Invasive long-eared mammals, or how rabbits and hares are changing ecosystems

Small, fluffy, with large ears and a gentle look, rabbits and hares seem like the last animals we would suspect of devastating nature. Meanwhile, research shows that in favorable conditions, especially outside their natural range, they can become dangerous invasive species and significantly transform ecosystems.

Not every long-eared mammal is invasive

Not every rabbit and not every hare is an invasive species. The problem arises when an animal ends up outside its natural range and begins to reproduce rapidly. The best example is the European rabbit (Oryctolagus cuniculus), which has been listed by IUCN/ISSG among the 100 of the world’s worst invasive alien species.

The reason is simple – after introduction, the rabbit very efficiently colonizes new areas and strongly affects the environment. It grazes vegetation, triggering an entire chain of changes. Plant cover becomes poorer, soil is exposed, erosion occurs more easily, and habitats become less stable. As a result, not only plants suffer, but also animals dependent on specific types of vegetation, especially birds and invertebrates.

This is why the European rabbit is described in scientific literature as a species with exceptionally well-documented, severe environmental and economic impacts. It is not only about damage to crops. In many places, its presence leads to lasting changes in the structure of entire habitats.

Why rabbits can be so dangerous

This is most evident on islands, where ecosystems are particularly sensitive to alien species. Research from the Kerguelen Islands showed that after the introduction of rabbits, significant changes occurred in plant communities. When the animals were removed, plant species richness began to recover. This is one of the strongest pieces of evidence that the rabbit is not only a troublesome herbivore, but also a real driver of environmental transformation.

Similar conclusions were drawn from studies on the islands of the Aegean Sea. Where rabbits were still present, scientists recorded more exposed soil, fewer specialized and endemic plant species, and poorer arthropod communities. It is not only the grazing that matters, but also the digging of burrows and tunnels, which loosens the soil and accelerates its removal by wind. In the dry, hot Mediterranean climate, such a process can very quickly intensify habitat degradation.

The impact of rabbits, however, is not limited to vegetation alone. On islands, their presence can also indirectly harm birds and other native animals. On the one hand, grazing reduces habitat cover and worsens breeding conditions, and on the other, a growing rabbit population becomes an easily accessible prey for predators, which can increase their numbers and pressure on other species.

Australia – when an invasion gets out of control

An even larger scale of the problem can be seen in Australia. Distribution models show that the European rabbit can occupy about two-thirds of the continent. It is favored by local temperatures, access to water, and soils suitable for burrowing.

The consequences are well known – consumption of seeds and seedlings, hindered regeneration of shrubs and trees, land degradation, and pressure on native fauna. Importantly, controlling rabbits is extremely difficult. Even after control measures, populations can quickly recover, which is why effective management of the invasion requires combining several methods and long-term monitoring.

Interestingly, the latest genomic studies show that the success of rabbits in Australia was not determined solely by the scale of introduction. A key role was played by a single lineage of wild rabbits, better adapted to environmental conditions than earlier, less successful introductions. This shows that the success of an invasion depends not only on the place a species reaches, but also on the traits of the individuals.

The European hare can also cause harm

In the case of the European hare (Lepus europaeus), the problem is usually more local. After introduction outside its natural range, this species can compete with native lagomorphs for food and habitats, and in some regions it is also indicated as a potential source of additional pressure related to parasites and diseases.

The most frequently cited example is Ireland. There, the introduced European hare has been considered a threat to the native Irish hare primarily due to competition and hybridization, that is, interbreeding with the local species. This is a particularly serious problem, because what is at stake is not only population size, but also the preservation of its genetic distinctiveness.

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main photo: Guerrero De la Luz/Pexels