THE WATER RAT 487 
Water Rats may be regarded as large Grass Mice which 
have adapted themselves to a predominantly aquatic life, but 
without specialising so far as to lose the power of resuming a 
terrestrial existence. Their love of water is shown in their 
comparatively long tail, used no doubt for steering purposes ; 
thicker, more beaver-like coat; well developed aural valves ; 
reduction in size and number of foot-pads ; and slightly fringed 
feet. In other respects they have not been specially modified 
in any really important detail for amphibian existence; but 
their life by ponds and watercourses has led them to construct 
a somewhat peculiar type of burrow, and they show a preference 
for certain water-loving herbs, which are not usually in the 
path of the ordinary Grass Mice. 
Our own Water Rat, although a comparatively large 
animal and hunted by many predatory creatures, to which it is 
extremely palatable, manages to exist in numbers in a region 
wherein all other members of its sub-family, except the smallest, 
have been exterminated. Several large voles allied to or 
identical with the Skomer Bank Mouse, the Northern and 
Orkney Grass Mice and the Snow Mice,’ flourished in south 
Britain in the late Pleistocene period, but now exist only in 
the sanctuaries afforded by islands or mountainous regions. 
The Water Rat alone remains, partly no doubt because it has 
no direct competitors amongst the members of its own sub- 
family and partly because it has adopted the happy expedient 
of relying on water for a retreat from its enemies. By doing 
so it incurs the risk of being snapped up by herons,’ pikes, 
large eels,*® and trout, and it is a staple food of owls, stoats, 
polecats and, perhaps, foxes; but it avoids many of the other 
enemies of its tribe. Like all water dwellers in cold or temperate 
countries it suffers from inundations which drive it from its 
burrows ; from frost, a combination of these two being most 
inconvenient ; or droughts ; but on such occasions it is always at 
least as much at home on dry land as would be a Grass Mouse 
1 Chionomys, see p. 470. 
2 J. G. Millais has seen a heron kill a small one, and T. A. Coward and Charles 
Oldham find the pellets thrown up by herons (Cheshire, 55) consisting almost entirely 
of the fur of Water Rats. 
3 Nat. Hist. Trans. Northumberland and Durham, v., 1877, 341; for an eel 
seizing a Water Rat’s tail, see J. D. Patchett, /ze/d, 12th September 1891, 431. 
