A population of rare Small Pearl Bordered Fritillary butterflies has been confirmed on DPA owned land at High House Waste. Our Ecological Consultant, Albert Knott, spent a day on the land last week surveying for the presence of these butterflies, and was delighted to record substantial activity. As well as seeing fritillary butterflies, he also saw multiple Keeled Skimmer dragonflies emerging from the mire habitat. The confirmed presence of these species further underscores the vital importance of the mosaic of moorland habitat, including mires, at High House Waste.
Mires can be challenging habitats to live in, but for specialist plants and animals they are a perfect refuge. The peat soil is very acidic, with a pH below 7, and it remains waterlogged year round, as well as being low in nutrients such as nitrogen. Mire specialists include Sphagnum moss, Cotton grass, sundews and Devil’s-bit Scabious, which is the main food plant for caterpillars of the Marsh Fritillary butterfly. Keeled Skimmer dragonflies are common in various areas of the UK and they are drawn to heaths and commons with shallow pools, where they can be spotted flying between June and September. The mire habitat at High House Waste offers the perfect mix of water and vegetation for Keeled Skimmers to breed.
Small Pearl Bordered Fritillary butterflies have suffered a severe decline in population and are a Priority Species under the UK Post-2010 Biodiversity Framework. They emerge first in the South-West, during the month of May, with emergence as far as Scotland not happening until June. Preferred habitats include woodland clearings and moorland with a liking for damp, grassy areas with a plentiful supply of marsh violets. Dartmoor is a stronghold for this threatened species, and the early emergence here means that, in some cases, it is possible for a second batch of eggs to be laid.
As an adult, Small Pearl Bordered Fritillary butterflies consume nectar from spring flowers including bramble and thistle, flying low to the ground in a distinctive flutter and glide pattern. They can be identified by their striking orange colour, with black marks on the upperside of the wings and black and silver markings on the underside. They also has a distinctive row of seven ‘pearls’ on the outer edge of each wing. The caterpillars feed exclusively on violets (both marsh violets and also common dog violets) and require an ample food source growing near a thatch of bracken, which helps to keeps eggs and caterpillars warm as they develop.
Our refreshed land management plan for High House Waste acknowledges the importance of mires and seeks to improve the health of this habitat on site. We plan to further clear gorse from around the edges of the mires, opening them up and allowing light in so that marsh violets can flourish in these areas. Under the guidance of Albert Knott, we will carry out this work during the autumn and then survey the area again next spring, looking for evidence of Small Pearl Bordered Fritillary butterflies and their food plants.
We are always looking for more Conservation Volunteers to join our friendly team, and would warmly welcome new faces to help us clear bracken and gorse at High House Waste. Volunteering with us is a fantastic way to get outdoor exercise, socialise with like-minded people and make a huge difference for species such as fritillary butterflies. Find a full list of upcoming workdays on our website.
Images: Albert Knott