Self-destructive behaviour among Hermann’s tortoises on a Macedonian island is leading to ‘demographic suicide’

Golem Grad island in North Macedonia is full of Hermann's tortoises. However, demographic projections suggest the last female could be wiped out by 2083. A female (pictured) that had fallen down a sheer drop of more than 20 metres. Fourni par l'auteur

On the strictly protected island of Golem Grad in North Macedonia, the tortoises are destroying their own population. During prolonged courtship, aggressive males are exhausting the females and frequently pushing them off the cliffs. Consequently, there are now one hundred males for every female capable of laying eggs. This is the only known example of demographic suicide in the wild to date.

Under favourable, stable and protected environments, large animal populations have no reason to die out. This should not happen unless a catastrophe, such as a devastating fire or the destruction of their habitat, or over-exploitation, wipes out all individuals or weakens the population, making it vulnerable to disease and other disturbances and hazards.