Matamata

About the matamata

The matamata (Chelus fimbriatus) is a South American freshwater turtle of the Amazon basin and the river system of the eastern Guianas. For years, biologists believed the species also ranged through the Orinoco basin, the western Guianas, and the upper Rio Negro–Branco system, but a 2020 genetic study found a deep split between those populations and the Amazon population. The Orinoco animals were reassigned to a new species, Chelus orinocensis, leaving the Amazon mata mata as Chelus fimbriatus — one of only two living species in the genus Chelus.

Some authorities have since updated the common name of Chelus fimbriatus to "Amazon mata mata" to reflect this narrower range.

The turtle's scientific description has a tangled history. French naturalist Pierre Barrère first described it in 1741 as a "large land turtle with spiky and ridged scales." Spanish zoologist Fermín Zanón Cervera named it Testudo terrestris in 1765, a name that clashed with one later given to the Greek tortoise, and German naturalist Johann Gottlob Schneider redescribed it as Testudo fimbriata in 1783. It was moved into its own genus, Chelys fimbriata, in 1805. Altogether, 15 different scientific names were used for the species between the mid-1700s and the late 1800s before the International Commission on Zoological Nomenclature settled the naming dispute in 1963.

Physically, the matamata is a large, sedentary turtle built for ambush. Its head is triangular and flattened, covered in tubercles and flaps of skin, with a tubular snout tipped by a small "spike." Three barbels sit on the chin, with four more filamentous barbels along the upper jaw, which is neither hooked nor notched. The oblong carapace is brown or black and can measure up to 45 cm (18 in), with adults reaching a full weight of 17.2 kg (38 lb). The plastron — the underside of the shell — is reduced, narrow, hingeless, shortened toward the front, and deeply notched at the rear. Combined with the shell's rough, ridged texture, the effect is a body that looks like a piece of bark rather than an animal. The neck, longer than the vertebrae beneath the carapace, is fringed with small skin flaps on both sides, and each forefoot carries five webbed claws. Males can be told apart from females by their concave plastrons and longer, thicker tails.

Behavior and diet

The matamata's camouflage is not just visual. As it holds still in the water, the skin flaps along its head and neck let it blend into surrounding vegetation until a fish swims within range. It then thrusts its head forward and opens its mouth as wide as possible, creating a low-pressure vacuum that pulls the prey straight in — a technique called suction feeding. The mouth snaps shut, water is expelled slowly, and the fish is swallowed whole, since the turtle's mouth is not built for chewing. When hunting in shallow water, matamatas will maneuver prey into position, surround it, and wave their front legs to block an escape route before triggering the suction strike.

This turtle is almost entirely carnivorous, feeding on aquatic invertebrates such as worms, mussels, crustaceans, and insects, along with fish; on rare occasions it will take small birds, amphibians, or small mammals that have entered the water. When researchers examined the stomach contents of 20 wild matamatas, they found nothing but small fish. Feeding happens mostly at night in muddy, low-visibility water, conditions the matamata is well equipped for: its eyes reflect light like those of other nocturnal reptiles, and the skin flaps on its neck are extremely sensitive to nearby movement.

Reproduction begins with a display: males extend their limbs, lunge their heads toward females with mouths open, and move the lateral flaps on their heads. Nesting takes place from October through December in the upper Amazon, with clutches of 12 to 28 brittle, spherical eggs about 35 mm in diameter.

Range and habitat

The matamata lives in slow-moving streams, stagnant pools, marshes, and swamps across northern Bolivia, eastern Peru, eastern Ecuador, southeastern Colombia, the eastern Guianas, and northern and central Brazil. It is a strictly aquatic species, but it favors shallow water where its long snout can reach the surface to breathe without the rest of its body being exposed.

The 2020 taxonomic split narrowed the accepted range of Chelus fimbriatus specifically to the Amazon basin and the eastern Guianas. The northernmost part of the Amazon basin, the upper Rio Negro–Branco system, is now understood to be occupied instead by the separate Orinoco mata mata, Chelus orinocensis — a reminder that this animal's range on paper has shifted even though the turtles themselves have not moved.

Conservation status

No IUCN Red List assessment is cited for the matamata. The 2021 world turtle checklist compiled by the Turtle Taxonomy Working Group for the IUCN's Tortoise and Freshwater Turtle Specialist Group treats it as Least Concern.

It does appear regularly in the exotic pet trade, where its odd appearance commands high prices. In captivity, keepers maintain warm, acidic water with a high tannin content and moderate to heavy filtration, since water quality is one of the main challenges of keeping the species. Because matamatas are not active hunters, they need less space than a similar-sized but more mobile turtle such as the alligator snapping turtle. Author David Fogel, who has kept the species, described his matamatas as quite intelligent: one learned to sit near the aquarium's spray bar at feeding time, where floating food was pushed underwater within easy reach.