Overheating Dangers
by Nadine Highfield

We have already had several weeks of very warm summer weather this year, and though a dry sunny day is normally welcomed by tortoise and turtle keepers, higher temperatures can also present overheating dangers. We all know about the danger of leaving dogs in hot cars - but we often fail to realise that similar dangers face tortoises in captivity.

Tortoises kept overnight in green houses are at particular risk. Once the sun comes up, the temperature within a green house rises very quickly, and will far exceed the outdoor temperature. A tortoise can overheat and perish in minutes.

Preventing overheating in greenhouses:

Greenhouses need adequate ventilation when being used for tortoises in warm weather. Test the interior temperatures in different conditions to make sure your tortoises are safe with the ventilation provided.

If keeping tortoises in a green house overnight, open up the greenhouse as soon as the sun comes up and give the tortoises access to their outdoor area. The interior temperature in greenhouses can rise to dangerous levels very quickly - so quickly, in fact, that a tortoise may not have the time to react and reach the safety of a shelter, even if one is provided.

Provide a depth of substrate within the greenhouse where the tortoise can burrow. The temperature, even a few inches below the surface, will be cooler and help to prevent overheating.

Provide shady areas in the greenhouse where a tortoise can retreat. Areas with vegetation and hides will allow a tortoise easy access to shade and shelter if the temperature rises.

NEVER keep tortoises on tabletop units in a greenhouse. Any units not in contact with the ground will reach critically high temperatures very quickly, and provide no means of shelter or escape. It is much safer to have tortoises at ground level where they have substrate to burrow into and can escape the heat.

How to Prevent Overheating

Like many other reptiles, the body temperature of a tortoise is determined not only by the heat of the sun, but is also affected by the temperature of the surface it is in contact with. A tortoise will bask to raise its body temperature, but when the temperature begins to rise above that which it prefers, the tortoise will begin to search for options to keep from overheating.

In the wild, a tortoise will escape from excessive heat by finding a shady spot, burying down or by using scrapes and burrows. The precise way they choose to shelter will depend on their habitat and on the severity and duration of heat. Tortoises (even those of the same species), may also have different preferences, so tortoises kept in captivity should be given various options in their outdoor areas.

Vegetation is often used by tortoises for shade and shelter, and should always be included in a tortoise pen. Rosemary, lavender, and other plants found in scrubby Mediterranean habitats will create a more naturalistic tortoise area, as well as provide needed shade. Pampas grass, found in the African habitat of Savannah species, such as Leopard, Star and Sulcata tortoises can be planted in larger grazing areas, and the tortoises will shelter from the sun underneath the overhanging grass. These grasses can grow to a very large size and will continue to spread outwards, but can be contained if an underground perimeter is placed to keep the roots within a chosen area. For smaller areas, or juvenile pens, more compact grass species can provide the same benefits.

Scrapes and burrows are commonly used by arid species, and help them to avoid extreme temperature fluctuations and retain body fluids during periods of excessive heat. If you live in the UK, or any climate that has more rain and humidity than your tortoise would experience in the wild, you must ensure that the tortoise area has good drainage and dries quickly after a rain. A tortoise cannot create a proper scrape or burrow in wet earth, and sitting on or burying down in wet substrate are a common cause of shell infections. If you have a Mediterranean tortoise or other arid species, the first step is to provide an area with dry and sandy substrate, sloped areas, and good places to burrow in or under.

Tortoise Scrape
Scrapes protect the head and front section of the tortoise. They also offer a degree of protection against predators. Although the carapace is exposed, the front legs and head are below the surface, which helps prevent fluid loss from respiratory evaporation. A tortoise may dig a scrape in a more exposed spot, allowing some of the sun’s radiant heat to fall on its shell. Other scrapes may be partially or fully covered by overhanging grass or vegetation, offering both shade and the additional benefit of camouflage, which prevents them from being seen by predators. Tortoises will dig scrapes at the base of plants, rocks or other stationary objects, provided they can excavate a large enough opening in the substrate. If you give them these areas, they will dig one or more scrapes in their outdoor habitat.

Burrows are commonly used by tortoises, and allow them to fully retreat from extreme temperatures. Excessive heat combined with a lack of rain results in a scarcity of edible vegetation, and wild tortoises in arid habitats will estivate during these periods. Burrows, which can be several feet under the ground, offer increased temperature stability and excellent protection from predators. Tortoise will dig burrows on slopes where the roots of vegetation hold the soil together. If you create an area like this in your outdoor enclosure, and a tortoise finds it acceptable, it may dig a burrow.

Custom designed hides and burrows are another option for providing shelter and shade in a tortoise pen, and can be easily constructed. Just as light colour cars stay cooler inside than darker vehicles, the exterior colour of a tortoise hut will have an effect on the internal temperature. The tortoise hut pictured above has been painted white so that the heat of the sun will be reflected rather than absorbed. It has also been sheltered in vegetation. By placing the shelter on a depth of substrate, tortoises will also have the option of burying down to the cooler area below the surface.

Protecting small tortoises from overheating.

Juvenile tortoises are extremely vulnerable when exposed to high temperatures. Due to their smaller body mass they will overheat much more quickly than a large tortoise.

If you are keeping juveniles in trays and tortoise tables, never place them in direct sunlight as critical overheating can occur very quickly - even if they are in contact with the ground. It is much safer to provide them with a separate, secure outdoor pen with natural substrate and adequate anti-predator protection. The increased air circulation outdoors also helps to provide additional cooling.

Tortoises or turtles kept in vivariums are also in extreme danger if these units are exposed to direct sunlight. Tortoises can quickly overheat indoors if exposed to strong sunlight through a window or conservatory ceiling.

Sick, blind, weak or injured tortoises should never be placed in direct sunlight in hot weather as they may not be able to move to a cooler spot. These tortoises can reach critical temperatures very quickly and can die as a result.

Protecting Aquatic Turtles

Turtles are also at risk of overheating in hot, summer weather, particularly if they are kept in small, shallow ponds.

In the wild, aquatic turtles live in ponds, steams and other bodies of water that have adequate depth to prevent overheating. If a pond becomes too shallow in summer, certain species may bury down into the mud until the rains come. Others, like sliders, will migrate to a deeper pond. But, all turtles must be given options to escape from excessive heat.

To protect turtles from overheating you need to ensure that their water remains in a suitable temperature range, and with a temperature gradient that allows them to thermoregulate.

Have an adequate depth of water in the pond.
Natural ponds have a depth and volume of water that keeps the water temperature more stable, and provides a temperature gradient. Shallow water and small ponds will overheat much more quickly.

Insulate the outside of the pond. In-ground ponds are less likely to overheat because they have the moderating affect of the cooler earth under them. Above ground ponds are more likely to overheat, so they need to be insulated by surrounding them with sand bags and enclosing them with a wall or decking boards.

Add vegetation to provide shade. Taller vegetation at the edge of a pond will help create a shady area, and floating aquatic plants will shade the surface, keeping the water below cooler.

Provide access to sun and shade. In the wild, turtles will move from one basking spot to another as they follow the sun during the day. When designing a turtle pond look at where the sun falls and ensure that one part of the pond is always in shade when the sun is overhead. This will allow the turtle to bask when it needs to raise its body temperature, and also give it a place to retreat to if certain areas become too warm. Adequate shade will also provide a needed temperature gradient and prevent the overall temperature of the pond from becoming too high.

Tortoises and turtles need shade and shelter to protect them from extreme temperatures. By providing them with the same protection from the heat and the sun that they would have in the wild, you can ensure that they can safely enjoy the summer.