Reptiles The amniotic egg was an evolutionary conquest of the reptiles that allowed them to become independent of water bodies for reproduction; unlike amphibians, they do not have an aquatic life phase. In Portugal there are representatives of only two reptile orders: Testudines (turtles and tortoises) and Squamata (geckoes, lizards and snakes). Similar to the amphibians, reptiles are ectothermic, ie they depend on external sources of heat (e.g. sunlight) to regulate their body temperature. For this reason, they are often observed sunbathing next to trails or roads or on rocks or walls. They can stand high temperatures and low humidity and, for most species, water ingested through food is sufficient to keep them hydrated. Reptiles suffer from ignorance and prejudice, and are often killed by humans. In Portugal, only two species (the vipers) are potentially dangerous to humans and they only attack if provoked. Reptiles play very important roles in ecosystems, preying on a wide range of invertebrates and vertebrates whilst also being the prey of other reptiles, birds and mammals. Other threats to these animals are habitat loss and road development, and a lot of individuals are killed by road vehicles.