Except during the rainy season, humidity in Astrochelys radiata habitat is not produced by precipitation or evaporation of soil moisture, but mainly by sublimation of moist air. Specifically, seawater evaporates due to intense solar radiation on the southwest coast of Madagascar. This moist air reaches the coastal region as well as the interior through air currents. Due to the day-night temperature gradient or the gradient of air and ground temperature, the humid air sublimates in the form of fog in the early morning on the vegetation and also on the turtle shell. The soil is therefore only briefly moist on the surface in the morning and dries again quickly with increasing sunlight.

A common mistake in this context is therefore the excessive moistening of unsuitable substrates such as bark, mulch, peat, etc. in closed and poorly ventilated containers (e.g. glass terrariums). Heat sources cause the wetness stored in the substrate to evaporate and condense again on the terrarium ceiling and return to the substrate by dripping off. This creates a more or less closed circuit in which bacteria and spores begin to circulate. These can then be absorbed through the tortoise's respiration and make the animals seriously ill. It is therefore better to keep the animals in open tubs, in air-conditioned and well-ventilated rooms. If this is not possible, care should be taken to ensure good ventilation when keeping young animals in a terrarium. Also the substarat should not be moistened excessively, but every morning regularly (possibly also in the evening) the turtle shell should be sprayed gently. A timer controlled humidifier or ultrasonic humidifier can also help to keep the humidity in the air high. Waterlogging should be avoided at all costs.

During the European winter, we simulate a Madagascan summer for our animals in the indoor facility. This includes a humidity of about 70%-80%. We achieve this relatively high humidity without any problems by lush planting in the indoor area with hibiscus, cacti, mallows, succulents, etc.. These potted plants, which stand on the ground but are not accessible to the turtles, are watered regularly and store moisture in their substrate, which is released into the room in advance. Another advantage of indoor planting with food plants is that varied fresh food is available even in the cold season. In addition, the substrate of the oviposition site is also regularly moistened. Underneath there is a floor heating, which ensures a uniform and extensive evaporation.

Twice a week, the entire floor of the indoor enclosure is hosed down with warm water and cleaned. Due to the gentle slope of the floor, the water flows off into a shaft. This always leaves some residual water, which dries quickly by means of the floor heating and also evaporates into the room. However, care should be taken to ensure that the animals are not exposed to waterlogging and do not lie wet at night. Cool temperatures in conjunction with moisture is bad for the animals.

Increasing the humidity always has an extremely stimulating effect on our animals and usually triggers spontaneous mating. Especially the males react very much to the increase in humidity. Basically, this method can be used to artificially animate ray turtles to mate at any time. Also before, during and after warm summer thunderstorms, due to the increased humidity, increased mating activities can be observed.

Humidity also plays an essential role in rearing. If the humidity is too low over a longer period of time, juveniles of Astrochelys radiata tend to develop humps of the carapace, independent of the diet, because the fine, white and strongly perfused growth sutures between the shield plates dry out and cause a growth disturbance. In the wild, juveniles reside mainly under decaying foliage and other dead plant matter. There, even during drought, a relatively temperate microclimate prevails that favors growth. Our hatchlings like to huddle under leaves up to halfway into the soil substrate and only come out of their hiding places to eat, drink and warm up. They especially like to gather in groups under pieces of bark, where humidity and warmth are well maintained near the bottom in an ideal ratio. A constant high humidity with different heat zones is difficult to achieve in closed glass terrariums. Therefore, we raise our hatchlings in large, open tubs in the turtle house.