Tool use was once thought to distinguish humans from animal — until, that is, so many animals proved able to use them.

Granted, the fine folks at Leatherman aren't about to be undercut by cheap chimpanzee-manufactured multitools. But it's hard not to feel a species-level déjà vu when seeing a gorilla using a walking stick or capuchin monkey thoughtfully selecting an ideal nut-cracking stone.

Below is a compilation of some of the most interesting animal tool use yet observed. Much more likely remains to be found: until Jane Goodall watched chimpanzees fishing for termites with sticks, scientists had been reluctant to credit animals with such sophisticated behavior — perhaps because, as Charles Darwin noted, “Animals, whom we have made our slaves, we do not like to consider our equal.”

Darwin himself was quite intrigued by animal tool use, suggesting that it allowed them to overcome biological shortcomings. In On the Origin of Species, he noted that elephants snap off tree branches to swat away flies; in honor of Darwin's interest, elephants are the first on our list of animal tool use.

Elephant canteens. Cute YouTube videos of elephant painters show their amazing dexterity, but even more impressive is this peculiar habit: after digging a water hole, elephants will strip bark from a tree, chew it into a ball, then use it to fill the hole. Once the top has been covered with sand, the elephant has an evaporation-resistant canteen.

Image: Flickr/Paul Shaffner

Mole rat masks. The naked mole rat's powerful, protruding teeth are great for burrowing — but digging with their mouths makes it easy to inhale dirt. To keep their lungs clear, the mole rats have been observed placing wood shavings behind the teeth but in front of their lips — a simple face mask. (As an aside, the naked mole rat's better-known cousin has been taught to use a raking device in captivity. A word to raking rat trainers: keep an eye on them! New York City is bad enough without tool-using rodents.)

Video: YouTube/Bh41

https://www.youtube.com/watch?v=C4Tm9QdI_eM

Egyptian vulture hammers. Some say that seagulls who crack open shellfish by dropping them onto rocks are using tools, but that's generally dismissed on a technicality: The seagulls aren't actually manipulating their environment. No such ambiguity surrounds Egyptian vultures, who use rocks to break open ostrich eggs.

Video: YouTube/Gary9209

Burrowing owl bait. In order to attract its favorite beetle prey, burrowing owls collect mammal dung, then spread it around the entrance to their homes.

As with many animal tool behaviors, it's not clear whether the owls are acting out an instinctive sequence of actions, or consciously deciding to collect the dung. Either way, though, those dung balls are tools.

Image: Ronald G. Wolff / Nature

Woodpecker finch, green jay and New Caledonian crow bug-fishing sticks.

All these birds use twigs to forage for insects, but the New Caledonian crow is famed for its cleverness, seen here in a captive bird's fashioning of a food-fetching hook from straight wire.

Video: YouTube/Kivirtual

Chimpanzee clubs. Since Jane Goodall's pioneering observations, chimpanzees have been observed using sticks to spear bush babies, smashing nuts open with stones (which, apparently, they've done for thousands of years) and making straw toothpicks. But their most striking tool may be the club.

Video: YouTube/Everything is Pointless

Gorilla walking sticks. Any hiker knows the value of a good walking stick — and so, apparently, do gorillas. In a swampy forest clearing in the northern Congo, this gorilla used a stick to test the depth of a pool of water, and then to keep its balance as it walked across.

Image: Wildlife Conservation Society/PLoS Biology

Dolphin fishing sponges. An extended family of Indian bottlenose dolphins in Shark Bay, Australia are the first known marine mammal to use tools:

sponges with which they stir ocean-bottom sand, uncovering and disorienting prey. “It’s hard to get inside their heads because their brains are constructed differently and it’s very hard to analyze their language, but they do seem very intelligent,” said Georgetown

University marine biologist Janet Mann to the Times.

Let's just hope dolphins don't develop opposable thumbs.

Image: Ewa Krzyszczyk / PLoS ONE

Multitool image credit: Flickr/Frostnova

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