492 MURID^— ARVICOLA 



which may be at varying distances from the entrance, and at 

 no time do the passages lead much below the surface of the 

 ground, the type of excavation thus somewhat resembling that 

 of Bank Mice. 



The burrows rarely show any traces of occupation such as 

 food, droppings (which are usually deposited by the water), nests, 

 or nurseries. When the latter are present a ventilation hole may 

 be provided, but where there are reed-beds or other herbage, 

 they are quite frequently placed on the ground exactly like 

 those of Grass Mice, and occasionally in hollow willow trees. 

 In size and composition they resemble those of waterhens, the 

 material used — reeds and grass — not being invariably shredded,^ 

 as is always the case with Grass Mice, 



For breeding purposes the Water Rat prefers tributary 

 streams and backwaters to main rivers. To these it retires in 

 pairs early in spring, and the young, which sometimes number 

 as many as eight, ^ may be seen on the banks throughout the 

 summer, occasionally in April, ^ but more usually from May 

 until autumn, so that several litters are probably reared by each 

 couple. The male probably remains with his mate throughout 

 the sexual season and does not harm his young ; they probably 

 grow at about the same rate as Grass Mice.* 



The Water Rat, although without doubt predominantly a 

 vegetable feeder, has, like others of its family, no objection to 

 an omnivorous diet. The extent to which such wider tastes 

 are indulged is, as in other similar cases,^ very variable, 

 depending probably on a number of predisposing factors. In 

 eating, it usually sits up like a squirrel, holding the food in 

 its hands, and where the favoured diet consists of roots or 



1 Adams, MS.y for a figure of a surface nest see M. S. H. Smith, Naturalist, 

 1912, 7 ; the surface nests were also described by Oldham, Naturalist, 1892, 4. 

 CoUett writes that the nests of the Norwegian A. terrestris have two entrances. 



2 Number of young :— Adams has found five (6th May), five, three, and two ; 

 Pennant, six foetuses ; Aflalo, seven ; W. Evans i^MS.), seven, still bhnd, in nest, 

 14th May 1898; Jenyns, eight fcetuses in a black female, 15th June 1830 

 {Observations in Nat. Hist., 1846, 76) ; CoUett reports ten in an A. terrestris in a 

 special " vole " year. 



3 E. R. Alston. 



'' One still blind but able to swim, taken i6th June, opened its eyes on 23rd June— 

 H. G. M. Williams, op. cit. 



8 Compare the Hedgehog, a primarily insectivorous, but frequently carnivorous 

 mammal. 



