Analysis: otters are attracted to cities for their rivers, which are rich with such prey as fish, eels and water birds

Across Europe, the number of otters declined in the last century. In Ireland, they are still common, but rarely seen. In Irish cities, oddly, they are common. The cities are all on rivers, mostly estuaries, which is one of the best otter habitats, being rich with such prey as fish, eels and water birds.

Ireland's urban otters are distinct from otters found elsewhere. They have darker coats and are very sexually distinct: the males are much bigger than females and, with practice, the sexes are readily told apart. Males tend to occupy the main river, and the females the smaller tributaries. In effect, females avoid the males.

Usually, top predators such as otters are scare in urban areas. Where predators exist, they are indicators of a functioning ecosystem even if a slightly odd and unexpected one. Apart from indicating intact biodiversity, the other good news for conservation is that people who live in urban areas are more likely to be concerned with the decline in biodiversity, as they see less, which makes urban areas good recruiting grounds for conservationists. Otters are a useful subject for studies to connect people to conservation of their local small river.

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From RTÉ lyric fm's Naturefile, a look at the otter, one of Ireland's most charismatic native mammal species

Dublin is a city of rivers and one of these is the River Owendoher, which is an English version of the Irish Abhainn an Dobhair or river of the otter. It is well used by otters to this day because its steep sides make access for people and their dogs difficult. Otters like being away from local human disturbance.

I participated in a survey of otters in Dublin in October 2018. I recall hearing the rumble of trains in Heuston Station, while walking along the River Camac from Kilmanham. It felt like changing from being a hunter to being hunted, with the chill of fear.

Finding otters in urban areas like Cork is like discovering a jewel in mud

While common in Dublin and Limerick, otters have been most studied in Cork. There 11 known otters in Cork City, identified by DNA extracted from spraints (otters’ droppings). Of these, eight use the river in the Blackpool area, making the area important.

Volunteers searched the banks of the river at Blackpool to record signs of otters. This meant wading into a cold, often rapid flowing, river, in all weathers. Over the course of a year, the core habitat at Blackpool was searched each season for three days and each spraint or other otter sign, photographed and uploaded. Astonishingly, there was fresh spraint found in all seasons, but the majority were found in summer. They are mainly nocturnal and the best time to see them is at dawn or dusk.

Blackpool is important as there are threats to cover over the river and turn it into what would effectively be a large drain devoid of most 'normal’ freshwater life. This is planned as a flood mitigation measure.

Why is Blackpool so well used by otters? Firstly, there are lots of fish, but also water birds. There are also underpasses for them which appears to save them from being killed on the roads there. The district around UCC where the River Lee splits in two is also well used by otters. Like in Dublin, areas that humans find difficult to access are where most otter activity is focused.

Finding otters in urban areas like Cork is like discovering a jewel in mud. With a little training, they can be detected via their spraints. Better still, you can set up camera traps to take a photograph of the pooper. Detecting otters in urban Ireland is the equivalent of seeing dolphins cavort on an Atlantic horizon or wild animals migrate across the plains of East Africa. This self-initiated conservation initiative connects individuals with biodiversity rich habitats, such as small rivers, in their own back-yard. But be careful as camera traps can be stolen. The fact that otters tend to use places where people do not venture helps.

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From RTÉ Radio 1's Mooney Goes Wild, Donal Glackin joins the Irish Wildlife Trust as they conduct a survey of otters in Galway city

There is a belief that otters indicate clean water; for example, their return to parts of England is said to show that water-ways have been ‘cleaned up’. But this does not stand up to close examination. Otters commonly used Cork’s waterways where 59 million litres of raw sewage was put into the River Lee every year before the mains-drainage scheme. What determines where otters can be found is prey (especially fish) rather than clean water.

Are Cork’s otters coming in from the surrounding areas or are they ‘local’? Family groups of otters including cubs have been seen, suggesting that there are otters reared within the city. This suggests there are individuals that specialise in this habitat. Pana is Cork slag for Patrick Street which curves around following the river which is without doubt used by otters, so we now have Pana otters.


The views expressed here are those of the author and do not represent or reflect the views of RTÉ