Ireland is an island nation whose wildlife populations are shaped by its geological history and separation from continental Europe. The country’s fauna has a comparatively low diversity compared to mainland Europe. As the glaciers retreated, rising sea levels isolated Ireland much earlier than Great Britain, meaning fewer species had the opportunity to migrate and colonize the land. Despite this, Ireland’s lush environment, characterized by extensive boglands, forests, and a rugged coastline, supports a unique and often genetically distinct array of animals.
Land-Based Wildlife
Ireland’s terrestrial fauna includes a limited number of native mammals, reflecting the island’s early post-glacial isolation. Among the most recognizable is the Red Deer (Cervus elaphus), the largest wild mammal. The Irish Hare (Lepus timidus hibernicus) is a genetically distinct subspecies of the mountain hare, characterized by a coat that often remains brown year-round, unlike its fully white Arctic relatives.
The island is home to several widespread carnivores, including the Red Fox, the European Badger, and the Eurasian Otter. The Irish Stoat (Mustela erminea hibernica), a unique subspecies, is smaller than those found in Britain and does not reliably develop a white winter coat (ermine) due to Ireland’s milder climate. Ireland’s single native reptile is the Common Lizard (Zootoca vivipara), which is unique for giving birth to live young rather than laying eggs.
Terrestrial amphibians are also present, though in low numbers, with the Common Frog and the Smooth Newt being the most widespread. The Natterjack Toad is confined to a few specific, localized sandy habitats in County Kerry and western County Cork.
Ireland’s Bird Populations
Ireland’s mild, temperate climate and extensive coastline make it a significant destination for both resident and migratory birds. The total number of bird species recorded is high, although the number of breeding species is smaller due to the island’s isolation. Resident songbirds like the European Robin and Blackbird are common sights in gardens and woodlands across the country.
The island’s western cliffs and offshore islands are internationally recognized as breeding grounds for vast colonies of seabirds. Species like the Atlantic Puffin, Northern Gannet, and Common Guillemot nest in enormous numbers on sheer rock faces. Northern Gannets are known for their spectacular high-speed dives into the sea to catch fish.
Ireland also serves as a crucial stopover point and wintering ground for numerous migratory species. Waders and wildfowl, including half the world’s population of the Greenland race of Greater White-fronted Geese, are attracted by the mild conditions. Raptors such as the Peregrine Falcon are also resident, often nesting on coastal cliffs.
Marine and Aquatic Ecosystems
The waters surrounding Ireland, influenced by the warm North Atlantic Current, support a diverse and abundant marine fauna. Ireland was designated as Europe’s first whale and dolphin sanctuary, reflecting the importance of its seas for cetaceans. Around 24 species of whales, dolphins, and porpoises have been recorded in Irish waters.
The most frequently sighted species include the Common Dolphin and Harbour Porpoise, while larger visitors like Humpback and Fin Whales are seasonally present, often feeding off the south coast. The Basking Shark, the world’s second-largest fish, is a regular visitor to Irish coastal waters during the summer months, feeding exclusively on plankton. These cold, temperate seas are also home to two species of seals, the Grey Seal and the smaller Harbour Seal, which breed in colonies along the coast.
Freshwater ecosystems, including rivers and loughs, host native fish species like Atlantic Salmon, Brown Trout, and Arctic Char. The European Eel and the Pollan, a rare freshwater herring, are also native inhabitants of the island’s inland waters.
Notable Ecological Differences
Ireland’s unique faunal composition is best understood by examining the species that are conspicuously absent, a direct consequence of its early post-glacial history. The most famous example is the complete lack of native snakes, a phenomenon due to geography, not legend. As the last Ice Age ended, a temporary land bridge allowed some animals to cross from continental Europe via Britain.
However, the land bridge connecting Ireland to Britain submerged approximately 8,500 years ago, earlier than the one connecting Britain to Europe. This earlier isolation meant that many species, including all snakes and several mammals like voles and moles, did not have enough time to colonize Ireland.
The island’s relative scarcity of large terrestrial mammals is also notable; species such as the European beaver, wild boar, and certain large predators that were present in Britain failed to reach Ireland before the sea level rose. This resulted in a terrestrial mammal fauna of only 26 native species, significantly lower than the diversity found on the European mainland. The unique genetic characteristics found in several Irish species, like the Irish Hare and Irish Stoat, are a testament to this long period of independent evolution.