Natural History
Chelus fimbriatus, or matamata, is perhaps one of the strangest looking animals in the world. A large aquatic turtle native to South America, it is the only member of the Chelus genus in the sub-order Pleurodia. The turtle lives in slow-moving rivers and oxbow lakes and primarily eats fish. This turtle is one of the most unique predators in the world and has some specific husbandry requirements.
Matamatas have a very long carapace, sometimes up to 18 inches (45 cm), with three knobby keels running down the carapace. The anterior and posterior ends of the carapace are serrated, more so in the posterior. Generally, both the shell and skin are reddish-brown in color, but geographic variations can occur as discussed below. The most distinctive feature of the matamata is its neck and head. The neck is usually longer than the turtle shell with many fleshy lobes on the sides. The head is flat with an arrow-shaped appearance, and large tympana are on either side under a triangular shaped fleshy lobe with a long (about 1.5 – 2 cm in adults) snout. The legs have rough scales and webbed feet with five claws on the front feet and four on the back. Like most turtles, male matamatas will have a concave plastron and a longer tail.
The matamata is in the class Reptilia, the order Testudines, which are all extant species of turtles. It is in the sub-order of Pleurodia, or the side-neck turtles. The matamata falls into the family Chelidae, and it is the only species in the genus Chelus.
The scientific name Chelus fimbriatus translates from Latin to “fringed turtle.” Matamata is a widely used and accepted common name which translates to “It kills, it kills” in Spanish. However, the name is of Brazilian origin and is actually based on an Indian word for “skin” and doubled for emphasis (Pritchard, P. C. H. and Trebbau, P. 1984). Pritchard (1984) states that the vernacular names “caripatua” and “jicotea” are commonly used to refer to this turtle. Another common name in Venezuela for the matamata is “la fea” which means “the ugly one”. Other Indian tribes throughout the turtles range also have various names for it.
The turtle is quite common in the Amazon and Orinoco river basins. On the map below, the Amazon is in brown and the Orinoco is in red. The matamata is generally found in northern Brazil and Bolivia, Eastern Peru and Colombia, the majority of Venezuela, and some areas in Guyana. A population of matamatas also exist on the island of Trinidad (Murphy, J. 1997).
There has been some noted difference in color based on the locale of the turtle. Some of the turtles have different neck markings or color. The turtles that live in the Amazon river basins have a different carapace shape than the turtles that live in the Orinoco river basin. The turtles from the Amazon river basin have parallel sided or constricted shells. The Orinoco matamatas have a have convex sides, in some cases, an oval appearance (Pritchard, P. C. H. and Trebbau, P. 1984).
That matamata is strictly an aquatic turtle. It lives in slow-moving rivers, oxbow lakes, shallow, muddy lakes, swamps, marshes and even stagnant pools of water (Ernst, C. H., Barbour, R. W. 1989). The water this turtle inhabits is generally very dark or murky. Although some of the turtles in Trinidad had barnacles on their shells that indicate prolonged exposure to salt or brackish water (Murphy, J. 1997). The matamata rarely ventures into deep water. Even though the matamata is completely aquatic, it is not a very good swimmer and prefers to walk along the bottom. It prefers a habitat where it can rest on the bottom and extend its snorkel-like proboscis to the surface. Observations of one matamata in captivity have shown that the turtle will rarely extend more than the tip of the snorkel out of the water. Turtles found in the same habitat include Podocnemis vogli (Savannah Side-neck) and P. unifilis (Yellow-spotted Amazon River Turtle). Other animals that are known to reside in the habitat are the piranha and Caimen crocodilius or the Spectacled caiman (Pritchard, P. C. H. and Trebbau, P. 1984).
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Matamatas are notoriously immobile. They can hold their breath underwater for long periods of time and rarely move. This lack of movement results in the growing of a dense coat of algae on their shell, which aids in camouflage. This turtle only ventures out of the water to lay her eggs. Matamatas will never bask and are rarely, if ever, seen floating on top of the water.
The eating behavior and mechanics of the matamata are probably one of the most studied aspects of this turtle. When a fish approaches a matamata, the turtle will quickly open its mouth and expand its neck. This motion creates a large suction that draws fish and water into the turtle’s mouth. The water is expelled and the fish is swallowed. Even though the turtle’s head darts forward, tests have demonstrated that the prey is, in fact, captured through suction (Lemell, P. et al. 2002). There is some debate on whether the turtle actively hunts prey or is completely an ambush hunter. Holmstrom (1978, 1991) noted, on two occasions, that 2 different matamatas in captivity in different locations demonstrated different methods of prey herding. The first one occurred at the New York Zoological Park. The turtles would wave their arms and herd the fish into a shallow part of the pool and then consume the fish (Holmstrom, W. F. 1978). The second event was at the Beardsley Zoological Gardens. The turtles here would herd the fish into a corner of their aquarium and raise the posterior end of their bodies, which seemed to block the fish in the corner where they could be easily consumed. The turtles have demonstrated the ability to learn the best ways to obtain prey based on their environment (Holmstrom, W. F. 1991). Other researchers note that there are 3 main predatory behaviors: actively searching, ambush, and density dependant that is a combination of the other two. The matamata is a well-known ambush hunter but has been noted to actively search out prey when there is a high density of prey available. If the prey amount is limited, the matamatas will hunt in an ambush mode (Formanovic, J.D.R., et al, 1989).
The adaptations of this turtle make it one of the most unique animals in the world. The shell and legs look very similar to most aquatic turtles. In fact, the shell and legs closely resemble another sedentary ambush hunter, Macroclemys temminckii, or the Alligator Snapping Turtle of North America. When looking at the neck and head, one would see something that should be in Star Wars, not the Amazon rain forest! Here the matamata is the definition of form equals function. The neck and head, while looking quite bizarre, are extremely important adaptations the turtle has to allow it to catch prey. The neck is outlined in many irregular shaped fleshy lobes. Much discussion has been done on the purpose of those odd fleshy lobes. The three main theories for the purpose of the lobes are camouflage, prey detection and prey luring. A test was performed to attempt to find out what they really did. Hartline (1967) noted the results of this testing. In one test the eyes of the turtle were covered and the turtle was still able to capture prey within one hour. In other tests, a turtle had the fringes excised and it was unable to capture prey. Other tests show the highly enervated fringes would respond to a displacement of .1mm! In fact, the turtle has different nerves to determine the difference between movement and touch. The test’s final conclusion was that the lobes are used in prey detection, but also mentioned that they could wiggle slightly and that might help capture prey. The irregular pattern does break up the “turtle” pattern that would make it not look like a predator. It is also believed that the large tympana on both sides of the head are able to detect vibrations and aid in the location and triangulation of prey (Alderton, D. 1998).
