狗为什么会吃便便呢？

It;s a topic that has long perplexed³ animal researchers and veterinarians. And if you Google the topic, you're likely to get more than a dozen different explanations ranging from canine⁴ anxiety to illness to simply boredom⁵.

这个问题困扰动物研究学者和兽医们不止一时半刻。在网上搜搜看，能发现各种不同的解释，有的说因为犬类焦虑症，有的说因为生病，有的说狗只是太无聊了。

However, a new study led by veterinarian Benjamin Hart, director of the Center for Animal Behavior at the University of California at Davis, has managed to link the off-putting behavior to “greedy eating” (dogs that quickly ravish their food bowls, according to owners) as well as an instinct connected to canines⁶’ ancestral wolf pack days.

但是加利福尼亚大学戴维斯分校区动物行为研究中心主任本杰明·哈特做了项调查，将狗这种倒胃口的行为归结为“贪吃”（养狗的人都说狗会迅速抢走饭碗），也与犬类祖先狼的遗留本能有关。

As the Washington Post reports, Hart and his team surveyed over 3,000 dog owners. Of these subjects, 16 percent ate other dogs’ feces “frequently” (their owners had witnessed a crappy chow down session at least six times), and of those pups, 80 percent preferred fresh feces less than two days old. Well, who doesn’t?

华盛顿邮报》报道，哈特和其团队对3000多位养狗人士进行了调查，16%的狗“常常”会吃其他狗的便便（狗主人至少见过六次这样的场景），80%的狗更喜欢两天内的新鲜便便。谁不喜欢新鲜的食物呢？

Interestingly, the research suggested that the tendency towards coprophagia (the scientific term for poop-eating) was evident no matter a dog’s age, breed, diet, house-training status or compulsive behavior tendency. This finding has unleashed⁸ a new theory: Modern day dogs have inherited both their aversion to pooping where they live as well as their likelihood to eat fresh poop from their ancient wolf ancestors.

有趣的是，这项调查显示，年龄、品种、饮食习惯、训练水平、强制行为都不会干扰狗吃便便。这就带来了一个新的理论：如今的狗狗一边在遗传对便便的厌恶，一边又会像狼祖先一样吃新鲜的便便。

You see, wayyyy back in those wild days, wolves may’ve eaten the fresh feces of sick, lame¹⁰ or old members who accidentally let a load loose as a way to clean up inside and around their den⁷. Since it takes about two days for parasites¹¹ and other pathogens to develop, eating fresh poop is not usually dangerous, and in fact, eating poop that was festering in their living quarters was actually a helpful way to avoid intestinal¹² parasites such as larvae¹³ and worms.

看到了吧，在很久很久很久以前，狼也会吃同类的粪便，不管对方是不是老弱病残，不管这坨便便的出现是不是为了清理狼窝。寄生虫和病原体要两天之后才会出现在粪便中，所以新鲜的粪便对食用者来说没什么危险。而且新鲜粪便会在狼的体内溃烂，能够有效避免幼虫和蠕虫寄生在肠道内。

That said, some great minds in the canine scientific community think there may be a bit more to it. For instance, Professor James Serpell of the University of Pennsylvania and editor of the recent book The Domestic Dog: Its Evolution, Behavior and Interactions with People, told theWashington Post he finds the wolf theory “plausible,” but he's also intrigued¹⁴ by the “greedy eaters” survey findings.

犬类研究圈认为好处不止于此。宾夕法尼亚大学教授詹姆斯·斯贝尔（James Serpell），刚刚完成了新书《家犬：进化、行为和与人互动）》，他告诉《华盛顿邮报》，狼理论“有道理”，但是“贪吃”调查的结果也让他很感兴趣。

He referenced a study of free-roaming wild dogs in developing countries that scavenge for food and, as a result, fill up on a sizable amount of human feces. This seems to indicate that poop could be viewed, errr digested, as a second-hand¹⁵ food source.

他举例说，发展中国家的流浪狗在寻找食物时，也会吃掉相当多人类的便便。看起来好像便便是狗寻找食物的第二选择。

Today, dogs (and cats) “are fed diets that are relatively¹⁶ rich in fats and protein, not all of which may be completely digested, making their feces potentially attractive as a second hand food source,” Serpell told the Washington Post.

斯贝尔说，现在的狗（和猫）“都用富含脂肪和蛋白的食物喂养，但是这些食物不一定能全部消化，所以他们的便便就会成为诱狗的食物来源”。

So, there you have it. Poop-eating is probably a normal, evolutionary¹⁷ dog trait.

现在明白了吧，吃便便可能是狗正常进化中的特性。

But, take heart: Hart and his team are working on a solution. They’re currently looking at clinical trials of new methods and products that dissuade¹⁸ your pup from chomping¹⁹ down on their own or others’ droppings.

但是切记：哈特和团队一直在寻找解决方法，试图通过新方法和新产品的临床手段阻止宠物狗食用便便。

The best thing to do, for now, is keep your dog on a short leash⁹ and make sure to pick up your own lawn.

眼下最好的办法是给狗拴上短链，确保自家草坪里没有潜在第二食物源。