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Of all the mammals you are likely to see in Northern Ireland the one most likely to give you a real thrill is the playful otter, often appearing to take childlike enjoyment in sliding around muddy banks or, less innocently, trifling with cornered prey. Known for its shyness and its ability to keep out of sight, an encounter with an otter is a rare treat.
The otter is a member of the Mustelid family, a group of carnivorous mammals which includes stoats, badgers and pine martens. The otter is the largest Mustelid with average males measuring 120cm from nose to tip of tail and weighing 11kg, while females are generally smaller, weighing around 7kg. Recognisable characteristic features of the otter include a streamlined dusky brown body and a thick tapering tail. At a glance, otter and mink can appear quite similar; though the table below should help you tell them apart.
| Otter | Mink |
| Size | Larger than largest cat | Smaller than an average cat |
| Colour | Mid brown when dry, darker when wet. Paler throat and chest. | Usually dark brown to almost black, sometimes with a white chin patch |
| Head shape | Broad muzzle | Pointed face |
| In water | Swims smoothly with only top part of head visible above the water. Leaves a distinctive V shaped wake. | Swims jerkily with head, shoulders and top of back out of the water. |
| Communication | Not very vocal.Leaves spraints (faeces) on prominent spots along river. | Alarm shriek and mating purr, also communicates via spraints. |
The otter’s principal food source is fish and occasionally other vertebrates such as water birds, rats and even rabbits. Invertebrates such as crayfish, crabs, worms and insects may be taken in quantity when available. Otters are found in a wide variety of locations throughout Northern Ireland; both coastal and freshwater. It is believed that Ireland now holds the densest population of otters in Western Europe, although it is estimated that in the last 20 years otter abundance in Northern Ireland has dropped by 10%. Otter protection
The otter is listed on Appendix 1 of CITES (Convention on International Trade in Endangered Species), Appendix II of the Bern Convention and Annexes II and IV of the Habitats Directive. It is also protected under Schedule 5 of the Wildlife (NI) Order 1985. However in Northern Ireland, as recently as April 2008, it has been acknowledged that otters are still being trapped and killed in local rivers. Main Threats to Otters
Habitat loss, for example by riverside development, intensive use of farmland adjacent to rivers and engineering works to banks/ channels.
Inadequate food supply due to loss of principal fish prey (often linked with high nutrient loads and de-oxygenation of the water body).
Poisoning from pesticides, heavy metals or other toxins that persist in the food chain.
Disturbance of breeding sites.
Road traffic.
Accidental drowning in fishing nets.
The Northern Ireland Environment Agency (NIEA) is hoping to reduce one of the above threats, accidental drowning in fishing nets, by offering free otter guards to eel fishermen. Anyone wishing to obtain one should contact the NIEA Wildlife Officer on 028 9025 1477. What we can do to help otter populations
- Farmers can fence off buffer strips, the wider the better, along river corridors, to allow natural bank-side vegetation to persist and safe passage for otters. Grant aid through agri-environment schemes may be available towards the cost of fencing.
- Resist the urge to ‘tidy’ or undertake formal landscaping along a riverbank – leave as much natural vegetation as possible, allow log piles or dead timber to rot down naturally and ensure there is some tall vegetation for concealment.
- Create an artificial otter holt - click here for details.
- Keep septic tanks in good condition to protect waterways from pollution caused by waste run-off.
- Eel fishermen can fit otter guards to their nets (see above).
- Developers should refer to CIRIA guidelines which offer best practice advice for mitigation including provision of otter passes, designing otter-friendly culverts, maintenance of habitat corridors etc.
- Report sightings of otters to the Centre for Environmental Data and Recording (CEDaR) by email on cedar.info@nmni.com or by telephone on 028 9039 5256.
- Report incidents of disturbance to otters or their holts to the Wildlife Officer at NIEA (contact above), including incidents of otters drowning in nets or illegal cage traps.
Useful links
View the NI Otter Species Action Plan here.
