The Mata mata is a large freshwater turtle found in South America. It has a triangular, flattened head with many tubercles and flaps of skin, and a "horn" on its long and tubular snout. The Mata mata's oblong carapace is brown or black in color. The plastron is reduced, narrowed, hingeless, shortened towards the front, and deeply notched at the rear with narrow bridges. These may be meant to allow the turtle to resemble a piece of bark, camouflaging it from possible predators. The plastron and bridges are cream to yellow or brown. The head, neck, tail, and limbs are grayish brown on adults. Hatchlings show a pink to reddish tinge in the underside edge of their carapaces and plastrons that gradually disappear as they grow. Each fore foot has five webbed claws. Males have concave plastrons and longer, thicker tails than females.
Mata matas occur in South America, primarily in the Amazon and Orinoco basins. Their range extends into northern Bolivia, eastern Peru, Ecuador, eastern Colombia, Venezuela, the Guianas, and northern and central Brazil. These turtles live in slow-moving, blackwater streams, stagnant pools, rivers, marshes, and swamps. Mata matas are strictly aquatic but they prefer standing in shallow water where their snout can reach the surface to breathe.
Mata matas are solitary creatures. They predominantly feed at night in muddy water with limited visibility. However, these turtles are well adapted to hunting in these conditions. Mata matas have very fine eyesight with eyes that reflect light, similar to other nocturnal reptiles. In addition, the skin flaps on the neck are also extremely sensitive and help them detect nearby movement. Mata mata turtles use a specific method of seizing their prey. The appearance of their shell resembles a piece of bark, and their head resembles fallen leaves. As they remain motionless in the water, their skin flaps enable them to blend into the surrounding vegetation until a fish comes close. They may also move the prey into shallower areas of water, surround the prey, and wave their front legs to prevent them from escaping. Once surrounded, these turtles will open their large mouth as wide as possible, creating a low-pressure vacuum that sucks the prey into their mouth, known as suction feeding. Turtles then snap their mouth shut, the water is slowly expelled, and the fish is swallowed whole; Mata matas cannot chew due to the way their mouth is constructed.
Mata matas are polygynous meaning that males mate with more than one female in a single breeding season. During this time males display for females by extending their limbs, lunging their heads toward the females with mouths agape, and moving the lateral flaps on their heads. Mata matas breed and nest from October through December in the Upper Amazon. Females usually lay 12 to 28 brittle, spherical, 35 mm-diameter eggs per clutch. The incubation period lasts around 200 days. Once the egg are laid females leave the nest. Hatchlings are fully developed at birth and don't require parental care.
The biggest threat to Mata matas is the collection for the exotic pet trade. Due to their unique appearance, they make interesting display animals and are especially popular in Europe and the United States. Climate change and habitat loss could be potential threats to this species in the future.
Mata matas are important predators in their ecosystem. They feed exclusively on small fish and aquatic invertebrates and this way help control their populations.