The Hawaiian crow is the latest animal to be added to the elite group of species that use tools, after scientists documented it employing sticks to extract hard-to-reach morsels of food from crevices in a log in less than one minute.

Its cousin, the New Caledonia crow, was already known to be a master toolmaker and user, and scientists believe that the similar features shared by both species – large, mobile eyes and unusually straight bills – are evolutionary adaptations to enable them to use tools, much like humans having opposable thumbs.

However these remarkable skills are in danger of being lost: the Hawaiian crow is the most endangered corvid species and is already extinct in the wild due to habitat loss and persecution.



While there is no definitive number of species that use tools and there remains some debate about what constitutes tool use, here are just some of the best-documented examples of non-human species using tools:



Sea otters

Each of these marine mammals carries a personal stone in the loose pouch of skin under its foreleg, and uses it to break open hard-shelled prey such as sea urchins, mussels, abalones, clams and snails. It either uses the stone as an anvil by lying on its back and hitting the shell against the stone on its chest, or as a hammer by smashing the stone against abalone to break them free from rocks. Sea otters also employ a range of other tools including driftwood, broken glass and empty shells.

A sea otter uses a rock to open a clam in Monterey Bay, California, US. Photograph: Doc White/NaturePL

Dolphins

The intelligence of dolphins is well-known, but in 2005 a pod of Indo-Pacific bottlenose dolphins in Shark Bay, Western Australia, was seen tearing off pieces of conical sponges to use as tools. By wrapping the sponges over their beaks, they protected themselves from abrasions while stirring the sandy ocean floor to uncover prey. The researchers also believe that this behaviour is passed from parents to their young along mother-daughter lines.

Scientists have discovered Indo-Pacific bottlenose dolphins in Shark Bay off the coast of Australia can apparently can use sponges as tools to get food. Photograph: Eric Patterson/Shark Bay Dolphin Project

Octopuses

Veined octopus off the coast of Indonesia have been seen using coconut shells as tools – scooping up halves, stacking them and transporting them up to 20m across the seafloor where they reassembled them to use as a shelter when needed. The blanket octopus – immune to the sting of the Portuguese man o’war – is known to tear off their stinging tentacles and wield them as a weapon against predators.

Coconut octopus is one of the few cephalopods that is known to exhibit the behaviour of tool-use. Photograph: Mike Veitch/Alamy

Chimpanzees

There have been numerous examples of tool use among chimpanzees since Jane Goodall observed them using sticks to fish termites out of mounds in the 1960s. Sharpening sticks to use as weapons, using stones to crack open nuts and sticks to extract honey are just some of the behaviours scientists have witnessed.

A chimpanzee uses a stick to catch food. Photograph: James Balog/Getty Images

Egyptian vultures

One of this species’ favourite foods is the ostrich egg, which has a hard shell. These vultures take rocks in their beak, rear their head and throw the rock repeatedly at the eggs until the shell breaks. They have been seen selecting round rather than jagged rocks as tools.

An Egyptian vulture holds a stone in its beak to break an egg. Photograph: StockPhotoAstur/Getty Images/iStockphoto

Elephants

Elephants have demonstrated their ability to manufacture and use tools with their trunk and feet. Wild Asian elephants use branches to swat flies or scratch themselves, sometimes modifying the tool to make it more effective. Captive elephants have been seen problem-solving by moving boxes to reach food or dropping rocks on to electric fences to cut supply. One elephant in South Africa was observed digging holes, ripping bark from a tree, chewing it into the shape of a ball, filling the hole with water, covering over it with sand to avoid evaporation, then later going back for a drink.

A Sri Lankan elephant holds a stick in his trunk as a tool. Photograph: Jürgen & Christine Sohns/Getty Images

Woodpecker finch

This finch from the Galapagos Islands has a short beak and tongue, and when faced with prey that is inaccessible, flies off to find a cactus spine to prise insects out of tree branches. It carries the spine from branch to branch and modifies its tools for use in different scenarios.