Key Techniques for Artificial Incubation of Chinese Softshell Turtle Eggs

1. Collection of Chinese Softshell Turtle Eggs

(1) Preparations before collecting Chinese softshell turtle eggs. Before the parent Chinese softshell turtles enter the egg-laying season, the egg-laying site should be repaired and tidied up in a timely manner, holes should be plugged and filled, the egg-laying site should be loosened by digging, and fine sand should be spread evenly, and the moisture of the sandy soil at the egg-laying site should be adjusted so that it forms a ball when held in the hand and crumbles when lightly shaken with the hand released. During the egg-laying season, the egg-laying site should be carefully checked every morning to see whether there are traces of female Chinese softshell turtles laying eggs. The inspection should be carried out before the sun rises and before the dew has evaporated. If new soil is found to have appeared, along with claw marks of Chinese softshell turtles and a smooth soil surface, then it is an egg-laying nest of a female Chinese softshell turtle. At this time, a small stick can be inserted beside the nest as a marker for later digging and collection.

(2) Prepare the tools for collecting Chinese softshell turtle eggs. These include a small iron shovel or bamboo stick for digging soil, as well as special wooden boxes, plastic baskets, basins, and so on for holding eggs.

(3) Collection of Chinese softshell turtle eggs. Before collection, the tools should be washed clean and disinfected for later use. After the egg collector enters the egg-laying site, they should dig and collect nest by nest in sequence according to the markers. When digging, the loose soil sealing the nest entrance should be brushed aside gently, layer by layer. When brushing aside the nest soil and enlarging the nest entrance, one must be careful not to break the eggs, and then use the thumb and index finger to pick out the eggs one by one from top to bottom, and gently place them in the egg collection box. When placing the eggs, they should be placed gently, firmly, and steadily to avoid breaking them. When collecting eggs, attention should be paid to checking the fertilization status of the eggs. High-quality eggs with clearly visible animal and vegetal poles, a round small white spot on the top of the shell, a smooth and glossy shell, a milky white or pink shell color, and a large and round shape should be gathered together. If the shell of a collected egg is not round, it is a deformed egg and should be placed in another container, not mixed in randomly. If no transparent white spots can be seen around the eggshell, then it is an unfertilized egg. If the white spot on the shell is not round but irregular in shape, and the animal and vegetal poles are unclear, then it is a weakly fertilized egg. These three kinds of eggs should be placed separately and cannot be incubated together. When collecting eggs, generally the ones marked the previous morning are collected the next morning; they cannot be collected on the same day they are found.

2. Incubation Methods for Chinese Softshell Turtle Eggs

Chinese softshell turtle eggs can be incubated either in indoor incubation boxes or in constant-temperature incubation boxes.

(1) Constant-temperature incubation. This uses an automatic temperature control system to keep the temperature inside the box or room within the most suitable temperature range, promoting normal development of the fertilized egg embryos. For small-scale incubation, an electric thermostatic box can be used instead of an incubator. For large-scale incubation, poultry incubators can be modified for use. They can also be specially designed and manufactured. The heat supply is electric power, and the temperature and humidity regulation systems both use automatic control. What holds the Chinese softshell turtle eggs is the incubation sand tray, whose size specifications can be designed and installed to match the space inside the box. During incubation, a layer of wet sandy soil about 4 cm thick is spread on the bottom of the incubation tray. The moisture of the wet sandy soil should be such that it forms a ball when held in the hand and crumbles when shaken with the hand released, and the sand particle diameter should be about 0.5 mm. Then the selected high-quality fertilized eggs are placed neatly in the sand layer, and finally a layer of wet sandy soil 2-3 cm thick is covered over the surface of the Chinese softshell turtle eggs. The incubation tray is placed into the incubation box, the box door is closed tightly, the required temperature and humidity knobs are adjusted, and the power is turned on to enter the incubation state. The temperature for constant-temperature incubation should be controlled at 34°C±0.5°C, and the sand moisture content should preferably be maintained at 8%-12%; the hatching rate can reach 93%. According to the principle of constant-temperature incubation, a device for hatching chicks with a kerosene lamp can also be used for incubating Chinese softshell turtle eggs. Through manual temperature regulation and careful operation, good incubation results can also be achieved. When controlling a kerosene lamp incubator, the temperature must not exceed 37°C, otherwise incubation failure will be caused.

(2) Incubation room incubation. The site for the incubation room should be chosen in a place with high and dry terrain, sheltered from the wind and facing the sun, with good drainage conditions and convenient management. The area should be about 12 sq m, with the orientation facing south from the north, the north wall below 2.5 m high, large glass windows on the east, south, and west sides, and only a small moisture-exhaust window on the north wall. The indoor floor should be hardened with cement and provided with drainage holes. The roof can be covered with transparent film in a saddle shape, or use a glass roof, or a ridged roof. Inside, two shallow pools with walls 20 cm high should be built for temporary rearing of newly hatched juvenile Chinese softshell turtles. The remaining space should be provided with several multi-layer incubation racks so that incubation trays can be placed layer by layer for three-dimensional incubation. The incubation tray is generally 60 cm × 40 cm × 20 cm, with several drainage holes at the bottom. During incubation, a layer of sandy soil 5 cm thick is spread on the bottom of the tray, then the selected high-quality Chinese softshell turtle eggs are placed neatly, and then a layer of wet sand 3-4 cm is covered over the eggs. In one corner of the incubation tray, a small plastic basin is buried, with its rim level with the surface of the sandy soil, and filled with clean water for newly hatched juvenile Chinese softshell turtles to climb onto and splash about, facilitating collection and management. Before the Chinese softshell turtle eggs are placed for incubation, the equipment in the incubation room should be checked and disinfected, rat holes and ant holes should be plugged and filled, and the circuits and lighting facilities should be checked. To ensure the smooth progress of incubation work, an electric stove or coal stove should be kept in the incubation room for supplementary heating during rainy and low-temperature weather. If the room temperature is too high, the windows can be opened to allow air convection to cool it down; or an exhaust fan can be turned on to draw out hot air and moisture, allowing air movement to lower the temperature and humidity. Shading measures can also be used to lower the temperature.

(3) Simple incubation bed open-air incubation. The simple incubation bed is a special sandy soil bed built according to incubation requirements in a place with relatively high terrain, dry conditions, exposure to the sun, and shelter from the wind, specifically for incubating Chinese softshell turtles. The area size can be determined according to the number of Chinese softshell turtle eggs to be incubated. Generally, it is 2 m long and 1 m wide, with the north wall 1.2 m high and the south wall 0.6 m high. It is built around with bricks, with several ventilation holes left in the upper part of the surrounding edge and several drainage holes left at the bottom. The bottom is filled with crushed stone and coarse sand, and the surface layer is spread with 10 cm thick sandy soil. The surface layer should be higher in the north and lower in the south, forming a slope. In one corner on the south side, a water-filled basin is buried, with its rim level with the surface layer of the sand bed. The top of the sand bed is covered with transparent plastic film to achieve the purpose of heat preservation and moisture retention. During incubation, first roll up the plastic film, arrange the fertilized eggs in sections from north to south according to how near or far the laying date is, and bury them in the sandy soil of the sand bed. When placing and burying the eggs, keep a distance of about 1 cm between each egg. After the eggs are placed, cover them with a layer of fine sandy soil 3 cm to 4 cm, insert incubation date markers in the gaps between the eggs, and then cover the plastic film on top tightly, thus entering the incubation period.

During the incubation process, temperature regulation of the incubation bed is mainly carried out by means of the plastic film top, and the heat source is mainly sunlight. At low temperatures, adding electric light bulbs in the space under the cover to supplement heat can also achieve the purpose of heat preservation. In normal weather, for the sake of heat preservation, a layer of straw curtain should be added over the film top cover at night. If hot weather is encountered, a layer of shade net or tree branches should be added over the film top cover during the day for shade, or part of the top cover should be opened to dissipate heat. With this incubation method, juvenile Chinese softshell turtles can generally be seen emerging one after another in about 45 days.

When using an incubation bed for incubation, attention should be paid to preventing damage from rats, snakes, ants, and natural enemies such as birds and beasts, and at the same time attention should be paid to regulating temperature and humidity.