Pelodiscus sinensis / Chinese softshellturtle - Care

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Specification Description
Class: Reptilia
Order: Testudines
Suborder: Cryptodira
Family: Trionychidae
Scientific name: Pelodiscus sinensis
Dutch name: Chinese weekschildpad
English name: Chinese softshell turtle
Dieet: Carnivorous
Average age: 30+ years
Distribution: Asia
Lifestyle: Aquatic
Reproduction: oviparous / egglaying
Status: Vulnerable
Cites: non

Pelodiscus sinensis, (Wiegmann, 1835)

This is the third article in our #terrariumlibrary about a softshell turtle, of which these and possibly the Apalone spinifera ssp (males) are 'most' suitable for captive husbandy. The Pelodiscus sinensis is the most common of these species. Not because it is very common in the wild, but because it is bred in large numbers (read, millions) in 'Farms' in Asia, mainly China and Taiwan. There are more than 1400 of these farms to meet the demand for turtle meat and parts for mainly the Chinese and Vietnamese markets.

None of the turtles are a wise choice if you start with keeping turtles. This mainly has to do with their character, size and the shell. Nevertheless, this species seems to be the best option for someone who wants to take the step to his first softshelled turtle. In this article you will find some points that you want to pay attention to.

 

Description:  Pelodiscus are remarkably good and active swimmers. The most remarkable external characteristic is the shell. In contrast to the known terrapins and tortoises, soft shell turtles do not have a hardened bone shell but a rather flexible 'leathery' one. This shell is connected to a bony plate under the shell. But these hard parts are missing in the rest of the carapax. Also in the plastron, the bone plates are very reduced and not connected. The plastron is moderately reduced but this turtle can retract its head, front legs and partly the rear legs inside their shell. This flexible and flattened shell ensures that these turtles can easily swim quickly or hide in the silt on the bottom of the waters where they live.

The neck is long and can be quickly stretched to catch a prey. The head is very pointed with a clearly elongated nose. In this way, the turtles can easily breathe in the air without being seen on the surface. The lips have a fleshy edge but behind them is a very sharp, powerful beak. The powerful bite allows turtles to easily rip fish into pieces or crush shellfish. They are powerful swimmers with long legs and clear webs between their toes. The nails are hardly visible, except for the front toes on the front legs (especially in men).

The tail of both the male and the female is relatively short, although the one of the male is a bit longer. The male however has the cloaca is placed entirely at the end of the tail where the females cloaca is positioned closer to the plastron. The males plastron is not concave like seen with many terrapins and tortoises. Adult males are on average smaller (20 / 26cm shell) as the females (30 / 33cm shell) but the difference is not as clear as with some other species such as the Apalone spinifera.

The shell and body has an unremarkable light brown / beige colouring and the plastron is almost white. On the plastron, an unclear pattern of small dots can sometimes be seen in young animals. An irregular pattern of light spots can be seen around the face and mouth. The eyes have a clear yellow coloration.

The Vietnamese form has a clearer pattern of enlarged round spots on the carapace. These round dark spots can also be seen on the plastron. Because large numbers of this species are cultivated, different variants or morphs are regularly found. The albino is therefore quite 'common' and very popular in captivity. In addition, melanistic (black), 'Piebald', Paradox and Leucistic animals have also been found.

 

Natural distribution and habitat:  This turtle has a very wide range and adapts easily. As a result, they are unfortunately also invasive in other areas where they compete with the native species of turtles. Despite their large range and the large numbers that are bred in farms, the natural population seems to be greatly reduced by pollution, the loss of natural habitat and the poaching of the populations for the food market.

Their habitat naturally consists of large open waters, rivers, lakes and marshes. In areas where they are invasive, they can also be found in drainage systems, slow-flowing pools, ponds and streams. They can be found in both fresh and brackish water. To survive in this brackish water, the turtles 'urinate' through their mouths. In their mouth they have a number of glands that excrete waste and urate. By opening their jaws, they rinse the waste out without ingesting brackish or salt water. Around their cloaca, the animals also have glands that can absorb oxygen from water, allowing them to stay under water longer.

This turtle naturally occurs in South, Eastern and central China and on Taiwan. According to a recently released article, the populations in Northeast China, (Southeast) Russia and the Korea's are now Pelodiscus Maakii. Populations from Northern Vietnam are now named as Pelodiscus parviformis and the Pelodiscus axenaria in Hunan (China). Populations in almost all of Japan, Malaysia, Sumatra, Kalimantan and Borneo, the Timors and Iran historically originate from deliberate releases and escaped animals from food markets. Outside Asia they now also occur in Hawaii, in Spain, Guam and Florida in the USA where they compete with the indigenous species. These populations originate from escaped or intentionally released Pelodiscus.

 

Behaviour:  Pelodiscus sinensis is a very active and good swimmer that can maintain itself both in deep waters and shallow ponds. They seem to prefer some slightly turbid water which helps in stalking their prey. They are active hunters but can also behave like assassin. By hiding in the sludge layer at the bottom of the waters where they occur they are almost invisible thanks to their shield and color. Here the animals can quietly wait with only their eyes that are placed on top of their head visible. As soon as a fish swims over, they stretch their necks at great speed. Because of their long stretching neck and open mouth, a vacuum is created that, as it were, sucks in their prey. A very effective way of hunting that one will see relatively little in captivity due to our way of keeping and feeding.

This species is very bound to the water but can move on the land rather quickly. In the night, after rain, they are sometimes found in wet fields looking for new habitat. Besides that, it is a mainly day and dusk-active hunters who hide in the night on the bottom under trunks or buried in the silt.

The assumption is often made that these and other species of softshell turtle do not sunbathe and there are species that are almost never found sunbathing. The Pelodiscus sinensis seems to do this even though it is less like the famous terrapins. Mainly on sandbanks near the water so they can quickly dive into the water in case of disturbance. In places where they cannot easily get a sunbed they will look for shallow waters. Here they hang on the surface to sunbathe and thermoregulate as shallow waters heat up faster. Males are found considerably less on dry land than their female counterparts. Partly because the females have to warm up more for the development of their eggs and of course for the egg-laying itself.

One of the possible reasons why people see this species less frequently sunbathing comes from their shell. This adaptation makes it a very fast swimmers but offers considerably less protection than the hard shields of other turtles and is therefore, especially as a young, more vulnerable and easier prey. It also seems easier to let UVB 'through' so that less long and intensive sunbathing needs to be done in order to start the same Photo-biosynthesis process to make pre-vitamin D3. As a result, sunbathing on the water surface can already be sufficient and they do not have to leave the safety of the water for this.

In the natural habitat they share their habitats with many other species of turtles. However, these are very territorial species, mainly against other softshell turtles but also towards other turtles. They are also very boisterous and powerful swimmers. Combining this turtle is therefore, unless you have a very large turbid pond, absolutely not recommended. If groups of Pelodiscus or other soft turtles are offered at an expo or in the pet store, you will often find specimens with bites and wounds at the edges of the shell, especially along the back sides. These are inflicted by other Pelodiscus in combat or during food competition.

Pelodiscus sinensis is very active in captivity and is full of character. Young animals can be shy but they quickly recognize their caretaker as a source of food. No distinction is made between actual food items or a finger. A bite can be very powerful. Outside the water, they feel very uncomfortable and will defend themselves as soon as they are lifted out of the water. In addition, their soft, wet shell does not help with easy handling. The long neck allows them to easily bite their 'attacker'. Therefore, do not hold the animals any longer as needed and place them directly in a container if you have to move them. It is best to grasp this turtle firmly at the back with one hand and then support it with the other.

 

Housing:  There are a number of points that you want to consider if you want to take care of Pelodiscus or other softshell turtles in good health. The most important are water quality, light and space. Pelodiscus sinensis is an active swimmer and mature females become quite large. This means that you need a lot of space to house these turtles. We recommend at least 150 liters of water per 10cm shell length. That is at least 450 liters of water (150*60*50cm) for a single adult female and preferably larger. Young Pelodiscus can be raised in an aquarium of 100 cm long x 40 cm wide and a water depth of 30 cm or higher. This brings us to an 'advantage' of these turtles above some others. Youngsters are immediately very powerful swimmers and thus easily swim to the surface. That is why the water part does not have to be shallow and so you can immediately offer a lot of swimming and living space. Offer objects on the surface where the turtles can rest such as floating plateaus, vegetation and (tropical)wood. Offer a place where the animals can dry up and sunbathe at all times. For young and adult males this can be a simple plateau. Egg-laying females should also have access to an laying area with a sand/soil layer of 20cm or deeper and an square area of ​​60x40 or larger. Female specimens that are always kept separate can also develop eggs. These are then unfertile and are usually deposited in the water. But some females do not do this and then need a spot on the land to lay their eggs. If this possibility is not present, there may get egg-bound which can become fatal.

A heat lamp should be placed above the basking dock where the turtles can warm up and dry underneath. The hot zone must reach a temperature of 32C. UVB is definitely important for these turtles, but it must be well distributed and not too concentrated on a single site of the shell to prevent burns. For this reason one can use a high quality UVB T5 fluorescent tubes above both the basking location and the water. Place a reflector behind this fluorescent tube to spread the UVB rays over the living area. If the distance is too great for the use of T5 lighting, then HQL or HID lamps with a wider radius than the average spotlight are a good option. UVB is very important for the health of the shield and the turtle itself. The air temperature should be 25C on average and the water 25/26C. Due to the great adaptability of this turtle, it can withstand night-time cooling’s and generally cooler periods. As a result, they can also be kept outside in a large pond for a part of the year (avoid escape). This means that additional heating at night is often unnecessary. If you use a thermostat heater then it should be well protected to prevent damage to the heater or turtle.

Pelodiscus sinensis seems to be less sensitive than some other softshell turtles and is therefore also a better choice for someone who starts with the housing of these type of turtles. The shell, however, is more easily damaged than those of tortoises with a horned shield. If there are a lot of bacteria and dirt in the water, these damage can not heal properly and infect or fungus spots occur due to poor water quality. A good filtration is therefore of great importance. Provide a lot of commotion and movement in the water by using air stones and a powerful filter outflow. The best thing to do is to choose external filtration in which both biological and mechanical filtration takes place. Use a pre-filter to keep the external filter clean longer so that biological filtration can do better and longer work. Change a part of the water and clean the prefilter weekly. The aquarium or pond can best be set up simple in order to provide as much swimming space as possible. However, some decoration does provide enrichment and offers visual barriers. Placing some pieces of wood that also reach the surface and large half terracotta pots as a hide is therefore an option. A layer of river sand on the bottom is advisable and offers a big natural shelter for these turtles. It is best not to place heavy stones or boulders in the aquarium as they are easily moved by the powerful turtle. Plants also do not live long because they will be continuously turned over. Therefore it is best to place various floating plants in the water. Once again they provide a natural shelter, give a natural look and the roots of these plants extract waste such as nitrates from the water and thus serve as an extra filter.

 

Combining with other turtles:  Young animals could be kept in small groups provided there is sufficient space and shelters for this. But it is best to keep this species absolutely separate from other turtles. They are very territorial and can constantly bite and chase other residents. Partly because, however regrettable, there is often simply too little space for the turtles to avoid each other. Many considerably smaller turtles are sometimes left alone but will get stressed by the active and turbulent behaviour of the turtle or seen as prey. If you combine, which we do not recommend, do this with the same size or larger, very active species of terrapins that occur in the same area. And only in a very spacious enclosure which often means an outdoor pond. The advantage of a pond is, besides the larger living space, the fact that there are many more visual barriers here. This can be due to obstacles, vegetation and turbid water.

 

Combining softshell turtles with fish:   The average turtle lover also has affinity with other animals, including fish. In addition, we more and more see that softshell turtles are purchased as 'cool' addition to an aquarium with so-called 'Monsterfish' (large predator fish). After reading this article we hope that this choice is re-considered. The turtle will get many years older than the fish and although this species is very aquatic, there should be opportunities to get on land and dry in combination with UVB.

However, this species seems more suitable as some other turtles to combine with larger active predatory fish. Partly because it is also an active swimmer and can also maintain itself well in deeper waters. In addition, they can live within a range of different temperatures, provided that the important basking site is available. If you want to combine this turtle with predatory fish. Then make sure there is space for the turtle to dry and sunbathe and place that important UVB lighting. Filtration will have to be in order in connection with the polluting predator fish. The best thing is to set up the aquarium to the requirements of the turtle and to find out suitable fish to combine. Keep in mind that these turtles are very good predators and will also try to overpower prey that are too big for their mouth. The damage a turtle can cause is great and often fatal for a fish. Also keep in mind that some catfish can carry strong spines for protection. These can actually damage the Pelodiscus if it bites into it. 'Monsterfish' are not called monsters without a reason, they grow big and have a monstrous appetite and are very boisterous, too boisterous fish during feeding means possible stress for the turtle. Therefore combine Pelodiscus only with fish that are not obviously bigger and/or more active and only if the Pelodiscus is a few years old.

Although there is a risk, these turtles can possibly be combined with (Asian) predatory fish such as: (Snakeheads) Channa argus, Channa marulioides and other bigger species, Hemibagrus sp.  Asian Silurus and other Asian catfish. Pangasius sp, Chitala sp (Clown knifefish), Datnoides (Siamese Tiger Perch), Scleropages formosus (Asian arowana), Oxyeleotris marmorata (Marble goby), Big Zilvershark barbs (Balantiocheilus melanopterus), although these will probably be food to an large Pelodiscus sinensis or some calmer carp species. You can also look at similar species from other regions but if we are combining we might as well try to recreate some sort of an biotope. Another option could be very small fish such as Danio’s. Or just no fish at all ?. Some fish may feed on the leftover food of the turtle but will also create a heavier bio-load on the water. Therefor more filtration and work to keep the water clean is needed.

 

Diet:  The Chinese softshell turtle is almost completely carnivore. As they grow older, they can seasonally also eat some water plants and/or fruits, but they are absolute hunters and need a diet with lots of proteins and fats. Young turtles in particular do not immediately accept pellet food, although they seem to be fed with it in the farms where they come from. Feed as varied as possible, preferably with whole prey. You can feed young animals every other day and adult animals 2 to 3 times a week. Feed with bloodworms, tubifex, earthworm, mussel, shrimp, smelt, roach, grasshoppers, meal and super worms, crickets, Dubias and other larger insects. As soon as the animals accept pellet food, you can offer this as a staple diet and vary with the aforementioned items.

 

Reproduction:  Despite the large numbers that are produced in farms, they do not seem to be bred in high numbers by hobbyist or Zoo’s. Especially in Europe where the species is imported in large numbers from these farms. Since no animals are imported under 4 inch (10 cm) or can be transported over State lines in the USA, the number of Pelodiscus found here is considerably lower and the prices are also higher. Here in higher, but still not great numbers, degree they do get bred (mostly in outside ponds). One can possibly deduce here that in Europe simply the 'effort' is not taken to bring this species to reproduce. The species is relatively inexpensive and given the large space and costs that a couple needs outside of the mating season to house them, this does not seem to be worthwhile. In addition, pairings are very rough and a female can be seriously injured. Especially if it is not ready to mate. The introduction must therefore be well timed. In farms the turtles are kept in such large numbers on such a small area that territorial behavior is reduced. Possible losses due to fighting are hereby accepted and calculated in. The factor of 'timing' is therefore less relevant here.

Images of mating (attempts) show that there is no form of courtship behaviour. As soon as a male sees a female, he goes after it, bites her firmly in the neck, a front leg or other part on the shell, holds her tightly with his powerful legs and pushes his cloaca against hers. The females seem to be very aggressive, depending on her mood. As soon as the actual copulation takes place, the female calms down somewhat. The duration of the mating is very short and as soon as it is over the male swims away, often while the female chases him. It is therefore important to separate the couple immediately after mating to prevent fights and injuries. Females sometimes lay a number of 8 to 15 eggs a couple of times a year. These eggs can be hatched at temperatures of 26C to 32C. The average incubation period is 65 days at a temperature of 31C. Young are 25mm long and immediately very good swimmers although they will stay in shallower parts of their waters in the initial phase of their lives. Partly because they heat up faster and here small prey live whilst they are safer for natural predators such as birds, other turtles, big fish, Varanus sp or other reptiles. Adult animals are mainly eaten by crocodiles, felines and humans.

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