使用工具的熊:聰明背後是進化的跡象嗎?

Smarter than the average bear: The first case of ursine tool use.

一隻特別聰明的熊：第一隻會用工具的熊。

PRIMATES apart, few mammals employ tools. Sea otters use rocks to smash clams open, dolphins wrap sponges around their noses to protect themselves while they forage on the seabed, elephants swat insects with branches and humpback whales exhale curtains of bubbles totrap schools of fish. Until now, these four examples had been thought the extent of the non-primate mammalian tool-users club. But a study just published in Animal Cognition, by Volker Deecke of the University of St Andrews, in Britain, has added a fifth and rather surprising one. That epitome of rugged wildness, the grizzly bear, seems to be the only species other than humans to have invented the comb.

除了靈長類動物，會使用工具的哺乳類動物屈指可數。海獺會在石頭上砸開蛤蜊;海豚在海牀上覓食時，會將海綿綁在鼻子上以保護自身;大象會用樹枝拍打昆蟲;駝背鯨會呼出陣陣氣泡來困住魚羣。至今，人們仍認爲非靈長類動物中只有這四種會使用工具。但英國聖安德魯大學的Volker Deecke在《動物認知》上剛發表的研究指出了第五種會用工具的動物，而且是令人相當意外的一種。粗獷野性的象徵——灰熊，看來是除了人類以外唯一一種發明了梳子的動物。

Dr Deecke made this discovery while studying grizzly-bear behaviour from a small boat in GlacierBay National Park, Alaska, on July 22nd 2010. After a period of play-fighting with another bear and a short bout of feeding on a beached whale carcass, a bear of between three and five years of age, sex unknown, waded into the shallows of the bay. Once there, it picked up a fist-sized rock and carefully rotated it for about a minute before dropping it back into the water. Moments later, it picked up another, of similar size, and again rotated it. This time, rather than discarding the stone, it held it against its muzzle and started to rub. Using its left paw to press the rock against its skin and its right paw to support the rock's weight, the bear rubbed away at its muzzle and face for roughly a minute before dropping the stone back into the water. Then it grabbed a third stone of the same size, rotated it and rubbed its face, muzzle and neck for a further two minutesbefore discarding it. This done, it spent two minutes grooming its right paw with its teeth before returning to the whale carcass.

這一點是Deecke博士於2010年7月22日在阿拉斯加冰河灣國家公園一艘小船上研究灰熊習性時發現的。一隻灰熊(年齡3-5歲，性別未知)在與另一隻熊打鬧了一陣並吃了一點被衝到沙灘上的鯨魚屍體後，涉水來到了海灣的淺灘中。在那，它撿起了一塊拳頭大的石頭，小心翼翼地旋轉了約一分鐘後，將其扔回水中。片刻之後，它又撿起了另一塊差不多大小的石頭旋轉起來。但這次它沒扔掉石頭，反而把石頭放到口鼻處開始來回磨蹭。那隻熊用左掌將石頭按在皮膚上，用右掌託着石頭，將石頭在口鼻和臉上蹭了大約一分鐘後纔將石頭扔回水裏。然後，它撿起第三塊同樣大小的石頭並在旋轉後用來磨蹭臉、口鼻和脖子將近兩分鐘後將其扔掉。做完這些後，它又花了兩分鐘用牙齒來梳理右掌的毛，之後便回到鯨魚屍體處。

Dr Deecke found, upon close examination of his photographs, that all three rocks were encrusted with barnacles and he reckons these were acting as the functional equivalent of the teeth of a comb. He thinks the bear was probably using its makeshift combs for comfort, rather thanvanity. But crucially for the concept of tool-use, the animal's rejection of the first rock it picked up shows a discriminating understanding of what was required to get the right amount of scratching from a comb; which rock, in other words, was the tool for the job.

Deecke博士在仔細研究所拍照片後發現，那三塊石頭上都粘有藤壺，而他認爲這些藤壺的功能梳齒一樣。Deecke博士認爲，那隻熊自制梳子可能是想讓自己舒服，而不是爲了美觀。但是，那隻熊沒有用它撿到的第一塊石頭，這說明它有能力判斷子什麼樣的梳子纔好用;換言之，就是哪塊石頭可以拿來當梳子。這一點對判斷動物是否會使用工具至關重要。

An important question from a biological point of view is whether this animal's behaviour is unique. Other tool-using mammals are social species. That means one individual's chance invention is easily copied by others of its group, resulting in a primitive culture. Grizzly bears have not been considered particularly sociable in the past, but if others in Glacier Bay are seen combing themselves in this way that view might have to change. It might, though, be that Dr Deecke's preening animal is unique. That would suggest it came up with the idea of using rocks as combs by itself, rather than copying someone else-truly smarter than the average bear.

在此，有一個很重要的生物學問題：是不是隻有這一隻熊會使用工具?其他會使用工具的哺乳類動物都是羣居動物，也就是說個體偶然的發明很容易被羣體裏的其他成員模仿，從而形成原始的文化。過去，人們並不認爲灰熊具有明顯的羣居特徵，但如果冰河灣有其他灰熊被發現使用這種方法梳理毛髮，那上述觀點就可能會被推翻。不過，也有可能只是Deecke博士看到的那隻梳理毛髮的熊比較特別罷了。那就意味着這隻熊拿石頭當梳子是自己的原創，並非模仿——果然是隻特別聰明的熊。