
Large Heath (Coenonympha tullia)
Scottish Survey
The Large Heath is a specialist of wet, boggy peatlands in northern Britain, Ireland and a few isolated sites in Wales and central England. It breeds on lowland raised bog, upland blanket bog and damp, acid moorlands where their caterpillar food plant, Hare's-tail cottongrass (Eriophorum vaginatum), is found. The adults fly from mid-June to mid-August, but when sitting, they are always found with their wings closed showing the arc of eyespots on their underwings, which are absent in the similar-looking Small Heath butterfly.

Historically peatlands have been overlooked as a habitat, resulting in the drainage of lowland raised bogs for agriculture, afforestation and commercial peat extraction. Such habitat loss has led to this species declining, especially in England and Wales. Scotland remains a relative stronghold for the species in the UK, but with many lowland raised bogs being in unfavourable condition in Scotland, we are keen to gather a better picture of how Large Heath is faring across this habitat.
We only receive a handful of records for Large Heath each year, in part, probably due to the difficult terrain of bog habitat. To help us increase our records we rolled this survey out for the first time in 2022 and made a promising start, so we hope to build on this by gaining more data this year.
We hope this dedicated survey will increase our records, adding to our knowledge of the species distribution, abundance and habitat condition of lowland raised bogs. In turn this will provide valuable information that will help us prioritise the location of our peatland restoration work with the Bog Squad.
Training videos, guidance document and survey form
This summer we are looking for willing volunteers to take on a local bog to survey for Large Heath. Surveys will need to take place on a sunny day during the butterfly's flight period of June to mid-August.
To assist would-be surveyors we have two online training videos which cover ecology, identification, distribution and survey methods.
A guidance document and the survey form can be downloaded if you scroll to the bottom of this page.
- Large Heath Ecology and ID video: https://youtu.be/zkuCF7HRJ6g
- Survey Methods video: https://youtu.be/DjxaiOyR2ZE (this video is from our 2022 season, but still covers the same survey method)
Survey locations map
The Google map below shows the Large Heath sites that we have identified as survey priorities for this year.
There are two types of site:
- Lowland bogs where we hope to confirm that Large Heath is still present and assess the habitat condition.
- Upland 1km squares where we wish to establish if Large Heath is still present. These are squares where we have received 2 or more records previously but none post-2015
If you zoom in and then click on the marker, information on that site will appear in a box. It is also possible to navigate to different parts of the country.
If you are willing to survey any of these sites please contact Polly Phillpot @email and we will provide further information on the site.
There are many other lowland raised bog and upland sites across Scotland that have Large Heath populations and information from surveys of these would also be gratefully received.
Thanks to NatureScot's Peatland ACTION Programme for providing funding for this survey to take place.

Links for more information
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