Nature on our doorsteps - Trees tricking and treating nut nibblers

By Rosaleen Dwyer

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures

Because nuts like acorns, beech nuts, chestnuts and hazelnuts are high in fats, creatures like rooks, blue tits, wood mice and squirrels feast on them.  

It therefore takes a little bit of planning by trees to make sure that at least some of their nuts escape the nut nibblers and germinate into young saplings.

Chestnuts will be eaten by woodmice and squirrels compressor

Chestnuts will be eaten by woodmice and squirrels

If trees produced big nut harvests every year, the number of nut predators would swell to the point that very few nuts would get a chance to grow. 

To prevent this, trees synchronise their nut production, producing bumper crops only once every 3-5 years.


Trees do this by first keeping nut production low for a few years. 

This helps to reduce predator numbers. 

Then, when predator numbers are suitably low, the trees produce a bumper crop of nuts in one year.  This is referred to as a ‘mast year’.

Turkish Hazelnuts will be gathered up quickly by grey squirerls compressor

Turkish Hazelnuts are gathered quickly by grey squirrels

Nut eaters do well in a mast year but because predator numbers have been kept low, many of the nuts avoid being eaten and go on to germinate. 

Predator offspring also feed well that year, with many surviving their first winter.

 However, as nut production once again drops low for a few years after a mast year, the number of predators also reduces, allowing the trees to save their energy for their next bumper crop.

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