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Chalk Grassland Butterflies

Posted: Wednesday 10th June 2015 by Alice Hunter

Marbled White - Alice Hunter photography

Among the 59 species of butterfly recognised as native to Britain, a number are particularly specialised to the habitat in which they live.

One such butterfly alludes to its preferred ecosystem in its name, the Chalkhill Blue. It is not the only British butterfly which thrives on calcareous soils, the Duke of Burgundy, Adonis Blue and Silver Spotted Skipper are also dependent on this type of grassland. While Marbled White and Dark Green Fritillaries are not completely reliant on chalk, they too seem to proliferate in chalky meadows and hillsides. 

So what is it that makes chalk grassland so special? Strangely enough it is the lack of nutrients in the soil. This allows for a very specific set of plants to grow here and, in turn, the butterflies which they support flourish too. The Chalkhill and Adonis Blues, for example, both favour the horseshoe vetch as a larval food plant which tends only to grow on chalk or limestone soils.

It isn’t just the flowers that are important to the butterflies’ survival though as a number of the Blues have a close association with ants. This also restricts the areas in which these butterflies are found as they tend to prefer south-facing slopes where the grass is very short and the ants are more numerous. There are also other benefits to this position as the ground warms up more during sunny spells and rain water drains away more quickly, so there is less risk of caterpillars succumbing to cold and wet conditions should the weather change.

Here in Hertfordshire and Middlesex we are blessed with pockets of this diverse habitat which are carefully managed to provide a suitable spot for the wildflowers and butterflies to thrive. Neither would do well if the reserves were simply left to their own devices. Instead sheep and cattle are used to graze certain areas to keep the sward short, and teams of trusty volunteers help our staff to cut, rake and carry out general maintenance of these sites.

One such reserve which has seen fantastic results in recent years is Aldbury Nowers near Tring, which has been billed as one of the finest wildflower and butterfly sites in the region. Others include Alpine Meadow near Berkhampstead, Therfield Heath near Royston and Hexton Chalk Pit.

Let us know what butterflies you’ve seen – you could even join in with the Big Butterfly Count which runs from 17th July to 9th August 2015. For more information on how to take part see the Big Butterfly Count website

Article - Alice Kendrick
Picture - Alice Hunter Photography

Read Alice Hunter's latest blog entries.

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