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A yarara, scientifically named Bothrops jararaca, is a medium-sized venomous species of pit viper. A mature yarara is fairly slender and measures about 32-63 inches (80-160 cm) in length, with the female usually somewhat longer than the male. In appearance, individual snakes of this species can differ significantly from each other because of the variety of skin tones that these snakes can have. Skin colors come in shades of olive, maroon, yellow, tan, brown or gray. Yararas do share certain physical characteristics, such as dark blotches that come in a variety of shapes and sizes on their backs and pronounced dark-brown stripes on the head that run in an angle from the mouth to just behind the eyes.
Geographically, the yarara has a limited distribution. This snake is found only in the southeastern region of South America, roughly from northern Argentina, through Paraguay to southern Brazil. Yararas are also found on a few islands that are about 20 miles (35 km) off the coast of Brazil. The yarara is regarded as the most poisonous snake within the area it inhabits. It is abundant, and many of the areas it inhabits are densely populated, so it is the leading cause of snakebite in the region.
For habitat, the yarara prefers to live in open areas where vegetation cover is near. Most often, it is found at low to medium elevations from about sea level to about 3,280 feet (1,000 m). Within its range, the yarara has adapted to a variety of habitats and is found not only in open areas but also in large cities, cultivated fields, scrubs and various types of forests.
The diet of this snake changes as it matures. When newly born, a yarara mainly preys on frogs but will also eat insects such as centipedes, lizards, birds and some small rodents. An adult snake of this species, however, gets more than 80 percent of its food from rodents. Yararas hunt at night and bite the prey to inject venom before eating it.
Breeding season ends in February and March when births occur. Its eggs are not laid in a nest but grow inside of the mother, where they also hatch so that the babies are actually born alive. Scientists estimate that the size of litters varies from about five to 22. The tail tips of newborns are white or yellowish. As the diet of the newborn changes to consuming warm-blooded animals, the tail tip darkens and takes on the colors of the rest of its body.