Sea otters get more prey and reduce tooth damage using tools
海獭可以获得更多的猎物，并使用工具减少牙齿损伤
May 15 Humans are not alone in the use of tools. Chimpanzees, for instance, crack nuts with stones and use sticks to get at tasty termites. Dolphins are known to employ sponges to protect their beaks while foraging. And a Galapagos Islands finch uses cactus spines to dig grubs out of holes.
5月15日人类并不是唯一使用工具的人。例如，黑猩猩会用石头敲碎坚果，用棍子来捕食美味的白蚁。众所周知，海豚在觅食时会用海绵来保护它们的喙。一只加拉帕戈斯群岛的雀用仙人掌的刺从洞里挖出幼虫。
Sea otters also are members of the animal kingdom’s tool-wielding club. And a new study offers a fuller understanding of the tool use – utilizing rocks and other objects to break open hard prey – by these marine mammals. It lets the otters eat certain larger prey and reduces their tooth damage by cutting down on their chomping down on hard shells, with females using tools more than males, perhaps to compensate for their smaller body size and weaker bite force, researchers found.
海獭也是动物王国使用工具俱乐部的成员。一项新的研究提供了对这些海洋哺乳动物使用工具的更全面的了解—利用岩石和其他物体来打破坚硬的猎物。研究人员发现，这让水獭吃某些较大的猎物，并通过减少它们对硬壳的咀嚼来减少它们的牙齿损伤，雌性比雄性更多地使用工具，这可能是为了弥补它们较小的体型和较弱的咬合力。
The researchers observed 196 southern sea otters along the central California coastline – Big Sur, Monterey, San Luis Obispo, Piedras Blancas and Elkhorn Slough.
研究人员观察了沿着加州中部海岸线的196只南方海獭——大苏尔、蒙特雷、圣路易斯奥比斯波、彼德拉斯布兰卡斯和斯劳的埃尔克霍恩。
When not crushing prey with their teeth, the otters float on their backs when feeding and use rocks, shells and discarded bottles as hammers or anvils to smash open hard-shelled prey, also sometimes bashing prey onto the surfaces of docks and boats.
当它们不用牙齿压碎猎物时，水獭在进食时会浮在背上，并使用岩石，贝壳和废弃的瓶子作为锤子或铁砧来砸开硬壳猎物，有时也会将猎物撞到码头和船只的表面。
Among the prey were sea urchins, abalone, crabs, mussels, clams, snails and fat innkeeper worms. The shells of certain larger prey would be too tough, without tools, to break to gain access to the edible soft parts inside. For instance, mussels, clams and snails would otherwise be unavailable.
猎物中有海胆、鲍鱼、螃蟹、贻贝、蛤蜊、蜗牛和肥胖的旅店老板蠕虫。某些较大的猎物的外壳太坚韧，没有工具，无法打破以获得内部可食用的柔软部分。例如，贻贝、蛤蜊和蜗牛，否则将无法获得。
“Tool use allows individuals to maintain energetic requirements through the processing of alternative hard prey that are typically inaccessible with biting alone, suggesting that this behavior is a necessity for the survival of some otters in environments with limited resources,” said evolutionary biologist Chris Law of the University of Texas and University of Washington, lead author of the study published on Thursday in the journal Science, opens new tab.
“工具的使用允许个体通过处理替代的硬猎物来保持能量需求，这些猎物通常是单独咬无法获得的，这表明这种行为是一些水獭在资源有限的环境中生存的必要条件，”德克萨斯大学和华盛顿大学的进化生物学家Chris Law说，他是周四发表在《科学》杂志上的研究的主要作者。
The frequency of tool-use behavior varies, with some otters doing it more than 90% of the time when feeding and others rarely or never, according to study co-author Rita Mehta, a University of California, Santa Cruz functional and comparative biologist.
研究报告的合着者、加州大学圣克鲁斯功能和比较生物学家丽塔？梅塔（Rita Mehta）表示，水獭使用工具的频率各不相同，有些水獭在进食时90%以上的时间都在使用工具，而有些水獭很少或从不使用工具。
Tool use was particularly important for the female otters.
工具的使用对雌水獭来说尤为重要。
“Females need the calories. They are smaller than males, and pregnant or nursing females have elevated caloric demands. Tool-using females were shown to consume a greater proportion of very large prey to help them meet their caloric needs,” Mehta said.
“女人需要卡路里。他们比男性小，怀孕或哺乳的女性有较高的热量需求。使用工具的雌性被证明消耗更大比例的非常大的猎物，以帮助他们满足他们的热量需求，“梅塔说。
The southern sea otters, a subspecies also called the California sea otter, can reach up to four feet (1.2 meters) long. Males weigh up to about 70 pounds (32 kg) and females up to about 50 pounds (23 kg).
南方海獭，一个亚种也被称为加州海獭，可以达到4英尺（1.2米）长。雄性体重可达约70磅（32公斤），雌性可达约50磅（23公斤）。
Eating hard-shelled prey, as the otters do, can lead to broken teeth.
吃硬壳的猎物，就像水獭一样，会导致牙齿断裂。
“Without their teeth, otters can’t eat and will die. Females show slightly less damage to their teeth overall, probably because of their increased tool use,” Law said.
“没有牙齿，水獭就不能吃东西，会死的。女性的牙齿总体上受到的伤害略少，可能是因为她们使用的工具增加了，”劳说。
Sea otters, the largest member of the weasel family, generally eat food equal to about a quarter of their body weight daily as they prowl kelp forests and seagrass beds. The population of southern sea otters along California’s coastline numbers only about 3,000.
海獭是黄鼠狼家族中最大的成员，当它们在海藻森林和海草床中徘徊时，通常每天吃的食物相当于它们体重的四分之一。加州海岸线上的南方海獭沿着的数量只有大约3000只。
The otters were opportunistic in terms of their tools.
水獭在工具方面是机会主义的。
“Otters are intelligent mammals, and they are very strong. People who live along the bay commonly observe otters using a variety of human-discarded material as tools, from glass bottles to pieces of plastic, so otters seem flexible in what they may try to use to break open prey,” Mehta said.
“水獭是聪明的哺乳动物，它们非常强壮。生活在海湾沿着的人们通常会观察到水獭使用各种人类丢弃的材料作为工具，从玻璃瓶到塑料片，所以水獭似乎很灵活，他们可能会试图用什么来打破猎物，”梅塔说。