Otters of Loch Sunart
Discover the Eurasian otter and their habits
There should be no other species, animal or plant, to start our look into local flora and fauna than the otters of Loch Sunart. And no better day to start than on World Otter Day (27th May) which is also Otter Adventures’ birthday (2017)! That is pure coincidence. Honestly!
Many people, myself included when I came here on holiday in 2015, thought we would find quite large Sea Otters in Loch Sunart as it is predominantly salt water here.
It turns out that the perception that any species other than the Sea otter (Enhydra lutris) could live in salt water is incorrect and it is the smaller, more widespread Eurasian otter (Lutra lutra) that resides here. While they are not considered a marine mammal since they require access to fresh water sources, they are well adapted as you shall see if you read on.
Characteristics of our otters
Eurasian otters are a top predator and members of the Mustelidae family, so are related to the Pine Marten, Stoat, Mink, Badger and even Wolverine!
Generally they are around 60 to 90 cm plus a tail of between 30 and 50 cm; the males are noticeably bigger and at the top end of these figures and can weigh around 10 kilograms. To put this in perspective, a male Sea otter can be as long as 1.5 meters plus its tail and weigh up to around 45 kilograms.
Their short limbs and webbed feet make it well adapted to life in aquatic environments. In our clean waters their acute sense of smell, sight and hearing no doubt help it detect prey as well as any threats/disturbance. When underwater, they can close their ears and nose reducing the number of sense available and bringing their highly sensitive whiskers into play to help them detect prey in the murky water.
Two layers of thick fur help Otters waterproof themselves (the outer layer) and keep warm (inner layer) by trapping air to act as insulation.
They are a very solitary animal and tend not to associate with other adults except for reproduction. Throughout much of the areas where Eurasian otters are found they have been noted as being nocturnal (active at night-time) although a study in Shetland (1995) discovered them to be entirely diurnal (active during the day). This may be related to the length of daylight available as you travel further north, especially in winter, but also could be linked to the activity of their prey. Marine species are more vulnerable during daylight hours and also influenced by the height of the tide.
The Eurasian otter is very adaptable and lives in wide range of aquatic habitats, including up to 4,120 meters above sea level in Tibet! The shores of Loch Sunart with its wooded and rocky shorelines are an ideal habitat. Cavities around tree roots and rock piles may make ideal locations for their holts. In these coastal and salt-water areas the numbers of otters has been found to correlate very well the presence of fresh water. The mouth of the Carnoch River and the Strontian River are one of the favoured places for our local otters and the numerous small burns flowing in around the head of the loch further reduce the salinity and give places to wash their fur, drink and possibly catch food.
Most of their activity is centred on a relatively narrow strip on either side of the interface between land and sea. This living space is more pronounced on linear watercourses where they may range 3-5 km, perhaps as much as 40 km. On coastal settings, especially in relatively narrow lochs, the female’s territory may only be one kilometre or so, but is likely to overlap other otter’s ranges. The male ‘dog’ otter are more territorial and extend across at least two female ranges.
Not surprisingly, fish make up around 80% of their diet and they are most active when there is likely to be a high level of fish activity and when they may be corralled into smaller areas. They will also eat a high percentage of crustaceans in coastal areas. They may occasionally take water birds or amphibians, but this is more common in freshwater environments.
We can certainly tell whether our local otter has caught a crab or a fish by what it does when it reaches the surface. If it has a crustacean, it usually rolls on its back and munches it on the water. Fish seem to require a different approach and the otter will usually swim straight for the beach and a safe spot, camouflaged among the seaweed, to much nosily on it.
Reproduction / Young
Otters can mate at any time of year although it is quite common for them to have their young between May and August after a nine-week gestation period. Between one and three cubs are common and are born in a holt in a bank, or between rocks and trees roots. At birth the cubs are around 12 cm long but grow quickly.
The cubs are not natural swimmers. They are often afraid of the water and when they do get into the water their fluffy coats hinder them. For these reasons, their mother’s often have to drag them into the water at around 10-16 weeks of age and help them rapidly develop their fishing and hunting skills.
Typically they will leave the protection of their mothers at between ten and twelve months and can breed from around two years. Their life expectancy in the wild is generally around four years, but may rarely live to between 8 and 12 years (Marine Conservation Society).
In part two of our otter-ly amazing (sorry) blog that we will upload soon, we'll take a look at how to find, spot and identify otters while you are out and about: from on land and on the water.