Native allies: Pine martens helping Ireland’s red squirrels fight back
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In Ireland’s forests, an ecological interaction is helping to restore balance to an ecosystem disrupted by invasive species. The red squirrel (Sciurus vulgaris), once pushed to the brink of local extinction by the introduction of grey squirrels (Sciurus carolinensis), is making a comeback. Key to this resurgence is an unexpected ally, the pine marten (Martes martes), a native predator whose recovery is reshaping Ireland’s woodland ecology.
Grey squirrels were introduced to Ireland in 1911 and quickly became a significant threat to the native red squirrel. Larger and more adaptable, grey squirrels outcompete reds for food and habitat. They also carry squirrelpox virus — which is harmless to them but often lethal to red squirrels. Over the decades, grey squirrels expanded their range, causing a notable decline in red squirrel populations, particularly in areas where the two species overlapped.
Once widespread across Ireland, pine martens faced near extinction due to deforestation and hunting in the 1800s. By the early 20th century, pine martens were locally extinct in many parts of the country, surviving only in isolated pockets in the west and midlands where woodlands remained. Their near disappearance reflected the broader decline of Ireland’s native forests, which once covered the majority of the island but had been reduced to less than 1% of total land area by the early 1900s.
However, their fortunes changed after being granted legal protection under the Wildlife Act of 1976 and following reforestation efforts. Pine marten populations began to recover, particularly in the midlands, west, and parts of Northern Ireland. Counties such as Wicklow, Laois, Offaly, and Galway have seen significant increases in pine marten sightings, and these areas now serve as examples of how their resurgence is influencing ecosystems.
The ecological interaction between pine martens, grey squirrels, and red squirrels is rooted in evolution. Red squirrels co-evolved with predators like pine martens over thousands of years, developing strategies to evade them. Grey squirrels, native to North America, lack these adaptations. Their heavier bodies and slower reflexes make them easier targets for predation.
A study conducted by researchers at NUI Galway and the University of Aberdeen found that red squirrels increase their numbers significantly within five years of pine marten population recovery. The study also highlighted the role of tree structure in this dynamic, where native Irish forests with dense canopies and fine branches favour red squirrels, as these environments are more challenging for pine martens to navigate.
This predator-prey interaction is an example of mesopredator suppression, where the presence of a higher-level predator indirectly benefits another species by controlling the population of a competitor or intermediate predator. In this case, the pine marten’s impact on grey squirrels creates ecological space for red squirrels to thrive.
The recovery of the red squirrel demonstrates how predator-prey dynamics can play a critical role in ecosystem restoration. However, this process is dependent on maintaining healthy habitats for both pine martens and red squirrels. Habitat fragmentation and loss remain ongoing challenges for Ireland’s woodlands, threatening the long-term stability of these populations.
While the pine marten’s return is beneficial for red squirrels, it is not a universal solution to the grey squirrel problem. In urban areas where pine martens are less likely to thrive, grey squirrels continue to dominate. Conservation efforts must therefore include a combination of measures, such as habitat restoration, monitoring of squirrel populations, and community engagement to protect red squirrels in these areas.
The relationship between pine martens, grey squirrels, and red squirrels is a compelling example of how native species can play an active role in restoring ecological balance. It highlights the importance of preserving and protecting native predators, not just for their intrinsic value but also for their ability to influence ecosystems in ways that benefit biodiversity.
Ireland’s red squirrel story is far from over. But with the continued recovery of the pine marten and targeted conservation efforts, there is hope that the reds will regain their foothold across Ireland’s forests. This dynamic relationship demonstrates the complexity of ecological interactions and the resilience of nature when given the chance to heal.
- They’re great at forgetting things. Red squirrels bury nuts to store food for the winter, but they often forget where they’ve hidden them. This forgetfulness benefits the environment, as it helps with tree seed dispersal and forest regeneration.
- They don’t hibernate. Red squirrels stay active throughout the winter. They rely on food stores, such as buried nuts, to survive the colder months. During bad weather, they might spend days sheltering in their dreys (nests), but they don’t truly hibernate.
- A red squirrel’s front teeth never stop growing. This allows them to gnaw on hard nuts and seeds without wearing down their teeth. To maintain healthy teeth, they need to keep chewing regularly.
- They can swim. Although not their favourite activity, red squirrels are capable swimmers. They paddle with their limbs and use their bushy tails for balance. You might occasionally spot them crossing small bodies of water in the wild.
- They’ve been around a long time. Red squirrels have existed in Europe for around 10,000 years, surviving through changing climates and habitats.