During the 20th century, the blue whale population dropped to less than one percent of its original number. This was due to hunting on an unimaginable scale. Between the years 1930 and 1931, over 29,000 blue whales were killed around Antarctica alone, and the slaughter of blue whales continued in this magnitude right up until 1966, when hunting blue whales was banned by the International Whaling Commission. Despite the ban, threats to the dwindling blue whale population continue to come from many different angles.
The blue whale's only natural predator, apart from humans, is the orca, or killer whale. Though orcas don't seem to be able to kill blue whales in a single attack, which is unsurprising due to the colossal size of the blue whale, they can cause wounds that prove fatal over a long period of time. Studies have shown that up to a quarter of all mature blue whales have scars resulting from fights with orcas. Blue whales may also suffer wounds from colliding with ships or becoming entangled in fishing lines.
In addition to suffering injuries due to encounters with modern seafaring vessels, one of the blue whale's most extraordinary characteristics may also be under threat from a seemingly innocuous modern technological advancement. Sonar, used by many marine vessels to navigate and detect underwater objects, may be having an adverse effect on the blue whale's ability to communicate with low frequency sounds. Scientists have discovered that the whale stops emitting certain calls notifying other whales of food sources when mid-frequency sonar is set off. The current worldwide population of blue whales stands between 5,000 and 12,000, and blue whales are officially recognized as an endangered species.
1. How do blue whales separate krill from water?
(A) They use their long bodies.
(B) Their arteries are the size of small caves.
(C) There are long plates coated in bristles in their mouths.
(D) They take their time because they are solitary creatures.
2. What does the phrase epic proportions mean?
(A) Myths and legends.
(B) Largeness on an almost unimaginable scale.
(C) Historical scenes.
(D) Heroes of the sea.
3. What caused the massive drop in blue whale population?
(A) Orca attacks.
(B) Sonar.
(C) Fishing lines.
(D) Excessive whale hunting.
4. Which of the following is NOT true about blue whales?
(A) They are no longer considered endangered species.
(B) They can communicate using low frequency sounds.
(C) Many adult whales have scars from orca attacks.
(D) Over 290,000 whales were killed in 1930 and 1931.
在 20世纪期间，蓝鲸的数量下降到连原本数量的百分之一都不到。这是由于令人想象不到的大规模猎杀所造成。1930到 1931 年间，光是在南极洲周围就有 2 万 9 千多头蓝鲸被猎杀，而对蓝鲸如此大量的屠杀情况一直持续到 1966 年国际补鲸委员会禁止猎杀蓝鲸为止。尽管有此禁令，但对于日渐减少的蓝鲸族群的威胁仍持续自四面八方而来。
除了人类之外，蓝鲸唯一的天敌就是虎鲸，或称为杀人鲸。虽然虎鲸似乎无法在一次攻击中就杀掉蓝鲸，鉴于蓝鲸的体型这点并不足为奇，但虎鲸造成的伤口经过很长一段时间后却证实是致命的。研究显示多达四分之一的成年蓝鲸身上都留有和虎鲸打斗而导致的伤疤。另外蓝鲸也可能因为和船只碰撞或是被钓鱼线缠住而留下伤口。
除了因为遭遇现代航海船只而受伤，一个看似无害的科技进展也可能使蓝鲸最特别的一项特性受到威胁。许多海洋船只利用声纳来导航及侦测水底物体，而这项技术对蓝鲸以低频率声音来沟通的能力可能产生不利的影响。科学家发现，人类发出中频声纳时，鲸鱼会停止对其他鲸鱼发出通知食物来源的呼叫。目前全世界蓝鲸数量在 5 千头到 1 万 2 千头左右，而蓝鲸已被公认为濒临绝种的物种。
答案： 1. C 2. B 3. D 4. A
鲸须，由鲸须板和鲸须毛组成，是指须鲸亚目下属的鲸类上颚所延伸下来的梳子状的板片，用来取代牙齿，从上颚垂下，排在须鲸口部的两边。须鲸用鲸须来滤食海水中的浮游生物和其他动物。
须鲸首先会张开大口，将大量海水吞入口腔，其中就有须鲸赖以维生的浮游生物、磷虾和小鱼。待吞入后，须鲸半闭口，将自己的舌头顶向上颚，将口中的海水压出口腔，而浮游生物等则会留在鲸须或口内，此时鲸鱼会将剩下的食物吞掉。（数据源：维基百科）
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