However, when fires occur every 30 years (a frequency similar to the natural cycle in Mediterranean environments), medium-large populations of spur-thighed tortoises will not become extinct, according to models designed by the researchers. "Above this limit, the likelihood of extinction increases exponentially", the experts warn.
None of the youngest tortoises were able to survive the passage of fire in any kind of terrain, because of the type of shelter they choose below vegetation or in very shallow holes. They are also less able to withstand high temperatures, since their shells are not yet ossified.
Danger increases in spring
Although the fire reduced dozens of animals to ashes, the scientists found live individuals surviving in shelters they dig for themselves to sit out the periods of greatest temperature stress, in winter and summer.
The animals' behaviour changes in other seasons, however, and their activity levels increase. "In spring, the tortoises hide under bushes, meaning that, if a fire occurred at that time, they would all be wiped out", says Sanz-Aguilar.
The spur-thighed tortoise is found throughout Europe, Africa and Asia. In the European Union, the most numerous populations are found in the south east of Spain, between Murcia and Almeria, where they range over an area of 2,600 km2. "This is a typically Mediterranean species, and the natural landscapes of this zone suffer from certain kinds of fire, which recur infrequently", the researcher explains.
The International Union for the Conservation of Nature (IUCN) has classified this tortoise as 'vulnerable', and at risk of extinction over the medium term. In Spain, it is classified as 'endangered' on the Red Book of the Amphibians and Reptiles of Spain.
|Contact: SINC Team|
FECYT - Spanish Foundation for Science and Technology