Rapa Nui, better known as Easter Island, is a volcanic island in the southeastern Pacific Ocean famous for its monumental statues. Its remote location makes it one of the most geographically isolated inhabited places on Earth, situated over 3,700 kilometers from the coast of South America. This isolation has fostered a peculiar and fragile ecosystem. The animal life found on Rapa Nui today reflects its remote origins, the impact of human settlement, and the introduction of non-native species.
The Rich Diversity of Marine Life
The oceanic environment surrounding Rapa Nui holds the greatest animal diversity, largely due to the island’s position at a transition zone between tropical and subtropical waters. The volcanic seafloor features corals, arches, and caverns that shelter a unique array of fauna. Approximately 25% of the fish species found in these waters are endemic.
One unique resident is the Easter Island butterflyfish (Chaetodon litus), known locally as the tipi tipi. Other fish commonly observed are moray eels (Enchelycore sp.) and the long-spine porcupinefish (Diodon holocanthus). The waters are also frequented by larger migratory species, including four species of sea turtle, such as the endangered Green sea turtle (Chelonia mydas), dolphins, and whales.
Seabirds rely entirely on the ocean for food while using the land for nesting. Species like the Sooty Tern, Red-tailed Tropicbird (Phaethon rubricauda), and Great Frigatebird (Fregata minor) nest on the main island or its offshore islets. This marine life is protected by the Rapa Nui Marine Protected Area, a conservation zone established to safeguard endemic species.
Surviving Native Terrestrial Species
The native terrestrial fauna of Rapa Nui is notably sparse, resulting from its distant location and historical deforestation that eliminated most of the original habitat. There are no native land mammals, a common characteristic of isolated oceanic islands. The most conspicuous indigenous land animals are a few species of reptile.
Only two species of small terrestrial lizards are currently recorded, both common throughout the Pacific. These include the nocturnal Mourning gecko (Lepidodactylus lugubris) and a small skink (Ablepharus boutoni poecilopleurus). These reptiles may have arrived accidentally, perhaps transported on driftwood or in the canoes of the first Polynesian settlers.
Microscopic invertebrates, such as endemic species of springtails and micro-moths, represent the last remnants of the original native land fauna. These tiny creatures survive in specialized microhabitats, such as native mosses and ferns found within volcanic caves and craters, offering a refuge from non-native insects. The land crab, Calcinus pascuensis, is another endemic invertebrate observed near the water.
The Dominance of Introduced Animals
The modern terrestrial environment of Rapa Nui is overwhelmingly populated by non-native species, introduced over centuries by Polynesian settlers and later by European visitors. The Pacific Rat (Rattus exulans), or kiore, arrived with the first Polynesians and played a significant role in ecological change by consuming the seeds of the large native palm, hindering forest regeneration. Although the Pacific Rat is now locally extinct, it was replaced by European rat species, including the Brown rat (Rattus norvegicus) and the Black rat (Rattus rattus), which remain abundant.
Later introductions brought domestic livestock that now roam freely across large sections of the island, profoundly affecting the open grassland environment. Large populations of horses, cattle, and sheep graze the landscape. These free-ranging animals exert heavy grazing pressure, which prevents the recovery of native vegetation and contributes to soil erosion.
Domestic animals like dogs and cats are also numerous, and their presence impacts the remaining native bird and reptile populations. Poultry, primarily chickens, are a common sight near human settlements.
Extinct Fauna of Rapa Nui
Archaeological evidence, primarily bone fragments found in ancient middens, reveals that the island’s original fauna was far richer than what exists today, particularly concerning birdlife. Before human settlement, the island hosted one of the largest seabird colonies in the Pacific, with an estimated 25 species breeding there. These included petrels, shearwaters (such as the Pink-footed shearwater, Puffinus creatopus), and the Red-footed Booby (Sula sula). Hunting by early settlers and egg predation by the introduced Pacific Rat led to the local extinction of all nesting seabirds on the main island.
The island also supported at least six species of native land birds, all of which are now extinct. Fossil evidence points to the former existence of:
- Two species of rail
- Two parrots
- An owl
- A heron
The loss of their forest habitat, coupled with hunting pressure, resulted in their disappearance before European contact. Historical records suggest that seals, possibly including the Hawaiian Monk Seal, once frequented the shores, but these marine mammals no longer populate the island’s coastline.