A member of the Boidae (a family of 36 species of typically large, non-venomous snakes, that rely on strength and speed to trap and kill its prey) the Green Anaconda, or Eunectes murinus is one of the largest snakes in the world, found in the hot Amazon Rainforests in South America. Just shorter than its cousin, the python, the reptilian is twice as heavy, with a large girth - when researchers and hunters find one, it often takes many people to carry them! Growing often to more than 29 feet and weighing in at 227 kilos, moving into places of shade like other snakes do is very cumbersome. So how do anacondas do it?
Anacondas have special sensory organs which are located between their scales, called labial pits. These organs are what differentiates Boas from other snakes, such as Viperines, which lack pit organs. These heat-sensitive organs are found around their mouths, and help the creature to find prey and other predators it competes against, such as the jaguar. The organ detects minute temperature changes in the form of infrared rays. When a snake is too cold, it basks in the sunlight, as otherwise its movement will become sluggish, which is unwanted when its prey are fast creatures, like deer and capybara (the world's largest rodent - they weigh in at 80kg!). If there isn't sunlight available, which is likely later in the day under the rainforest canopies, the snake can also coil up to conserve and maintain its body temperature.
In addition to this, whilst the majority of boas are terrestrial or arboreal (such as Boa Constrictors, which are semi-arboreal, using trees to stalk its prey) the anaconda is semi-aquatic. As there are many slow moving streams in the Amazon which join onto the Amazon River, this provides the animal with many places to cool down. Its nostrils are found at the top of its head to ensure they aren't submerged, allowing it to stay under the water for extended periods of time.