对北极熊来说，近来好运气并不多，也似乎相当遥远。北极海冰正以惊人的速度在融化。雪上加霜的是，今年早些时候科学家宣布，污染可能会弱化北极熊的阴茎骨。然而，还有一线希望。这些动物自古以来就依靠夏季海冰来捕猎环斑海豹，但最近的海冰融化迫使一些北极熊在陆地上度过夏天，那里很难接近海豹。科学家们曾经提出，这些“上岸熊”因此陷入了一种被称为“行走冬眠”的半麻木状态来节省能量，从而逃避饥饿。但一项新的研究表明，特别保护可能并不存在。在2008年至2009年间，研究人员标记并追踪了43头北极熊，随之测量了岸熊和冰熊(那些在剩余的海冰上度过冬天的北极熊)在夏天的活动程度和体温的变化。他们发现，这两个熊群的活动和体温都有一定跌幅，但同冬眠期间的大幅下滑完全不同。随着日渐消失的夏季海冰迫使北极熊在越来越少的食物中寻求更长的生存时间，这些生理特征的变化(即活跃程度和体温的稍作下降)可能无法保护北极熊对抗饥饿，研究人员今天在《科学》杂志的网络版上报告说。（相关阅读：Science：冬眠中的熊如何保持骨骼强壮）

原文链接：

Polar bears can't hibernate their way out of starvation

原文摘要：

For polar bears, lucky breaks are few and far between these days. Arctic sea ice is melting at an alarming rate, and to add insult to injury, earlier this year scientists announced that pollution may be weakening the bears’ penile bones. There was, however, a glimmer of hope. The animals have historically relied on summer sea ice to hunt ringed seals, but the recent melting has forced some bears to pass the summer on land, wher access to the seals is limited. Scientists had proposed that these “shore bears” fell into a state of semitorpor called “walking hibernation” to save energy, and thus be shielded from starvation. But a new study suggests that the special protection may not exist after all. After tagging and tracking a total of 43 bears between 2008 and 2009, researchers measured how the activity levels and body temperatures of both shore and ice bears—those that spend the season on what’s left of the ice—changed over the summer months. They found that both groups experienced similar moderate declines in activity and body temperatures, far different from the sharp dro that occurs during winter hibernation in other bear species. As the disappearing summer sea ice forces the bears to survive longer and longer with less food, those modest declines are likely to offer little protection against starvation, the researchers report online today in Science