Scientists once thought of tool use as a defining feature of humans. That's until examples of tool use came in from other primates灵长目, along with连同一起 birds and an array of一批，大量 other mammals哺乳类. Now, a report in the December 14th issue of Current Biology, a Cell Press publication, adds an octopus章鱼 to the growing list of tool users. The veined有叶脉的，有纹理的 octopus under study manages a behavioral trick that the researchers call stilt walking. In it, the soft-bodied octopus spreads itself over stacked妖艳的，身材丰满匀称的, upright coconut shell椰子壳 "bowls," makes its eight arms rigid, and raises the whole assembly to amble缓行，从容漫步 on eight "stilts" across the seafloor海底. The only benefit to the octopus's ungainly maneuver策略，演习 is to use the shells later as a shelter or lair巢穴，躲藏处, and that's what makes it wholly different from a hermit crab寄生蟹 using the discarded shell of a snail.

"There is a fundamental difference between picking up a nearby object and putting it over your head as protection versus collecting, arranging, transporting (awkwardly), and assembling portable armor as required," said Mark Norman of the Museum Victoria in Australia.

Julian Finn, also of the Museum Victoria, said the initial discovery was completely serendipitous偶然发现的.

"While I have observed and videoed octopuses hiding in shells many times, I never expected to find an octopus that stacks multiple coconut shells and jogs across the seafloor carrying them," he said.

In recalling the first time that he saw this behavior, Finn added, "I could tell that the octopus, busy manipulating coconut shells, was up to something, but I never expected it would pick up the stacked shells and run away. It was an extremely comical滑稽的，好笑的 sight—I have never laughed so hard underwater."

After 500 diver hours spent "under the sea," the researchers observed the behavior of 20 veined octopuses. On four occasions, individuals traveled over considerable distances—up to 20 meters—while carrying stacked coconut shell halves beneath their body.

"Ultimately, the collection and use of objects by animals is likely to form a continuum连续统一体 stretching from insects to primates, with the definition of tools providing a perpetual永久的，不断的 opportunity for debate," the researchers concluded. "However, the discovery of this octopus tiptoeing across the sea floor with its prized coconut shells suggests that even marine invertebrates无脊椎动物 engage in behaviors that we once thought the preserve of humans."