Large Heath Project

The large heath is an internationally endangered butterfly which has suffered a 50% UK decline in the last 30 years. It is identified as a priority species in the UK Biodiversity Action Plan. In Lancashire, prior to 2014 the large heath was only found at one site - Winmarleigh Moss SSSI.

Since 2012, we've worked with Lancashire Wildlife Trust (LWT) to restore the species to Heysham Moss, where it hadn’t been seen for over 100 years. 

After acquisition of the site in 2004, LWT undertook restoration work at Heysham to ensure the habitat was suitable for the species. A rearing programme was initiated in 2013 with gravid female butterflies collected from Winnmarleigh Moss.

Heath butterfly

We also constructed bespoke enclosures at the zoo to receive the butterflies for egg laying and rearing larvae to pupation. In 2014 and 2015 pupae have been transported to Heysham Moss, and adult butterflies released once emerged. A third and final rearing cycle is in progress.


  • Habitat restoration of lowland raised bog at Heysham Moss
  • 230 adult butterflies released at Heysham over two years
  • Mating butterflies observed at the release site after each release
  • Large heath life cycle completed in the wild at Heysham between 2014 and 2015
  • Awareness raised about fragile lowland bogs and their species

Ongoing monitoring is in place for 2017-2020 to assess the sustainability of the reintroduced population of large heath butterflies at Heysham Moss.

Project partners

The Wildlife Trust, Lancashire logo LEF

Project team

Key Facts

The butterfly has declined seriously in England & Wales, but still widespread in parts of Ireland & Scotland
The caterpillars eat Hare's-tail cottongrass (Eriophorum vaginatum)
Adult large heath butterflies are only around for a short period - between June & August, with a peak in mid-July

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