434 MURID^— AGRESTIS 



Status: — This mouse, like the shrew and stoat of the island, is 

 peculiar to Islay, which has evidently long been separated from the other 

 islands and the mainland of Scotland. MacGillivray's Grass Mouse is 

 slightly more primitive in pelage and skull than the other forms of M. 

 agrestis, and so may be regarded as an insular survival rather than as a 

 new development. 



THE HEBRIDEAN GRASS MOUSE. 



MICROTUS AGRESTIS EXSUL, Miller. 



1908. MiCROTUS AGRESTIS EXSUL, G. S. Miller, Ann. and Mag. Nat. Hist., 

 February, 201 ; described from North Uist, Outer Hebrides ; type specimen, 

 No. 6.3.1.3 of British Museum collection ; Trouessart ; Miller {Catalogue). 



1909. MiCROTUS AGRESTIS INSUL, R. Lydekker, Zool. Record, 1908, xlv., Mamm., 

 74 ; accidental renaming of exsul. 



History: — The occurrence of Grass Mice in the Inner Hebrides has 

 long been known, but, with those of Orkney and the mainland, they 

 have generally been lumped together as representing one widely dis- 

 tributed species. From South Uist they were first reported to Harvie- 

 Brown by M'Donald of Rodil and Henderson of Loch Boisdale, 

 and in 1879 Harvie-Brown himself captured a specimen at Newton, 

 North Uist. The relationships of the Outer Hebridean form were, 

 however, not recognised until Miller began his work for his Catalogue; 

 his description of exsul was based on fourteen examples from North and 

 South Uist, all of which except three had been taken by Kinnear, who 

 supplied the first properly prepared specimens of this form. The 

 presence of " voles " on other Scottish islands was also long known, 

 having been mentioned by Alston in 1880; but, in the absence of 

 systematic collecting, they could not be submitted to accurate study 

 until the receipt of Sheppard's specimens in 191 2. (See footnote on 

 p. 422 supra") 



Distribution : — This is the Grass Mouse of the Hebrides generally, 

 where it has thus far been found, often in abundance, on Arran 

 (common, Alston), Gigha, Jura, Mull, Skye, North and South Uist, and 

 Benbecula. In Jura it is sometimes so numerous as to be a danger 

 to young plantations (Henry Evans, in lit., nth February 1900). It 

 probably occurs also in other islands, as Rum (Millais). It is absent 

 from Lewis (Duns, 1865, 620, and later writers), but there are distinct 

 forms in Islay, Eigg, Muck, and Bute. 



Description : — This large Grass Mouse differs from the Skandinavian 

 M. a. agrestis only in the frequent presence of a small posterior fourth 

 inner angle in m^. "From the Common Grass Mouse it may be 

 distinguished by its much larger size and duller brown colour. From 

 M. a. macgillivraii it differs in its slightly brighter colour, thicker pelage, 

 and in the skull characters as already described above on p. 433. 



