Butterfly conservation on the Holnicote Estate

Heath fritillary perched on fern leaf

The rangers at Holnicote Estate have been managing the habitat for a rare species of butterfly, the heath fritillary for 30 years. The butterfly is a rare species only found in a few places in the UK.

Thirty years of the heath fritillary

The Heath Fritillary is arguably one of, if not the rarest butterfly in the UK when you consider its limited geographic distribution and has one of its main strongholds on Exmoor, with most coloniesare located on the Holnicote Estate.

The Heath Fritillary (Melitaea athalia) has seen its distribution shrink by 68% in the period from 1976 to 2014. As a result the Heath Fritillary is a species of high conservation importance: it is listed in Schedule 5 of the 1981 Wildlife and Countryside Act and is identified as a priority species in the UK governments Biodiversity Action Plan (BAP).

With it being so rare it is important that its numbers are checked every year, to enable effective conservation measures to be put in place to try and avoid any further declines. Monitoring of the Exmoor Heath Fritillary populations has been carried out since 1984 and is co-ordinated by our partners, Butterfly Conservation.

heath fritillary larva
Heath fritillary larva
heath fritillary larva

Managing the land

After observing such a dramatic decline, it was apparent that there was little option other than direct and robust habitat management to try and restore the fortunes of the Heath Fritillary on Exmoor. 

Key to the butterfly’s recovery would be the abundance of Cow-wheat which had since been shaded out by competing vegetation and bracken litter due to under-management of their favoured sites.

Cow-wheat is an annual plant, semi-parasitic on bilberry and the key larval food plant for the Exmoor heath fritillaries.

Positive results

Since 2005 the Heath Fritillary has continued not only to increase in numbers at key sites but also re-colonised some historic sites, particularly in the combes on the lower slopes on the northern side of Dunkery Beacon.

During 2020, not only have good numbers been recorded at their key sites but there has also been widespread dispersal of individuals searching out new habitat.

Modern technology lends a helping hand

The Bromford flailbot has quickly become a valuable addition to the Holnicote Estate. This remote-controlled flail mower has allowed the rangers to take a different approach to the management of some of our most valuable sites, from orchards to heathlands.

Flailbot can access remote sites which are hard get to with vehicles and traditional machines. Many of these places would be unsafe to use a tractor on, whereas the flailbot can be used when working on steep slopes and coastal areas with a reduced risk to safety.

On Holnicote Estate our health fritillary population is found on steep slopes in woodland edge habitat. The rangers use flailbot to manage their habitat by breaking up the vegetation, cutting back scrub which allows light in for common cow-wheat, the main food source for the caterpillars.

Flailbot at work on the Holnicote Estate on Exmoor
Flailbot at work
Flailbot at work on the Holnicote Estate on Exmoor