Around 1,000 Hermann's tortoises live on the island - an exceptionally dense and seemingly prosperous population. However, behind these numbers lies a serious problem: the sex structure is dramatically distorted. For every adult female there are as many as 19 males, an extreme disproportion with far-reaching consequences. This imbalance results in pronounced sexual aggression among males, who not infrequently attempt to “mate” with one another as well. Females are subjected to constant harassment, stress, and physical injuries. In their attempts to escape the aggression, some females end up falling over the island’s steep cliffs - into certain death.
The true causes, or combination of factors, that have led to this situation remain unclear. Nevertheless, if this population trend continues, models suggest that the last female tortoise on Golem Grad could disappear by 2083. This issue is inextricably linked to another enigma: how these tortoises came to be on the island in the first place, given that they are not capable of swimming across the lake.
One theory proposes that the tortoises were brought by humans, and in an unequal sex ratio. They are capable of living for around a century under favorable conditions, and the oldest males on Golem Grad bear engraved numbers on the underside of their shells - perhaps an indicator supporting this theory? Still, definitive answers are lacking.
What is certain is that the tortoises of Golem Grad will continue to attract the attention of both the scientific community and the global public.
Link to the The New York Times article: https://www.nytimes.com/2026/02/14/science/tortoises-island-sex-cliff.html
Link to Dragan Arsovski’s new scientific paper: https://onlinelibrary.wiley.com/doi/10.1111/ele.70296
