Assisting Aestivation

Around this time of year, as the swamps are filling up, Western Swamp Tortoises are leaving their summer hideout and returning to the water to feed. Over the summer the tortoises remained inactive by aestivating, but what does this mean?

Throughout winter and spring the tortoises need to fatten up on their favourite aquatic foods. During November, as the swamps are drying up, so is the supply of food for the tortoises! To avoid the problem of having no food, swamp tortoises leave the swamps to aestivate, which means they remain dormant over summer and autumn. Depending on their environment, the tortoises may choose to aestivate under leaf litter, in cracks in the clay or in holes dug by other animals (such as rabbit burrows).

Aestivation is very similar to hibernation during winter. The tortoises spend the summer essentially sleeping and moving very little. They rely on the fat stores they built up over spring to provide them with all of their energy, and so will lose weight over the summer.

Tortoises that remained hidden in the soil over the summer will usually move up into leaf litter or hide under shrubs for the end of autumn. They will remain here until there has been enough rain to begin filling up the swamps and there is enough food for them again. Here they can start eating and the cycle begins all over again.

At Twin Swamps and Mogumber Nature Reserves the tortoises will often aestivate under leaf litter or vegetation, which provide little protection from fire. ‘Aestivation tunnels’ at these reserves provide extra aestivation sites and protect the tortoises within them from fire.

These aestivation tunnels are simply a semi-circular piece of PVC pipe around 1 m long that is dug into the ground on a gentle slope. Tortoises at Perth Zoo are able to aestivate in these tunnels each summer, and it is hoped this will improve survival on release. FoWST and DEC have plans to install more tunnels later in the year and we hope that you will join us in this important activity.

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