Slow worms and greater white-toothed shrews sharing refuges

Abstract

T slow worm Anguis fragilis is a legless anguid lizard native to Britain. There is also a colony in the Burren area of the west of Ireland, in counties Clare and Galway, where it is presumed to have been introduced. I have studied this colony since 2015 and to this end have employed the use of artificial cover objects (ACOs) of various materials including roofing felt, hardboard, and corrugated iron. The refuges had an area of about 0.05 m2 and were positioned close to various thick vegetation and bushes that provided good cover for slow worms. The presence of the greater white-toothed shrew Croidura russula was first discovered in Ireland in 2007 in pellets of birds of prey (Tosh et al., 2008) in Counties Tipperary and Limerick. It is thought to have originated from France and is believed to be spreading at a rate of 5 km per annum. It was on 16 June 2022, while completing my regular survey of ACOs, that I discovered the two species sharing the same refuge, in this instance a piece of corrugated iron placed on a roadside verge in the townland of Dereenatloghtan in County Clare. Upon lifting the refuge, a pair of white-toothed shrews were observed along with a male slow worm. One of the shrews immediately departed leaving just a single shrew and the slow worm (Fig. 1). While the slow worm was not disturbed by my frequent visits it appears the greater whitetoothed shrews were, as they were not observed there again. These shrews have increasingly been noted under a number of refuges at different sites, but this was the only occasion when a photograph was possible of the two species together. Shrews are insectivores whose diet is not confined to insects and it has been noted that young slow worms are at risk of predation by shrews (Simms, 1970; Beebee & Griffiths, 2000). In the case of white-toothed shrews, a study in Algeria showed that of 115 items in the stomach contents of 15 shrews, a total of three (1.9 %) were lizards/ geckos which accounted for 14.9 % of prey biomass (Brahmi et al., 2012). I have not observed slow worm predation by the white-toothed shrew but this very probably happens. The same is likely to be true for Ireland’s only native reptile, the viviparous lizard Zootoca vivipara, which may be even more vulnerable as it lacks the protective osteoderms that are present as a ‘chain-mail’ protection in the skin of slow worms (Beebee & Griffiths, 2000).