Species Otter

The otter's dense fur provides insulation, while their muscular tail and webbed feet make them excellent swimmers. Their eyes are positioned high on the head, allowing for better vision while swimming. Otters have a broad snout and small ears and their sensitive whiskers and sharp claws help them detect and catch prey in aquatic environments. On average, males are larger than females.

Much of what is known about their distribution, habitat use, and diet comes from identifying tracks and other signs. One of the most distinctive markers of otter activity is their droppings, known as spraints, which they use to mark territorial boundaries. These are often found on in-stream boulders, bridge footings, and grass tussocks.

Otters are highly territorial, with territory sizes varying depending on food availability. Coastal territories can be as small as 2km, while those along upland streams may extend up to 20 km. Males typically have larger territories than females, often overlapping with multiple female territories. 

Within their territories, an individual otter may use several holts. These tend to be natural crevices associated with the roots of trees growing along river and lake banks. A holt usually has multiple entrances from which the otter can escape if disturbed. Otters rarely dig their own holts and use burrows from other animals, such as rabbits and foxes. 

Frogs are a frequent dietary component, and analysis of spraints has revealed remains of invertebrates, including crayfish, as well as birds and small mammals.

Otters living in rivers and lakes tend to be completely nocturnal, with activity peaks at dusk and dawn. Foraging at night or in ‘muddy’ water is helped by their highly sensitive whiskers, which detect their prey items. Otters that forage at the coast may have flexible foraging times linked to the tides. At low tide, otters hunt in the exposed rock pools and seaweed-covered rocks for fish and invertebrates.

Female otters use scent markings to signal they are ready to mate, attracting potential males. Gestation lasts approximately two months, after which a litter of two to three cubs is typically born, though litters of up to five have been recorded.

The cubs remain in the natal holt for up to two months before venturing out on their own, although the mother may move the cubs between holts within her territory. Unlike other resting sites, the natal holts do not tend to be marked with spraints. 

Juvenile otters remain with their mother as a family group for six months or longer before they disperse to establish their territories.

Maintaining prey populations and preserving the natural features of rivers, lakes, and coasts will benefit the Irish otter population and ensure that it remains a European stronghold.