Reptiles and mammals share a common Carboniferous ancestor that laid eggs on land, as opposed to fishes and amphibians that laid their eggs in water. Reptile, bird, and mammal eggs have an amnion, a membrane that surrounds and protects the embryo. Although boas and pythons give birth to live young, other reptiles lay eggs, whose incubation temperature determines whether hatchlings are male or female. The hatchlings have no maternal assistance, using an egg tooth to break out of the eggshell. The earliest of modern reptiles to evolve were the turtles, tortoises, and terrapins, followed by the saurians, which gave rise to two lineages. One gave us the crocodilians, and the dinosaurs, whose descendants are the birds, and the other gave rise to the tuataras and to the skinks, lizards, snakes, iguanas, and chameleons. Currently there are about 8700 reptile species, of which 35% (just over 3000 species) are threatened, with 423 of these endangered.
Unlike amphibians, reptiles do not undergo metamorphosis and are air-breathing throughout their lives. They have a special skin made up of scales or bony plates, or both, which is shed regularly. Reptiles are cold-blooded, so their metabolic rate is dependent on the environmental temperature. They do not maintain a constant internal body temperature like birds and mammals. As they have no sweat glands or the ability to pant they cannot cool down on a very hot day other than by moving out of the sun. In very cold weather they become inactive.
There are 7 species of reptile in the UK; the Pond Terrapin (East Anglia only), Common Lizard, Sand Lizard (heathland only, rare), Adder, Barred Grass Snake, Smooth Snake (heathland only, rare), and Slow Worm. With the exception of the Pond Terrapin (a British species for 5000 years, according to the fossil record, and not a Pet Shop escapee) all are found in Sussex.
British Reptile Indentification and Location
Before one can discover reptiles one must get to know their environment, and this means spending time in their habitat to get to know its characteristics; its sights, sounds, odours, tastes, and textures, and how these change with the weather and seasons, as well as with human interference. Visit the habitat in all weathers and at all times of the year, and look, listen, smell, taste, and touch all parts of it (tasting only what is safe). When you know the habitat intimately, you will be able to detect when it has changed because of the presence of a reptile.
If you know the reptile’s lifestyle, especially when it is likely to be active (hunting, seeking a mate, courtship, escaping from a predator, etc.), you will sense its presence and why it is there. Particularly, you must look, listen and smell, and respond accordingly. Be silent, but if this is impossible then keep stopping to discern if what you have detected is reacting to your movement and its ceasing. Once you know what sensory differences are expected from a certain reptile’s presence you will begin to find it easier to track it down.
Wind, rain, sunlight, snow, ice, and other meteorological elements all affect a habitat, and you must know how and with what consequences. Similarly, you must judge how wildlife will react to weather if you want to find it. Finding a reptile that will be sheltering is very difficult because it knows the nooks and crannies better than you do. ‘Think animal’ all the time. Whatever the weather, reptiles still have to feed, and by thinking animal you can work out how and possibly where.
Reptiles generally leave few traces. They swallow their prey whole so don’t leave food remains. Being cold-blooded, reptiles are most active in warm conditions, and may be seen basking in the sun. However, in long hot, dry spells they avoid the heat and lay dormant under shade. They are generally dormant over Winter, slowing down their metabolism to conserve energy, usually hiding under vegetation. In Spring lizards are usually the earliest to become active, followed later by the snakes. Sunshine after rain is a good time to observe them; listen for rustles in vegetation as they move. All snakes and lizards slough their skin at least once a year, young ones more often, and the sloughed skin is most commonly found in the Summer. Lizards and Slowworms can lose their tails without harm, for example, when attacked, but only lizards routinely regrow them.