Hordes of giant mice are devouring endangered seabird chicks on a remote South Atlantic island and may be pushing some of the birds to extinction, scientists report.
The carnage has harmed the breeding success of endangered Tristan albatrosses and threatened Atlantic petrels on Gough Island, a British territory a thousand miles (1,600 kilometers) off the coast of South Africa.
The birds' sole breeding ground is home to 22 bird species—10 million birds in total—and is considered the world's most important seabird colony.
Common house mice were introduced to the island more than a century ago. Now three times larger than normal mice, the invasive rodents likely number more than a million.
Video cameras revealed one pack of ten mice feeding on a Tristan albatross chick's wounds as it nested on the ground. Footage also showed mice devouring Atlantic petrel and great shearwater chicks.
The birds did not fight off their attackers, even as some mice fed inside the body cavity of one albatross chick.
Researchers say the footage provides the first hard evidence that mice previously thought harmless to seabirds are willing to attack prey more than 300 times their weight.
"Like a House Cat Attacking a Hippo"
Nearly three feet (one meter) tall, a Tristan albatross chick can weigh up to 22 pounds (10 kilograms), or about as much as a turkey. Gough Island mice weigh just 1.2 ounces (35 grams) on average.
Geoff Hilton, a U.K.-based biologist with the Royal Society for the Protection of Birds and study co-author, has compared the mismatch to a house cat attacking a hippopotamus.
Hilton and his colleagues say that while the seabird chicks can defend themselves from other birds, the chicks don't appear to be programmed to fend off novel predators like mice.
Ross Wanless, a Ph.D. candidate at the University of Cape Town, led the study, published in the online edition of the journal Biology Letters.
"The mice on Gough are amongst the biggest wild house mice in the world. In winter, they eat through the 'island larder' until they start to run out of seeds and invertebrates," he said.
"At that point they increasingly start to eat seabirds, as well as other mice. A Gough winter is not a nice place to be a seabird or a mouse."
Wanless says Gough Island mice are depressing bird populations and will cause some species, such as the Tristan albatross, to go extinct if left unchecked.
The researchers believe mice become predatory when other introduced animal pests, such as rats and cats, are eliminated, freeing the mice from competition and predation.
While small in area, ocean islands sustain the world's highest diversity of bird species, the researchers note, adding that over the past four centuries, 90 percent of global bird extinctions have involved island species.
Many such extinctions have been caused or aggravated by rats, cats, and other introduced animal pests.
The researchers say that in light of their new evidence, island restoration programs should also target mice.
译文:
巨鼠吞吃海岛上的鸟类幼雏，使其濒临灭绝
据科学家报告，在一个偏僻的南大西洋岛屿上，大群巨鼠吞吃濒危海鸟的幼鸟，并可能迫使部分的鸟类濒临灭绝。
这一大屠杀，妨碍了濒危的特里斯坦信天翁的成功繁殖，并威胁到大西洋戈夫岛上的海燕；戈夫岛是英国领土，离南非海岸一千英里（ 1600公里）。
这一鸟类的唯一繁殖地，有22个鸟种，总共约1千万只鸟，被认为是世界上最重要的海鸟聚居地。
一个多世纪前，普通家鼠被引进到该岛；现在它们比正常老鼠大三倍。这些入侵啮齿类动物可能有100多万只。
摄录机显示，10只老鼠正成群地啃食特里斯坦信天翁幼雏的伤口，因为幼雏是在地上筑巢的。画面还显示，老鼠吞噬大西洋海燕和大海鸥类飞鸟的幼雏。
甚至当有些老鼠在吃信天翁幼雏的内体腔时，这些鸟都没能击退他们的攻击。
研究人员说，该画面提供了第一个铁的证据，证明原先认为对海鸟无害的老鼠现在愿意攻击比自己重300倍的猎物。
“就像家猫袭击河马。”
特里斯坦信天翁幼雏将近3英尺（约一公尺）高，重 22磅（ 10公斤），大约与一只火鸡一样重。戈夫岛上的老鼠平均体重只有1.2盎司。
16日，一名英国皇家鸟类保护学会的生物学家、研究的合作者乔夫希尔顿，将其与家猫袭击河马进行了比较。
希尔顿和他的同事们说，尽管海鸟的幼鸟能保卫自己免受其它鸟类的袭击，这些幼鸟的遗传物质中，似乎没有击退像老鼠这样新奇的掠夺者的编码。
开普敦大学的博士学位候选人罗斯万利斯领导这项研究，在生物学通迅的在线版上发表了研究结果。
“戈夫岛上的老鼠是世界上最大的野生家鼠。冬天，它们吃“岛上食品库”，直到它们没有种子和无脊椎动物可吃。”他说。
“这时，他们愈发吃起海鸟以及其它老鼠。戈夫岛冬天对于海鸟和老鼠都不是一个好地方。”
万利斯说，戈夫岛上的老鼠是令人沮丧的鸟类种群，如果不加以控制，会造成如特里斯坦信天翁等一些物种的灭绝。
研究者认为，当引进的其它有害动物（如大老鼠和猫）被除去时，老鼠失去天敌和竟争而成为掠夺者。
虽然海洋岛屿面积小，却维持着世界上最高的鸟类物种多样性。研究人员说，在过去4个世纪中，全球鸟类灭绝的90 ％涉及到岛屿鸟种。
许多这类灭绝事件是由大老鼠、猫和其他引进的有害动物造成或加剧的。
研究者们说，根据他们提出的新证据，岛屿重建工程还应着眼于老鼠。