REPTILE AND AMPHIBIAN IDENTIFICATION
The reptile and amphibian species in the UK are fairly easily identified with a little experience. Most confusion occurs from a few common mistakes. The most common misidentifications are:
Slowworms being identified as snakes
Newts on land being identified as lizards
Confusion between frogs and toads
In addition, there are some species that are genuinely difficult to distinguish. In particular, the newts pose some problems. Male smooth newts are often identified as crested newts, though these are easily distinguished when one has some familiarity with both species. Female palmate and smooth newts are very difficult to tell apart.
Many identifications of foreign species are due to unfamiliarity with the natural variation of the native species. All of the native species exhibit some variation, and young specimens may look very different to adults.
Some of the important features for identification of the native species are outlined below.
NEWTS AND LIZARDS
Lizards are usually fast-moving, with a dry, scaly skin. The body scales are tiny and bead-like. There are large scales on the top of the head, and the whip-like tail has rings of thin scales around it.
Newts in the water have a smooth and slightly slimy skin (palmate and smooth newt), or a warty skin (crested newt). Newts on land have a dry, velvety skin (palmate and smooth newt) or a warty skin (crested newt). Newts on land are slow moving, and easily caught, unlike lizards.
THE THREE NEWTS
The crested newt is very easy to distinguish from the other two species, due to its rough warty skin. In addition, it is somewhat larger, being around 15cm long when adult, compared to the 10cm of the two smaller species. The male smooth newt is often mistaken for a crested newt, as it also has a large crest. The crest of the smooth newt is rather wavy, while that of the crested newt is more saw-toothed in appearance. Male smooth newts have a smooth skin, compared to the warty skin of the crested newt.
Male palmate newts do not have a tall crest, but have a distinct ridge along each side of the back. This ridge is evident at all times, even outside the breeding season. In the water, they usually have a thin black filament extending from the end of the tail.
Female palmate and smooth newts are very similar, and are hard to distinguish. The easiest way to distinguish newts is to check for spotting on the throat. Female palmate newts have unspotted throats, while those of the smooth newt are usually spotted to some degree. Female crested newts have a warty skin that is identical to that of the male.
Juvenile crested newts are similarly warty, and are thus easily identified. Juveniles of the two common species look very similar to adult females, but the throats of both species are often unspotted in young individuals. The belly colour of young smooth newts is usually more orange than the yellowish-buff of young palmate newts.
Larvae of the crested newt are much larger than those of the smooth and palmate newts, are more silvery, and show some black spotting. The head is wider and more 'spade-shaped'. Larvae of palmate and smooth newts are impossible to distinguish with any certainty.
FROGS AND TOADS
Frogs and toads are very easy to tell apart, as frogs have a smooth, slimy skin, where toads have a dry, rough, warty skin. Common frogs have a black 'mask' behind the eyes, which is lacking in toads.
The tadpoles of common toads and common frogs are surprisingly easy to tell apart, when well grown- frog tadpoles are coppery or brown in colour, with mottled dark markings. Toad tadpoles are a uniform dark brown or black colour.
The natterjack toad has a thin yellow stripe along its back, even in very young specimens, which distinguishes it from the common toad.
SNAKES AND SLOWWORMS
Slowworms are relatively slow moving, even when disturbed, and they move rather stiffly. They have a glossy body, often with a metallic sheen.
Snakes are much faster moving than slowworms, and move in a smoother manner. The two common species in the UK, the grass snake and adder, both have a matt appearance, very unlike the shiny appearance of a slow worm.
Slowworms are occasionally thought to be adders, perhaps due to the stripe along the back. The stripe on a slowworm is a fine straight line, unlike the wide rough-edged or zigzag stripe alone the back of an adder. Adders usually have a V- or X- shaped marking on the back of the head, while slowworms usually have uniformly coloured heads.
Some books will state that the presence of eyelids in the slowworm is a useful diagnostic character. This is of little use in the field, as it is almost impossible to get close enough to see this without capturing the animal, and capturing an unidentified legless reptile is not advisable.
Grass snakes and adders are very easy to tell apart. The yellow collar on a grass snake is a giveaway. Although old specimens may have a duller yellow collar, the black crescent behind it will still be present. The grass snake is much longer and more slender than the adder, and has a green or olive ground colour. There is no continuous stripe along the back as in the adder.
LIZARDS
Any animal in the classic lizard shape, once it has been established it is not a newt, is most likely to be a common lizard. Sand lizards will only be encountered in Surrey, Hampshire and Dorset, or on the coastal sand dunes of Merseyside. Sand lizards have distinctive ocelli on their sides- black rings with a lighter centre. Males are also often very green on the sides, unlike the brownish colour of common lizards. Young common lizards may have small ocelli on their sides when very young, but their blue-black colouration is very unlike the brown colouration of young sand lizards.
ALIEN SPECIES
It is very unlikely that an alien species will be met with in the UK. Most of the alien species are relatively easy to distinguish.
The two most numerous introduced species are the marsh frog (Rana ridibunda) and the midwife toad (Alytes obstetricans).
The marsh frog is found over a large area of Kent and East Sussex, and is very unlike the common frog. It is much larger (up to 15cm), is greenish or olive in colouration, and has a distinctive call, which will be very evident around any established colony throughout the summer.
The midwife toad is similar to a small common toad, but its eye has a thin, cat-like vertical pupil, compared to the horizontal rounded pupil of the common toad. Males carrying eggs are instantly recognisable. This species is most likely to be found near the established colonies around Bedford and Worksop.
The two most widespread species are probably the red-eared terrapin (Pseudemys scripta elegans) and the american bullfrog (Rana catesbeiana). These species, though not as numerous as the marsh frog or the midwife toad, have been released into a larger number of places.
Any terrapin is recognisable as an alien species, as no chelonians occur naturally in the UK. The red-eared terrapin usually has a red marking on each side of the neck.