- Otters have a special pocket in their fur for storage
- They have been found to keep the same rock in their pocket for months or years
- Few animals are known to use tools as otters do
Otters are renowned for their intelligence in using rocks as tools, but now it seems that once they get one that they like, they stick with it.
Researchers have found that otters will keep a particular rock in a special pocket in their fur for months or even years. This rock will be used for cracking shells of prey they have caught.
Carefully selected
While scientists are not completely sure about why otters do keep one particular rock, they think it could be down to practicality – once you have a tool you like, why would you give it up? Scientists think this is more likely than they have an emotional attachment to a particular rock.
Sea otters are thought to select the rocks they keep carefully. They usually plump for rocks that are large enough to be effective in cracking shells and the like but small enough to fit in their pocket easily.
By using a rock as a tool, it helps them to quickly open shell-based prey and saves them having to use their teeth instead and wearing them down.
Female otters most likely to use rocks
Females have been found to be more reliant on using rocks as tools as they are smaller than their male counterparts and therefore do not have as strong a bite, meaning they find it more difficult to crack open shells with just their teeth. But by using a rock, they can crack open larger prey, which can be significant if they are mothers raising pups and therefore require more food.
Mothers can also help to show pups how to use such tools and keep ones they like. Otters aren’t born with an instinct to use tools – it is something that they learn from their mothers during the first few months of life.
The use of tools is relatively rare among animals. Various types of primates are known to use tools such as rocks and sticks to get into foods, but many other animals do not. Some birds use tools such as crows and parrots too.
However, otters still face threats from multiple sources, such as hunters – who value their fur – pollution, destruction of their habitat and climate change.
