There are two main seasons in Astrochelys radiata habitat, which differ primarily in day-night temperature gradient and rainfall.
A Malagasy summer covers the months of September to May. During this time it is very hot and mostly dry. Although the rainy season lasts from November to March, rainfall is rare in some areas. Occasionally, however, very heavy and abundant rains may suddenly occur in parched zones. Temperatures and humidity always remain in the tropical range in summer, both during the day and at night.
Winter in Madagascar lasts from June to August. Temperatures are somewhat more moderate during the day, but this season is also characterized by extreme drought. Seasonally, cool winds blow especially in the southern range of Astrochelys radiata, and nighttime temperatures of less than 10°C may occur. The day-night temperature gradient can exceed 20°C in winter. The animals then only have the opportunity to warm up again in the sun during the day. During long periods of cool temperatures or extreme drought, the ray-turtles retreat to protected hiding places to conserve energy and resources.
For comparison, seasonal average climate data from Tulear, Madagascar (after Müller 1996):
Temperatures in the indoor area during the cold season
In our latitudes, the necessary climate factors can only be realized in winter in closed systems indoors, well-insulated conservatories or greenhouses. In order to recreate a Madagascan summer during the European winter in an indoor environment, a high, technical effort is necessary. To save energy, we have lined the walls of our turtle interior with thick cold house elements that have a high tolerance to heat and humidity. Due to the good insulation, the temperatures are kept in the desired range for a long time, even without heating during the night. On the floor, partial floor heating is incorporated under the tiles, which provides an even, constant room temperature on cold winter days. Two large skylights, through which natural daylight falls, further warm the interior. Several, large HQI spotlights 400W as well as some Lucky Reptile Bright Sun Desert spotlights 150 Watt, provide additional light and warmth.
During the cold season (October to March), the following temperatures prevail in the turtle indoor facility:
Temperatures in the shelters during the warm season
A Malagasy winter is roughly equivalent to a better Central European summer in terms of temperatures, but with significantly more hours of sunshine and no precipitation. This means that Radiated Tortoises in the European summer, with good weather conditions as often as possible should be kept in the open air. Cloudy, rainy and cooler days must be bridged and compensated for with the help of heated greenhouses or cold frames. Radiated Tortoises show high tolerance to cool, nighttime temperatures in a protected, dry environment (e.g., greenhouse). However, during the European summer, meticulous care must be taken to avoid exposing the animals to cold soil moisture. Low temperatures in combination with continuous cold precipitation, as we know it in Europe, do not occur in the southwest of Madagascar! The organism of Radiated Tortoises is therefore not prepared for this weather constellation and reacts with irritation and stress. On the one hand, cool rain signals the animals to become active and drink, on the other hand, temperatures are too low to get up to operating temperature. These contraindicated impulses have an unfavorable effect on health. Excessive intake of cold rainwater in a cold environment also has an unfavorable effect on metabolism. Heat storms in summer are an exception. These should definitely be allowed to be experienced by the animals during the day.
During the warm season (March to October), the following temperatures have proven to be effective in the shelters:
In temperature management, it is important to keep in mind that Astrochelys radiata also knows seasons in its natural habitat. One of the most common husbandry mistakes in this context is that the animals are kept at relatively constant, high temperatures and too low humidity all year round. Especially for the reproduction and fertility of the females, offering seasons seems to be important. We suspect that the seasonal light and temperature differences influence the hormonal egg maturation cycle.
FAQ on the topic of temperature
Radiated tortoises always belong in an outdoor enclosure during the warm season, in sunny and dry weather! Provided that the sun is shining, the outdoor enclosure is located on a southern exposure and the animals can warm up in a heated cold frame or greenhouse, radiated tortoises are allowed into the outdoor enclosure already from 15°C outside temperature. Only during longer periods of cold and wet weather and low temperatures should the radiated tortoises be kept exclusively in heated, enclosed shelters or in the indoor enclosure.
If the sun is shining, we let our animals already at the beginning of March for a few hours in the outdoor enclosure, so that they can refuel extensively UV light and fresh air. Over midday it may then have mild temperatures of 15 to 20°C. Sometimes there is still some snow in the outdoor enclosure, but this does not seem to bother the animals. At the latest from 16 o'clock all animals must be again in the heated turtle house. The night is always spent in the transitional periods in a heated and protected indoor!
Warm and dry summers our radiated tortoises are allowed to spend day and night in the outdoor enclosure. In midsummer, all lights and heating elements in the cold frames and in the indoor enclosure remain switched off. The roof flaps of the cold frames for the hatchlings are then always open to prevent overheating. In summers with tropical nights, we also close the entrance to the indoor enclosure for the adult turtles, so that they can spend the night under bushes in the outdoor enclosure as close to nature as possible.
In order to benefit optimally from the natural sunlight, we also try to allow the stay in the outdoor enclosure as long as possible in autumn. If the weather remains sunny and dry, ray turtles can make forays into the outdoor enclosure during the day until the end of October. However, the animals should then always spend the nights in heated and locked shelters. At the latest when the power of the sun decreases, the outside temperatures drop below 15°C and there are persistent wet and cold weather conditions, radiated tortoises must be brought into the heated winter quarters until the next spring.
FAQ "...Do radiated tortoises also hold a cold torpor? Can I overwinter them together with my Greek tortoises?"
Attention: Radiated tortoises originate from a subtropical climate zone. Their body has therefore no physical adaptation and prerequisite to survive a seasonal cold drought, such as European tortoises hold. Attempting to hibernate a radiated tortoise will end fatally for the animal! Please inform yourself before the acquisition in detail about the needs and keeping conditions of these animals!