Relentless Male Aggression on an Island Threatens Tortoise Extinction

On Golem Grad island in Lake Prespa, Hermann’s tortoises are outnumbered by males 19 to 1, leading to relentless harassment that injures females and drives some off the cliffs; enclosure experiments show even with an escape route, aroused males cause island females to fall, while mainland females avoid exits. Most island females show genital injuries and many are not pregnant, unlike mainland populations where all females are pregnant. Scientists warn this extreme sex bias could trigger an extinction vortex, with projections suggesting the last female could die around 2083.