snakes
A snake is a are limbless, elongated reptile that evolved from lizards. All snakes are carnivorous animals and many species produce venom which helps to kill their prey. Being reptiles, they are cold-blooded animals, lay eggs, and have scales. There are over 3,500 species of snakes. Of these, approximately 600 species are venomous.
Where are snakes found?
Besides a few exceptions, snakes are found all around the world. They found in six continents but are uncommon in the Arctic and are not found in Antarctica, Iceland or Greenland. Snakes have also never managed to colonize Ireland and New Zealand although the odd sea snake is seen in coastal waters of New Zealand. Besides this handful of places, snakes are found in all other countries/regions.
Being cold-blooded reptiles, snakes prefer warmer areas and aren’t typically found in alpine environments. They can be found in forests, in particular, tropical forests and are also common in grassland ecosystems. Snakes, along with other reptiles, are the most successful vertebrate animals in one of the Earth’s harshest environments, deserts. As well as being found on land, snakes are also very successful in water and many species spend their entire lives in the sea or share their time between the land and the water.
How old are snakes?
The evolutionary age of snakes is not very well-known because of poor fossil records. It is thought that snakes have been living on Earth for over 100 million years since the late Cretaceous period but some people believe they may have been around for as long as 300 million years.
The oldest snake fossils are found in the Middle East and South America and are both marine and land-dwelling species. Compared to other reptiles, individual snakes usually live relatively short lives. The average lifespan of a snake is around 9 years although in captivity some snakes have lived for up to 50 years. In comparison, crocodiles have an average lifespan of around 70 years and turtles an estimated lifespan of 80 years.
How do snakes move?
Despite having no limbs, snakes are very mobile and agile. They are able to move in a range of different ways for different purposes and are able to use two methods for movement at one time. Two common methods of movement are simple and lateral undulation where snakes create sideways bends in their bodies and use each bend to push-off any surface that it comes into contact with.
Other methods of movement include:
- Side-winding – similar to undulation but only a couple of sections are in contact with the surface and the raised parts of the body are pushed forward towards the advanced “in-contact” section
- Concertina – a snake pulls the body into bends and then straightens out again
- Rectilinear – a snake moves in a straight line by manipulating its underside scales to lift forward and then lower into the surface before moving backward using the friction of the scales pulls the body forwards
Venom
Many snakes, such as cobras and vipers, have evolved venom which they use to help kill prey or as a defense tool in dangerous situations. Venom is a modified saliva that contains a number of toxic compounds which have a range of effects including paralysis, digestion, blood clotting and cardiac arrest. It is usually injected during a bite through unique fangs although some species are able to spit their venom. Because there is no distinct evolutionary relationship that separates venomous snakes and non-venomous snakes it is believed that venom evolved more than once.
Last edited: 6 March 2018
