It took the firefighters nearly two hours to remove the snake from the backyard of the house on the edge of the city's Tijuca forest, said Sub-Lt. Armando Viana of the Rio de Janeiro fire department.
Viana said he believed the snake had entered the yard after fighting with a porcupine because it had large black spines in its head. Firefighters removed the spines and treated the snake's wounds.
Viana said another smaller boa constrictor had also been found near another Rio residence later in day.
``I think what's happening is that there's a lack of food in the forest which is forcing the snakes to descend to the urban areas where some residents keep chickens and ducks,'' he said.
Rio de Janeiro is home to world's largest urban rainforest with lush green jungle covering many of the city's hills.
Monkeys, tree sloths and anteaters are all common in the area.
Firefighters planned to release the snake back into the forest but would not say when or where because boas are valued here for their meat and leathery green and yellow skin.
