Keep your friends close and your enemies closer, as the famous saying goes.

In nature, your worst enemies can sometimes be your best friends. An example of this is from the UK where the Eurasian red squirrel benefit from marten making a comeback.

In the UK, the red squirrel has been in constant retreat and decreased in numbers in recent years due to the invasive North American grey squirrel taking over more and more.

The gray squirrel was imported from North America and carries a deadly virus that has stricken the common red squirrel very hard.

But in places where the squirrel eating marten has been reintroduced after being hunted hard, the gray squirrels suffer the most, according to a new study that has been done in Scotland.

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The European pine marten (Martes martes)

So despite the fact that the marten is actually the enemy of the red squirrel, they look to benefit from the marten being reintroduced and prefer its gray relatives as food.

“Our study has confirmed that exposure to pine martens has a strong negative effect on grey squirrel populations, whereas the opposite effect was observed in red squirrel populations who actually benefitted from exposure to martens.”

– Emma Sheehy of the University of Aberdeen, Scotland


Emma Sheehy et al. The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing gray squirrel populations. Proceedings of the Royal Society B. March 7, 2018. DOI: 10.1098 / rspb.2017.2603