As of the 15th of June, 2020, research led by National University of Ireland, Galway has recorded an increase in the native red squirrel population thanks to the growth in abundance to the native carnivore called pine martens in the Irish midlands. There is a significant correlation between the increase of pine martens and decrease of grey squirrels in habitats in the presence of red squirrels because of the grey squirrel's larger size, decreased agility and greater time spent on the ground foraging in comparison to the native red's. This interaction is a classic top-down trophic cascade where the top carnivores dictates the structure of the surrounding ecosystem. These pine martens were studied through a non-invasive, DNA analysis on the pine marten used to study the food consumed. It was discovered wood mice were the primary food source, followed by the grey squirrel and very few red squirrels. The reduction of the invasive American grey squirrel has resulted in an increase in the red squirrel population as grey's transmit a fatal parapox virus that they've built an immunity towards and they also consume all of the green acorns. Red squirrels can only consume green acorns as they cannot digest mature acorns. This will put pressure onto the population of the red squirrels which will prevent them from breeding which will then increase grey squirrel populations further and so worsening the situation.
Queen's University, Belfast (QUB) also performed studies on this trophic cascade and back's this correlation between pine martens and grey squirrels. Studies performed in Northern Ireland (NI) are more important as it's predicted there will no longer be any red squirrels remaining in NI within the next few decades. This study predicts there will be an increase in grey squirrels in urban parks due to the lack of wooded areas in these parks. Joshua Twinning of QUB stated "As the pine maten does not occupy urban areas anywhere within it's European range, it (Pine martens) is not likely to be the sole solution to the invasive grey squirrel".
https://www.thetimes.co.uk/article/first-they-cloned-dolly-the-sheep-now-they-are-targeting-grey-squirrels-xdjzm3rgb
References- Nuigalway.ie. 2020. June - NUI Galway. [online] Available at: <http://www.nuigalway.ie/about-us/news-and-events/news-archive/2020/june/red-squirrels-making-comeback-as-return-of-native-pine-marten-spells-bad-news-for-invasive-grey-squirrel-1.html> [Accessed 16 July 2020].
- Dwyer, S., 2020. Pine Martens Could Be Solution To Saving Red Squirrels In Urban Areas. [online] TheJournal.ie. Available at: <https://www.thejournal.ie/grey-squirrel-and-pine-marten-relationship-5121288-Jun2020/> [Accessed 16 July 2020].
- O'Sullivan, K., 2019. Good Neighbours: How Pine Martens Are Helping Red Squirrels Survive. [online] The Irish Times. Available at: <https://www.irishtimes.com/news/environment/good-neighbours-how-pine-martens-are-helping-red-squirrels-survive-1.3822153> [Accessed 16 July 2020].
