492 MURIDA:k—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, 17S.,; for a figure of a surface nest see M. S. H. Smith, Waturalist, 
1912, 7; the surface nests were also described by Oldham, WVaturalist, 1892, 4. 
Collett writes that the nests of the Norwegian A. ferrestris have two entrances. 
2 Number of young :—Adams has found five (6th May), five, three, and two; 
Pennant, six foetuses; Aflalo, seven; W. Evans (S.), seven, still blind, in nest, 
14th May 1898; Jenyns, eight foetuses in a black female, 15th June 1830 
(Observations in Nat. Hist., 1846, 76); Collett reports ten in an A. ¢errestris in a 
special “vole” year. 
3 E. R. Alston. 
* One still blind but able to swim, taken 16th June, opened its eyes on 23rd June— 
H. G. M. Williams, of. czz. 
5 Compare the Hedgehog, a primarily insectivorous, but frequently carnivorous 
mammal. 

