Reptiles: Ancient Lineage, Vital Roles, and Local Challenge
What are the defining characteristics of reptiles?
Reptiles are a class of vertebrates (animals with backbones) that are typically cold-blooded (ectothermic), meaning they rely on external heat sources to regulate their body temperature. They are covered in dry, scaly skin made of keratin, which provides protection and helps prevent water loss. Most reptiles reproduce by laying amniotic eggs with protective membranes, allowing for development on land. All reptiles breathe using lungs, and while some, like snakes, are limbless, the class is generally characterised by having four limbs or being descended from four-limbed ancestors.
There are four main living orders of reptiles.
- Squamata is the largest order, encompassing lizards and snakes, known for their diverse forms and behaviours.
- Testudines includes turtles and tortoises, distinguished by their protective bony shells.
- Crocodylia consists of crocodiles, alligators, caimans, and gharials, which are large, semi-aquatic predators with an ancient lineage.
- Rhynchocephalia contains only the two species of tuataras, found exclusively in New Zealand and often referred to as "living fossils."
Globally, there is immense diversity among reptiles, with over 10,000 recognised species found in nearly every continent and a wide range of habitats, from deserts and forests to wetlands and oceans. This global adaptability is significant. In stark contrast, Britain has a very limited native reptile fauna due to its climate. There are only six native reptile species in Britain: three snakes and three lizards.
Of the six native British reptile species, four have been recorded in the Sidmouth area. These are:
- Adder (Vipera berus)
- Grass Snake (Natrix natrix)
- Common Lizard (Lacerta vivipara)
- Slow Worm (Anguis fragilis)
Sources indicate that the sandy soils of heathland in the Sid Valley are a vital habitat for reptiles. Lowland dry heath habitats in Britain can potentially support all six native British reptile species. Brownfield sites are also mentioned as being ideal habitats for several reptile species. Within the Sidmouth area specifically, warm stones in places like the lower section of Sidmouth Cemetery provide refuge for lizards and slow worms, and slow worms are also found in and around town, particularly in compost heaps and under objects.
While four native British species have been recorded in the Sidmouth area (Adder, Grass Snake, Common Lizard, and Slow Worm), none of these species are considered common in the area according to the provided information. Notably, only the slow-worm has been observed during Sidmouth Nature surveying activities, and this was a deceased individual, suggesting low encounter rates for live individuals.
Reptiles play crucial roles in ecosystems as both predators and prey, forming vital links in food chains and helping to maintain ecological balance. As predators, they regulate populations of other species, preventing any one from becoming overly dominant. As prey, they are a food source for various other animals. Some reptiles also act as ecosystem engineers, for example, crocodiles maintaining waterholes or turtles influencing aquatic vegetation and nutrient cycles. Their presence contributes to the health and functioning of diverse habitats.
Reptile populations face numerous significant threats, primarily driven by human activities. These include habitat loss and fragmentation from development, pollution from various sources, climate change impacting their behaviour and distribution, overexploitation through illegal trade and hunting, and the impact of invasive species. Conserving reptiles is essential because their decline can disrupt food webs and ecosystem balance. They also represent millions of years of unique evolution and are an important part of global biodiversity. Protecting them recognises their intrinsic value and the interconnectedness of all life.