Variations: Howler monkey snake
Guariba-boia, the “howler monkey snake”, can be found in a wide stretch of the Amazon river, from Fonte Boa in the west to Urucurituba in the east, and in the lakes of the Rio Negro. It excavates tunnels in murky river bottoms, and hides in mud or thickets of water-plants. Usually its voice is the only sign of its existence.
As the name implies, a guariba-boia typically has the head of a howler monkey (guariba) on the body of a snake (boia). Sometimes it has the body of a howler monkey and the paws of an otter, and rarely it has the head of a sloth (although such a feature would seem hardly intimidating). Guariba-boias grow to about six meters long.
Guariba-boias announce their presence with loud, resonant howls that sound like an entire troop of howler monkeys. They roar from below water, and their calls are particularly loud on rainy nights.
While not as big as boiunas, guariba-boias are armed with needle-sharp fangs and lethal venom. Death by guariba-boia bite is swift and painful, after which the creature swallows its victim whole. A guariba-boia does not regularly seek out human prey, but will overturn canoes and kill the occupants if hungry enough.
Smith, N. J. H. (1996) The Enchanted Amazon Rain Forest. University Press of Florida, Gainesville.