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Saturday, 7 May 2016

New shrew invader on its way to Kerry

A new species of mammal is on its way to Kerry and the implications for native raptors and small mammal species is likely to be profound.

Greater White-toothed Shrew (Rasback Wikimedia Commons).

Greater White-toothed Shrews were discovered in Tipperary in 2011 and are spreading at an average rate of 5.5km per year, more than twice that of the Bank Vole. The western edge of their range is now only about 30-35km from the Kerry border, which will mean they will arrive in the Kingdom in as little as six years. 

This is also assuming there isn't a 'jump' in the range. The map below shows two established outlying populations of the shrew, one in Monaghan and another to the NW of Cork City. These were most likely from small numbers of shrew transported accidentally from the core range in Tipperary. This could happen again anywhere in Ireland and in any case, it has been estimated that the invader will spread to the whole island of Ireland by 2050. Like it or not, it is here to stay.

Range expansion of Greater White-toothed Shrews in Ireland, to 2013. There are two outlying established populations in Monaghan and Cork city, though a third, to the west of Limerick, and only 15km from the Kerry border, died out shortly after its discovery in 2010  (McDavitt, et al, 2014)
You can click the map above for closer look.

Pygmy Shrews have been disappearing wherever the White-toothed Shrew invades, and numbers of Wood Mouse have been decreasing. Raptors are feeding voraciously on the new mammal and though it was thought that it might have a positive effect on raptors, offering an abundant new food source, there have been issues with e.g. sickly and underweight Barn Owl chicks which are fed on a diet of these new mammals. The full effects of the invader are as yet unknown, but it is on its way, and here to stay, whether for good or bad.

See more on this on the Irish Raptor blog HERE.

Citation: McDevitt AD, Montgomery WI, Tosh DG, Lusby J, Reid N, White TA, et al. (2014) Invading and Expanding: Range Dynamics and Ecological Consequences of the Greater White-Toothed Shrew (Crocidura russula) Invasion in Ireland.