The Native Irish Pygmy Shrew Could Soon Be No More


The Irish pygmy shrew is getting beaten out of Ireland by an invader. It’s Game of Thrones time for our native shrews.

An invading species of shrew, first discovered in Ireland in 2007, is spreading across the landscape at a rate of more than five kilometres a year. And it is seriously affecting the livelihoods of our own native pygmy shrew, according to findings published in the scientific journal PLOS ONE.  If this was Game of Thrones, our own shrews would have lost most of Westeros.


This is our little native guy, a pygmy shrew. Pic: Ruth Carden

University College Dublin scientists who conducted the study say that the invading species, the greater white-toothed shrew (Crocidura russula) is capable of colonising the entire island by 2050. This, they say, is leading to the disappearance of the pygmy shrew (Sorex minutus) from Ireland, one of the world’s smallest mammals, which has been on the island for thousands of years. And seriously people this is also our cutest animal.

“The invading population of the greater white-toothed shrew currently covers an area of 7,600 km2 and is found in Tipperary, Limerick, Cork, Waterford, Kilkenny, Offaly and Laois,” says Dr Allan McDevitt, UCD School of Biology and Environmental Science. “Small satellite populations have also been found in Cork city and more recently in Mullingar, but according to our data they have not yet crossed the Shannon. Species can live together after invasions occur, but in this case there may not be sufficient landscape complexity in Ireland to allow niche partitioning between these two species of shrew.”

Says co-author Dr Jon Yearsley, “The displacement of the pygmy shrew will continue in Ireland as the greater white-toothed shrew carries on spreading rapidly, with the invader only being temporarily hindered by rivers and other barriers. Our findings suggest that at the present expansion rate, the greater white-toothed shrew is capable of colonising the whole island of Ireland by 2050. The sheer speed of the invasion of the greater white-toothed shrew and its competitive superiority in eating large insect prey could have severe negative impacts on the population of Irish pygmy shrews, and even lead to its local extinction.”


This is the enemy at large, the greater white-toothed shrew. OFF WITH HIS HEAD! Pic: Ruth Carden

Says Dr Allan McDevitt, “The greater white-toothed shrew needs to be recognised as an invasive species that has the potential to have a large negative impact on the Irish ecosystem. With these findings, we appeal to the appropriate authorities in both the Republic of Ireland and Northern Ireland to address the issue of invasive species causing severe ecological impacts across the island.”

According to Professor Ian Montgomery of Queen’s University Belfast, ensuring bigger hedgerows and more deciduous woodland may enable the protection of species against invaders.

The pygmy shrew is one of the world’s smallest mammals. Adults weigh between 3g and 6g. They have iron deposits at the tip of their teeth which give them a red colour. They have brownish hair on their upper surface and whitish grey on the belly. Their tails are thick, hairy and long relative to its body size.

The greater white-toothed shrew can weigh between 8g and 14g, or about three times the size of the pygmy shrew. As their name suggests, they have distinctive white teeth. They are bicoloured, with greyish brown hair on upper surface and yellowish grey lower belly. They have prominent ears and long, white hairs on their tail. And they are in no way as cute as our pygmy shrew.

The greater white-toothed shrews are coming. This is a battle for survival.


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