The Yellow anaconda is a non-venomous boa species endemic to southern South America. It is one of the largest snakes in the world but smaller than its close relative, the Green anaconda. The color pattern consists of a yellow, golden-tan or greenish-yellow ground color overlaid with a series of black or dark brown saddles, blotches, spots, and streaks. Females in this species are generally larger than males.
The range of the Yellow anaconda encompasses the drainage of the Paraguay River and its tributaries, from the Pantanal region in Bolivia, Paraguay, and western Brazil to northeastern Argentina, and possibly parts of Uruguay. These snakes prefer mostly aquatic habitats, including swamps, marshes, and brush-covered banks of slow-moving rivers and streams.
Yellow anacondas are solitary snakes that can be active both during the day and night. They spend most of their life in or around water and are sometimes known as "Water boas”. When in water anacondas usually float atop the water, with their snouts barely poking out above the surface. Although most of their time is spent in aquatic habitats, Yellow anacondas do come out onto land in order to move to other water bodies, for hunting terrestrial prey and for mating. They forage predominately in shallow water in wetland habitats using ambush predation and wide-foraging strategies. Most predation occurs from June to November when flooding has somewhat subsided and wading birds are the most common prey. These snakes are considered timid and usually try to escape from predators, however, if threatened they will defend themselves.
Yellow anacondas are carnivores. Their prey consists nearly exclusively of aquatic or semi-aquatic species, including a wide variety of mammals, birds, reptiles, amphibians, fish, and eggs. Larger specimens can prey upon larger animals, such as Brocket deer, capybaras or peccaries.
Little is known about the mating system in Yellow anacondas. They are ovoviviparous and give birth to live young. These snakes usually breed between April and May. During this time females produce pheromones which attract the males. The courtship usually takes place in water. Yellow anacondas may form breeding balls, consisting of one female and multiple males, which may stay together for up to a month. The males compete for the female, and the strongest and largest male will breed with the females. Females give birth to 4-82 young after the gestation period that lasts around 6 months. After giving birth, the mother leaves her young and they are able to live on their own. Yellow anacondas become reproductively maturity when they are 3-4 years old.
There are no major threats for Yellow anacondas at present. However, these snakes are hunted for their skin and used in the pet trade. They also suffer from the destruction of their habitat.
Yellow anacondas are one of the top predators in the ecosystems they inhabit. They feed upon a wide variety of vertebrate animals thus controlling their populations.