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Sexual dimorphism in the species Pelusios castaneus

With Pelusios castaneus sexual differences are considerable. Size can be an indicator with adult specimens, as females can reach a carapacial length of 285 mm. while males mostly will reach typical carapace lengths of 200 to 240 mm.
Aside from this, males have a long, thick tail which is quite notable. The cloacal vent is at the tip of the tail, far outside the posterior marginal border of the carapace. Females, on the other hand, have a short blunt tail with the cloacal opening at the base of the tail. These differences might be notable with quite small specimens of 100-120 mm. carapacial length.
The anal notch is deep and V-formed in males while the anal notch is less deep and U-formed in females.

The posterior lobe and abdominal scutes are shorter and smaller in males, causing the anal scutes to barely reach the posterior marginal scutes. With females the anal scutes reach to the posterior marginal border of the carapace, the abdominal scutes are longer and the posterior lobe is broader.

From left to right: male, female, female. 

Like most turtle species, the male Pelusios castaneus has a clearly visible concave plastron, in contrary to the female, which has a flat plastron.
Overall, males of Pelusios castaneus are less broad and less domed than females are.

Breeding Pelusios castaneus 

Male and female Pelusios castaneus can be kept together without problems of aggression. Though the male will court the female frequently, the male doesn't do that in such a way that the female will be severely molested.
However, to give the female some rest, it is better to keep 1 male with 2 females.
In their natural habitat, many populations of Pelusios castaneus pass through a period with less water available to them, many habitats even drying up. When this happens, they will estivate in the dried up mud. Thus passing through a time of rest, awakening when the waters return, the turtles have their biological clocks synchronized again. Though it is proven that replicating this situation, and its subsequent behavior in the turtles, is not necessary to have Pelusios castaneus breeding effectively.
Nevertheless, because we want to be sure that the specimens in our breeding group of Pelusios castaneus have their biological clocks synchronized; we let our Pelusios castaneus pass through an estivation period.

The estivation period in captivity is initiated by letting the water temperature rise from 24-26º C to 29-30º C (75-79º F to 84-86º F). Weekly we also take out about 5 cm of the water’s depth by draining. Apart from the rising of the water’s temperature and the lowering of the water level, we also provide less food, feeding only once a week.
Once the water level has reached the depth in which the turtles can no longer get fully submerged, it is time to put them into their dry enclosure.
The dry enclosure is a tank with about half its height filled with a 50/50 mixture of gross sand and peat. The mixture can be covered with some dried leaves, but this is not necessary. The mixture itself is a little moist to start with. The dry enclosure must be kept warm, with an air temperature of around 25º C (77º F). The dry enclosure itself is best left at a tranquil place.
Before the turtles are placed in the dry enclosure, the enclosure must already have reached the needed temperature.
When Pelusios castaneus are placed into the dry enclosure, they will typically start digging themselves in within an hour. By checking on the turtles an hour later, one will only see the tips of the snouts pointing out of the substrate or not even that at all.
To prevent colder air from entering the dry enclosure, the enclosure is best covered by a sheet of plywood with some small holes in it so that oxygen can still enter the dry enclosure.
Once the turtles are estivating, once or twice per week we check them carefully and if their faces look very dried, we sometimes spray a small amount of water on their eyes to prevent dehydration (in the wild, many Pelusios turtles may die during the estivation period because of dehydration).
The dry period in the wild may take as long as six months, or in freak years maybe even much longer (with many dead turtles and other animals as a result). However, we choose not to let our turtles pass such a long period estivating. A period of 4 to 8 weeks is sufficient.

Pelusios castaneus during the estivation period. Sometimes they keep their heads above the ground, sometimes they are completely dug in. 

After 4 to 8 weeks the turtles are awakened. We do this by spraying water in the enclosure, simulating rainfall. However, it is not the intention that the enclosure turns into a mud pool either. Do remember that the temperature is allowed to drop a few degrees (like during real rain showers), but not too much.
Once we have moistened up the dry enclosure, usually within a few hours the turtles will start wandering about. Let them just be for a day. The next day the turtles are returned to their normal, wet enclosure with the water level only 20 cm high. Remember that the turtles are weakened and therefore care must be taken that they can easily reach the water's surface to breathe. The temperature of the water must be around 24-26º C (75-79º F) and the air temperature is best around 30º C (86º F). As the turtles have lost a lot of moisture from their bodies during estivation, they will drink a lot when they are placed back into their watery enclosure. For this reason, during the estivation period, the wet enclosure is cleaned thoroughly and filled with fresh, clean water.
The first days in the wet enclosure the turtles are not fed. We start feeding them on the third day, and only a little bit. The turtle's intestinal system must restart too, so filling them directly with food will cause a lot of stress on the stomach. After the fifth day we start feeding them in the same manner we fed the turtles before we started the estivation period.

Now, with the estivation period over, and their bellies full with food, the males of Pelusios castaneus will make their presence known to the females by showing off their mating ritual.
The ritual itself consists of the male swimming from behind and over the female, grabbing hold on her by clamping himself with his claws to the carapacial rim of the female and smashing his snout into the top of the head of the female. Sometimes this ritual is replaced by another form of the ritual in which the male surpasses the female from behind and below and once she sits still, the male will rub his snout against the snout of the female. If the female is receptive, the male will mount her to start the actual mating.
The actual mating may take about 5 minutes. Afterwards the male will disconnect from the female and both go their own way.

The mating ritual and actual mating.

Once the female is gravid, she will notably bask more often, spending most of the day warming up. Her food intake will also increase and the ever present cuttlebone will soon show clear bite marks.
The time that will take between actual fertilization of the eggs inside the female, and the depositing of the eggs will take about two months. Though in the wild females can lay eggs at least twice per season, in captivity a female  will typically nest only once per year.

With the moment of depositing the eggs nearing, the female will start to dig holes in the substrate where she is supposed to lay eggs. These first holes are just for trying out the substrate. Once the female has actually laid her eggs, she will not be spending so much time basking as seen before the actual egg depositing.

A female Pelusios castaneus digging a nest.

A good manner to find out if the female has actually laid eggs is weighing her. During the ultimate weeks of being gravid, an increase in weight is quite notable. Once the female has laid, a decrease in weight will easily tell you she has laid.
Female Pelusios castaneus don’t cover up the nest hole very neat. It is easily located. Once we are convinced the eggs are laid, we start digging for the eggs to place them in the incubator. The eggs are encountered quite deep: the first eggs are found at a depth of around 15-20 cm with the last eggs found about 10 cm deeper. The eggs are laid with their tips pointing up, standing vertically in the substrate.

Female Pelusios castaneus bury their eggs quite deep. 

The result of digging for eggs: 20 eggs were dug up. The eggs were immediately placed in an incubator.

Typical Pelusios castaneus eggs measure 20-22 x 40-45 mm. The eggs are first a little bit smooth and slippery, but within a day they will develop a white powder on the outside and they will feel a little bit rough. This indicates that the egg is “chalking up”.

At one location, a female of 26 cm carapace length deposited 20 eggs in the nest; other females with carapace lengths of 16-20 cm have laid clutches of 7 to 14 eggs. The eggs are then placed in an incubator of the “au-bain Marie” type. This means the eggs are placed over water, which is warmed to the desired temperature. The incubator is a closed system so the humidity in the incubator remains a constant 80-90%, the desired humidity. Pelusios castaneus eggs seem to need such a high humidity, lower air humidity values seem to result in lesser hatching results. Temperature is a constant 29- 29,5º C. If vermiculite is chosen as the breeding substrate, than gross vermiculite will be the best choice because it allows a better oxygen exchange than fine vermiculite. Some breeders have reported lesser breeding results when using fine vermiculite, the fine vermiculite causing hatchlings to die of oxygen shortage. Fine vermiculite seems to block a good gas exchange.

Like most present day’s turtles, Pelomedusidae are turtles that have a Temperature Sex Determination (TSD). This means that the sex of the hatchling is determined during its development in the egg during the first stage of incubation. With a constant temperature of 29-29.5º C, hatching of the turtles commences after 55-60 days. Most hatchlings of Pelusios castaneus in captivity hatch with some small remains of the yolk sac. This is caused by the fact that hatchlings in captivity don’t have to dig their way up to the surface, like in the wild. In the wild hatchlings will absorb the yolk sac remains during their digging towards the surface.
In captivity it is better to leave the hatchlings for a few days in the incubator, until the yolk sac is fully absorbed.

After 55-60 days, the eggs will show the first cracks, indicating the hatchlings are about to hatch. 

Most hatchlings have a small part of their yolk sac still visible. 

When hatchlings have just hatched, they are very dark, nearly black colored. 

Note the egg tooth on this hatchling.

Once the hatchlings have fully absorbed their yolk sac, they can be placed in a plastic box or small aquarium with about 10 cm of water depth and sufficient rocks or bricks to crawl on to come out of the water to bask.

Even between hatchlings from one clutch there is quite some variability in belly coloration.

After the first couple of weeks the hatchlings will become overall more light colored.

Note the differences in coloration in the same clutch. 

The same hatchling, right after hatching and 3 weeks later. Clearly visible is the change in coloration and contrast.

It appears that P. castaneus eggs have an upper and lower limit for successful incubation. P. castaneus eggs incubated at 26ºC failed to develop beyond the initial stages and it is recommended that 27ºC be established as the lower limit. Additionally, two clutches experiencing a temperature spike of 30-32ºC for three days resulted in loosing all twenty-five eggs within a week of hatching (all embryos were fully developed). Pelusios castaneus eggs are not as resilient as Pelomedusa s. subrufa eggs incubated in the same containers (in 1/3 sand to 2/3 peat mixture) experiencing the temperatures described above, though 26ºC yields poor hatching results with Pelomedusa.

The egg on the left was opened after 50 days, the one on the right was opened after 97 days. Both were opened manually after it was clear they had gone bad.

Hatchlings of Pelusios castaneus are best kept in a plastic tub for the first weeks of their lives. This way they are easy maintainable and observable. They like to hide under aquatic plants.