Dyson’s Domain.
Mata mata Turtles (Chelus fimbriatus) in captivity.
By Paul H Eversfield April 09.

Biology:
A monotypic species of the Chelidae family, the Mata mata (Chelus fimbriatus) is one of the most enigmatic of the side neck Turtle species. Its crepuscular leaf like appearance which disguises a powerful vacuum like jaw, makes it a consummate stealth hunter, of its favored diet live Fish.
Their natural range, is a huge area of the Continent of South America, and extends too much of the lower catchments of both the Amazon and Orinoco river systems. This also includes the Caribbean island of Trinidad. Whilst, common in certain localities, their crepuscular nature means that they are seldom seen, and only a few of the South American tribes include them as part of their diet. Potentially, this species can grow very large and examples of adult Turtles of 50- 60 cm have been recorded.
Unmistakable characteristics, such as their wide flattened head, and sardonic smile like expression, make them easy to recognize, and as poor swimmers these monstrous bottom walkers are the mobile Fish traps of the Chelonian World in South America. The distinctive snorkel like nose is also a telling feature of this species, and the flattish carapace, with its deep ridges again so characteristic, especially in the young of this species. In nature, they tend to be nocturnal, hunting by stealth as unwary fish are often drawn to within strike range by the fleshy appendages around the head and neck of the animal. Algae and other plant material often grows on these appendages and almost always adorns the Carapace, which ironically is often used as a garden by small fish, and is tended and grazed as a prime piece of aquatic real estate. Whilst hunting, the Turtle will frequently herd shoals of prey fish by wafting one of its forelimbs and corralling the shoal to within a strike range. Feeding in these Turtles is by opening the mouth at lighting speed, and creating a vacuum in the throat, literally sucking the prey into its chasm like jaw.
There are at least two distinct races of this species which can be defined from their locality, one from the Amazon river drainage which has an almost rectangular Carapace, and tends to be a dull brown in colour, with dark almost black Plastron, the second race, from the Orinoco river drainage has a more oval shaped Carapace, and the colour, certainly of the underside is often a vivid pink, with dark black spots. These are particularly noticeable in the very young animals.


Life in Captivity:
I have kept this species for many years, and have reared, my female, from a very young, almost hatchling. She is the Orinoco form. Typical of all my “Bottom walking” Turtles, I recommend a depth of water no deeper than the outstretched neck of the Turtle, and in the young 10-15 cm prove ideal. Obviously, this depth increases with the growth of the Turtle, and an adult has no trouble at all in water up to 60-70cm. Water quality is important and where possible soft rain water is preferred. Water temperature of 28-30 degree Centigrade is maintained with a submersible aquarium heater, and filtration is via an external canister filter, with Zeolite, and activated carbon, as a medium inside the canister. I have found that very quiet water conditions with very little current is best and cover is provided with water plants and Bog wood. As these definitely are not a basking species, lighting, whilst provided, is dappled and not too bright. My Mata mata turtle tank has good natural light filtered through a polycarbonate Conservatory like roof, as well. This means plants grow well and are grazed by a few small guppies, (Poecilla reticulata) and a good number of Apple Snails ( Pomacea bridgesii). Whilst my large female is now fine with these, I tragically did lose a young Mata mata once to a chocking episode, with a snail. I think it dropped of the side of the tank, and triggered a feeding strike in the young turtle, which could not regurgitate this accidental prey item. Therefore care should be exercised, with such tank mates!
The young Mata mata turtles were initially fed live fish, and after a fairly short period of conditioning and acclimatization were weaned onto fresh dead fish offered on tongs. Their diet is entirely Fish so I try to give variety, with Fresh Trout, Eel, Chinese gobies, and other small bait fish commonly used by anglers. However, I do avoid giving any of the Carp family, and only very seldom would I use salt water varieties such as whitebait, Lance fish, or Mackerel. This is because of the risk of Thiaminase poisoning, which again through tragic experience I have encountered, with this species. I do also recommend using a Vit D3 supplement, either injected into the food, or in the case of nutrobal dusted over the fish prior to it being offered. As my animal has a very good feeding response and has been conditioned to associate my feeding tongs with a meal, this is not difficult to administer.
As these are quite sedentary in nature, I only feed once a week and will two or three times a year give one very large meal in a month.
For general husbandry, I also give a 30% Water change every week, and avoid handling the animal if possible at all. These are very easily stressed and require quiet, settled environment, with minimum of disturbance.
Though, I have not bred this species they are now bred by a few specialists in captivity in Europe, USA, and even a few in South America. For those interested in a highly specialized Piscovour hunter, the Mata mata makes a fascinating captive Turtle and with care will live for very many years in captivity.
For me, Dyson as she is known is an enchanting Turtle with great character and presence.

References;
Keeping and Breeding Freshwater Turtles- Russ Gurley 2003 Living Art
Experiences and Observations of Chelus fimbriatus, the maintenance in terrarium and successful reproduction- Herbert Meier & Ingo Shafer 2003 Radiata, journal of DGHT-AG
Captive breeding of the Mata mata Turtle, P Drajaske 1982, Six annual Reptile symposium on captive Propagation and Husbandry