四级英语听力训练短文

四级英语听力训练短文

hat Kind Of Dogs Are Sled Dogs?

In books and movies like Call of the Wild, huge, vicious huskies pull sleds for hundreds of miles over the Alaskan tundra. A Moment of Science wonders, what kind of dogs are sled dogs?

Husky

Most champion sled dogs are not pure husky： in fact, the “Alaskan Husky” isn’t really a breed at all：it’s a mix of various breeds. Although not pure bred, every sled dog must be carefully bred for life on the trail.

The dogs need heavy coats to protect them from the cold, and tough feet to prevent injuries. Unlike the tough dogs in the movies, dogs with softer feet wear booties when they run.

Sled Dogs

The dogs also need compact bodies to maximize endurance. The sled dogs’ remarkable endurance is t hanks to their large heart-to-body ratio, and their ability to carry oxygen from the lungs to the muscles, which is about three times that of a human being

On film, large dogs seem powerful, but their size decreases their ability to use oxygen efficiently. In competitive dog-sledding, dogs usually weigh less than 55 pounds and can comfortably trot over 70 miles a day.

Temperment

A sled dog also needs the right temperament. They must love running and be sociable and obedient. Like wild dogs, each team has a hierarchy, but the dogs struggle for position by taking aggressive or submissive postures such as squealing and rolling. Real dogfights are rare because the dogs are carefully introduced and trained before going out on the trail.

The careful crossing of northern dogs, like Malamutes, with southern breeds like Greyhounds produces dogs with the right stuff to be sled dogs.

雪橇狗是什么品种？

在书里或者在像《野性的呼唤》之类的电影里，巨型凶猛的哈士奇在阿拉斯加的冻原上可驰骋数百英里。《科学一刻》栏目想知道，到底什么样的狗是雪橇狗呢？

哈士奇

绝大部分冠军雪橇狗都不是纯种哈士奇：事实上，所谓的“阿拉斯加哈士奇”根本就不是一个品种，而是由多个品种杂交而成。即使并非纯种，每条雪橇狗在其拉雪橇的生涯中都需精心喂养。

狗狗们需穿戴厚重的保暖服以免受寒，以及拥有强健的足部以防止受伤。与电影里面强壮的狗狗不同，足部柔软的狗狗在奔跑时会穿上短靴。

雪橇狗

狗狗们需要结实的身躯以使自身耐力化。雪橇狗耐力持久，主要是因为它们的心脏对比其身体来说相当之大，并且它们将肺部的氧气供给给肌肉的水平是人类的三倍。

在电影里，体型巨大的狗狗看起来很强壮，而事实上它们的体型弱化了它们利用氧气的水平。在雪橇狗竞技当中，通常体重在55磅以下的狗狗每天能够轻松地慢跑70英里。

性情

雪橇狗需性情温和。他们必须热爱奔跑，温顺友好。正如野狗一样，每个狗群都有头狗，但是狗狗们通过极具侵略性的长吠或者表达顺从的滚地等动作来获取位置。狗狗们混战的机率较小，因为在进入雪橇队之前他们就已经受到了良好的引导和训练。

北方的爱斯基摩狗与南方品种如长腿猎狗等交配得当，那么他们的后代将具备成为雪橇狗的优良基因。