Heath fritillary butterfly fights back against the odds

Times

6 hours ago

Against a backdrop of butterfly decline in the UK, one species is bucking the trend.
The heath fritillary butterfly, nicknamed the woodman's follower, is undergoing a significant rise in numbers and range on Exmoor, conservationists revealed on Wednesday.
Since 1976, the heath fritillary has seen a 96 per cent decline in its distribution, and is now only found in four areas of the UK.
However, more than 1,000 of the butterflies were recorded during surveys in May and June across Exmoor, compared to 600 at the same time last year. The increase has been attributed to habitat management by the National Trust and Butterfly Conservation.
The charities' efforts include using Devon Red cows to selectively graze land, removing bracken and cutting glades at the woodland's edge. The butterfly's comeback has been remarkable in places, including one site on Exmoor, rising from just four sighted last year to 186 this year.
A particularly sunny spring has caused the heath fritillary to emerge two to three weeks earlier than usual. However, this has led to concerns that climate variability could affect the butterfly's life cycle, if wet weather arrives before the peak of the flight period.
Basil Stow, the area ranger at the National Trust Holnicote Estate, an area of 12,500 acres within Exmoor National Park, said of the increase: 'It's a real testament to the dedication of our teams, volunteers and partners who have spent a huge amount of time since the 1980s understanding and caring for the needs of this vulnerable species.'
Jenny Plackett, the south-west England conservation manager at Butterfly Conservation, said: 'The heath fritillary is generally very sedentary, so this kind of expansion is highly unusual and suggests that recent habitat management is working. We're hopeful these populations will establish and extend their range across the estate.'
The heath fritillary and the high brown fritillary are among the UK's rarest butterflies and rely on carefully managed habitats.
While the high brown favours woodland clearings where it lays eggs on dead bracken or leaves near to violets, the smaller heath fritillary thrives in moorland and coppiced woodland where its caterpillars feed exclusively on common cow-wheat.
The heath fritillary remains restricted to Exmoor National Park, the Blean Woods in Kent, the Tamar Valley in the southwest, and south Essex woodlands.
Exmoor is now considered the most important stronghold for the species and the early successional habitats it depends on — dominated by bracken, heather and gorse, with plentiful cow-wheat — require ongoing, sensitive management to sustain.