4. Snakes
The roughly 3,500 species of snakes are really a group of limbless lizards, although they are so distinctive, with so many unique features, that they are placed in their own reptile subclass, Ophidia or Serpentes. They have a worldwide distribution, occupying habitats from deserts to rainforests and seas. ‘Snakes’ describes how snakes feed, move, and make sense of their surroundings, as well as their social and reproductive behaviour. The main aspect of snake biology that accounts for their great success as hunting organisms is the way they acquire and ingest their food. The rear-fanged (colubrids) and front-fanged groups (elapids and viperids) are described along with their venom production.