Not all otters use tools, but sea otters use them all the time. They typically use rocks and empty shells to feed on marine snails, crabs, sea urchins and mussels. There are only a handful of non-primate species known to use tools, including dolphins and octopuses.
Check out this amazing video of incredibly cute otters using rocks to break open their food:
Why do otters juggle rocks?
Sea otters have many ways of tugging on our heartstrings. And going by a plethora of YouTube videos, we can now add juggling rocks to the list. To be fair, it’s more keepy-uppy than juggling, albeit keepy-uppy with two or three rocks at a time.
The otters lie on their backs and pat the stones into the air, catching them and rolling them skilfully around their chests and necks. And very impressive it is, too – they can even do it with their eyes closed. The behaviour is likely to be linked to the animals’ use of rocks to detach prey from the seabed and break it open. Recreational juggling may be a playful way of learning how best to manipulate these tools.
Why do sea otters always a carry a stone with them? Because otters actually form attachments to certain stones – keeping them in an armpit when not in use – and have been known to retain their favourite ones throughout their lives, which is definitely one of our favourite sea otter facts!
Many otters eat tough food, particularly sea otters that inhabit the shallow coastal waters of the northern Pacific. They’re renowned for preying on hard-shelled marine invertebrates, including abalones, sea urchins, clams, mussels and crabs, usually fracturing the shells with their teeth.
A sea otter can consume up to 11kg of food every day to support its high metabolism – that’s about a quarter of its own body weight! The energy demands of a sea otter mother increases by 17 per cent after giving birth.
A recent study has revealed that sea otter tooth enamel is much tougher than that of humans, helping to prevent their teeth from being chipped when cracking into the prey using their high bite force. The animal’s enamel contains additional layers of a protein-rich gel that works to prevent cracks from spreading.
However, when tackling species with the heaviest armour, such as as marine snails and thick-shelled bivalves, sea otters often employ tools. They typically use a rock as an anvil and repeatedly bash their prey against it until the shell cracks open, then extract the meat from the shell with their canines.
Indeed, research suggests that the sea otter’s bite force may not be sufficient to open the hardest-shelled prey items, hence their use of tools. In fact, sea otters are one of the only mammals (apart from primates) to have developed tool use.
The answer varies by species and location. Eurasian otters have staged a remarkable comeback in the UK, where they’re now once again present in every single county. But habitat loss and hunting have brought many populations of other otter species crashing down around the world, especially in more tropical locations.
North American sea otters are something of a recent success story after they were brought close to extinction in the 19th century, widely hunted for their fur. This was stopped by the establishment of the International Fur Seal Treaty in 1911. Populations in Canada and California are now doing well.
Otters live in a wide variety of watery locations, from the mighty Amazon to the heart of Singapore. But the sea otter’s habitat is unique, as they only live in shallow coastal waters in the North Pacific ocean.
As predators that are near the top of the food chain, otters are hugely important for keeping their environments balanced.
Research has shown that sea otters are vital to the health of carbon-absorbing kelp forests. They prey on sea urchins that feed on kelp. In environments where sea otter populations have been reintroduced, tall kelp forests are flourishing.
A sea otter’s pelt is the thickest of any mammal. It is made up of a waterproof top layer and a short underlayer, which can contain as many as one million hairs per square inch. This makes up for its lack of blubber in the cold Pacific water.
Even a baby sea otter can stay warm on the open ocean, but they do need some help from their mothers.
How do otters cope in winter?
Winter brings many challenges for Eurasian otters. The species has no seasonal fur variation, so expends far more heat and energy swimming and diving in colder waters despite its dense, double-layered coat.
A daily food intake of 15–20 per cent of body weight is key to survival, and otters adapt their patterns of predation and hunting behaviour to make the most of the prey available during these leaner months.
Scottish coastal otters, for example, which usually forage and hunt throughout the day in summer, instead seek prey more intensively in the mornings (though, interestingly, camera-traps set by the International Otter Survival Fund have revealed that they are in fact also active at night).
Winter brings many other dangers to otters. If conditions are mild and wet, cubs can drown in flooded holts. Swollen, murky waters also make swimming more difficult, forcing the animals onto busy roads. You can see why only 50 per cent of youngsters survive to see the spring.
Are sea otters good parents?
Sea otters give birth in water. Most females have only one pup at a time. The mother will produce milk, hunt and teach the pup how to dive for food until the youngster is five to eight months old and can fend for itself.
Many species of river-dwelling otter can swim quite quickly – they have to be strong swimmers to catch fish and fight the flow of the river. With the giant otters of the Amazon growing up to 2m in length, you can imagine that they can swim pretty speedily when they want to!
More surprisingly, sea otters are quite slow swimmers, although they are extremely agile. They spend the majority of their lives on their backs, only flipping over onto their fronts when greater speed is required. To swim faster they use their webbed feet for propulsion and undulate their bodies.
Sea otters can reach 9kph underwater, North American river otters are faster at 11kph, and the maximum speed of the giant river otter is an impressive 14kph. And you definitely don’t want to mess with giant otters, just check out this clip below!
Do otters live alone?
It’s not unusual to see a mother otter with her cubs, but families aside, it depends on the species. Many are mostly solitary apart from the breeding season, whereas others live in groups all year round.
The most gregarious by far are sea otters, which are polygynous (males mate with multiple females). While mothers and pups are usually solitary, sea otters can form social groups of up to a few dozen. When on water, these groups are called rafts, and the largest one ever recorded contained up to 2,000 sea otters.
Why are coastal otters more visible than river otters?
Healthy river systems in the UK may boast equally vibrant populations of otters as typical coastal habitat, but riparian otters are usually harder to spot due to high levels of human and dog disturbance, dense vegetation and the fact that it is more challenging to see otters hunting in fast moving rivers than on the sea.
Coastal otters frequent intertidal zones in search of blennies, eels, rockling, crabs and other crustaceans, and are easy to spot when on the shore. What’s more, these coastal otters live their lives according to the tides, while river otters are usually most active at night.
Otter watching involves perseverance. On a river it is vital to check for signs during winter when the vegetation has died back. These include spraint sites on exposed roots and stones, worn slides on muddy banks and tracks showing five webbed toes.
There are 13 otter species around the world, including the giant river otters, North American river otter, Asian small-clawed otter, European otter, Japanese river otter and African clawless otter, as well as many less well known species.
Some of them are quite common and easy to see in the right places, but others are extremely rare and very difficult to find. You can learn all about them here – Otters of the World.