Reptiles in the Garden
Like the amphibians, reptiles are cold-blooded; that is, they do not maintain a constant body temperature but take on that of their surroundings. They are most active in warm weather and become increasingly lethargic as the temperature drops, until, in cold weather, they become completely torpid. They are able to hibernate through long winters, the viper or adder being found nearly as far north as the Arctic Circle. There are no snakes in Ireland.
The reptiles to be found in Great Britain are three species of snake—the grass snake, the adder and the smooth snake; two lizards—the common and the sand lizard; and the slow worm— which looks like a snake but is really a legless lizard.
Young reptiles hatch out from eggs which are not incubated by the parent. The fertilized eggs of the adder, smooth snake, common lizard and slow worm are retained within the body of the female until they are just about to hatch, and the young are therefore born alive. The eggs of the other hatched by the heat of the sun and the warmth generated by decaying vegetation. For this reason a compost heap is sometimes a special source of attraction. Most reptiles prefer fairly dry conditions and are often associated with heathland. The grass snake, which is fairly catholic in its choice of habitat, is the species most likely to be found, but none of the reptiles is common in gardens, and the smooth snake is very rare, being confined to a few areas in southern England.
The snakes of the British Isles live on a variety of food including small rodents, frogs, toads, newts, lizards, insects and occasionally small birds. They like good ground cover but on sunny days may bask in exposed places.
The grass snake is long and tapering, the females (which are bigger than the males) frequently reaching 4 ft. and occasionally 5 ft. It has black spots along its back and bars along its sides, and normally there are two distinctive yellow patches placed symmetrically just behind the head though these may be missing in old females. It is an excellent swimmer and in summer may spend much time hunting in the water.
The adder is much shorter and thickset, with a rather short, blunt tail, a broad flat head, and a very distinctive dark zigzag line down the centre of its back. It is the only poisonous snake in Great Britain, its bite being fatal to dogs and occasionally to human beings. Fortunately, it very rarely attacks unless provoked.
These small reptiles move with great rapidity, especially in warm weather, and can climb rocks and walls with ease. Unlike snakes, they have eyelids.
The common lizard is 5 or 6 in. long and is the only species likely to visit the garden. The underparts of the male are orange or red, dotted with black; the female is paler, with grey spots or is even unmarked. It feeds mainly on insects, caterpillars and spiders, and is most likely to be found on hedge banks, dry stone walls and in rock gardens.
The larger sand lizard, 8 in. long, is rare, being confined to sandy parts of Surrey, Hampshire, Dorset and the coast of Lancashire. It is purple-brown with broken bands of a darker tint, but the colour is very variable and the males tend to have a green diffusion. There are rows of dark and white spots along the back flanks and tail. Its food is much the same as that of the common lizard.
The slow worm, also known as the blind worm, is bronze in colour, slender, and is seldom more than 15 in. long. Like other lizards it has eyelids. It feeds on slugs, insects and worms and spends much of its time hiding away under large stones (the rocks in rock gardens attract it), fallen trees, sheets of corrugated iron and so on. If it is trapped by its tail the slow worm will readily shed it, later growing a new, but blunter one.