Biodiversity Day in the Vis Archipelago: Life on Black Offshore Rocks

On the occasion of International Biodiversity Day and Nature Protection Day in Croatia, the Vis Archipelago Geopark highlights one of the seemingly small, yet exceptionally interesting features of its island fauna – the black lizards inhabiting the offshore islands of Jabuka and Brusnik.

These are lizards from the group of karst lizards, whose individual island populations in the central Adriatic region have developed an extremely dark, almost black coloration. In professional and popular scientific literature, such a phenomenon is often associated with melanism, i.e., an increased amount of dark pigment in the skin. In island lizard populations, such characteristics are particularly interesting as they indicate a long-term adaptation to life in isolated and specific environmental conditions.

Jabuka and Brusnik are among the most unique islands of the Vis Archipelago. Unlike most Croatian islands, which are primarily composed of limestone, Jabuka and Brusnik are associated with magmatic, or volcanic, rocks, giving them exceptional geological value. Both islands are protected as geological natural monuments and are also located within the broader area of the UNESCO Global Geopark Vis Archipelago.

Precisely such a habitat shapes the life that survives on them. Offshore islands are exposed to intense sun, wind, sea spray, scarcity of soil, and very limited vegetation. In such places, there is little shelter, food, or water, so life develops under conditions of constant exposure. The black lizards of Jabuka and Brusnik are therefore not just an interesting detail of the island fauna, but a valuable example of how isolation, geology, and climate can influence the appearance and survival of species.

Jabuka's uniqueness is further emphasized by its location and composition. This uninhabited, steep offshore islet is located west of Vis, and its dark volcanic rock contains magnetite, which traditionally causes disturbances in magnetic compasses near the island. Only species highly adapted to extreme conditions can survive in such an inaccessible and barren environment.

Brusnik, though smaller and lower, is also an exceptional example of an offshore island habitat. Its landscape consists of dark rocks, large stone pebbles, and very sparse vegetation, and the black lizard is often cited as one of its most famous living peculiarities.

The importance of these lizards lies not only in their rarity or unusual color. They remind us that biodiversity is not solely comprised of large, easily recognizable species and attractive natural phenomena. It often manifests in small, local, and sensitive populations living on rock edges, in stone crevices, and on islands rarely visited by humans.

That is precisely why the offshore islands of the Vis Archipelago are valuable natural laboratories. They clearly demonstrate the connection between geology, climate, isolation, and the living world. The black lizards of Jabuka and Brusnik are a small but powerful reminder that the natural value of an area is measured not only by its size but also by the uniqueness of the life that has evolved there.

On International Biodiversity Day and Nature Protection Day in Croatia, they remind us of the importance of preserving even the smallest habitats – because it is often within them that nature's most unique stories are hidden.