ESSEX REPTILES AND AMPHIBIANS. 
147 
panion ; but, one morning, I found that the vole had killed the 
viper and eaten the head and an inch or so of the body. Very 
likely lizards form a large part of vipers’ food ; and we noticed 
that the common lizard was remarkably numerous in the Forest 
in 1919. 
2.—THE GRASS SNAKE OR RING SNAKE 
(Tropidonotus natrix). 
is common in most if not all parts of Essex, and is really abun¬ 
dant at Theydon Bois. In a quarter of a mile, near the lake at 
Birch Hall, it is not unusual to see ten or a dozen snakes. They 
are, as a rule, very timid, and retreat beneath the dense thorny 
thickets, or project themselves like water voles into the lake. 
Nevertheless, we have sometimes managed to bag three or four 
in half an hour. 
In Essex, the grass snake is very fond of water. Sever?. 1 
times I have seen snakes swimming spontaneously across the 
widest part of a lake; sometimes the head and three inches 
of the body are held above the water, but at times they swim 
with the tip of the nose and the eyes only above the surface. 
It is, too, not uncommon to see snakes entirely submerged, and 
sometimes a yard deep, exploring the recesses of a pond. While 
thus engaged the reptile looks like an eel, and must frequently 
be mistaken for the fish. 
Repeated diving soon tires a snake, and if pursued in a boat 
the animal is utterly exhausted after about a dozen dives ; and 
so, too, is the rower, for the snake is extremely agile, and dodges 
about while under water. It is strange that the snake does not 
seek to escape by swimming to the cover of the bank without 
rising to the surface—a feat it is quite capable of doing, for I 
have watched snakes, when not alarmed, swimming for some 
minutes beneath the surface of a pond. 
In spite of many authors, grass snakes eat toads ; and, per¬ 
haps, these form their chief food in Essex. I have often forced 
a bulky snake to disgorge its prey, and, at Theydon Bois, a toad 
has been the result in every instance. I have never seen a grass 
snake either in the early morning or in the late afternoon or 
evening, although I had excellent opportunities for daily obser¬ 
vations at Birch Hall. 
