Number of small tortoiseshell butterflies at lowest level ever

Three Butterflies on Purple Flowers
Figures published by the UK Butterfly Monitoring Scheme (UKBMS) show tortoiseshell butterfly numbers have fallen by 82 per cent since 1976 - iStockphoto

The small tortoiseshell butterfly population in England has fallen to its lowest level since records began.

Figures published today by the UK Butterfly Monitoring Scheme (UKBMS) show their number has fallen by 82 per cent since 1976. The figures also showed that small pearl-bordered fritillaries declined by 71 per cent in that period.

Last year saw a mixed picture for 58 butterflies, with some species’ numbers soaring while others saw steep declines.

Volunteers and environmental organisations recorded data on 3,316 sites in 2023 as part of the annual scheme that monitors changes in insect populations.

Small Tortoiseshells, which are common in gardens, had their worst year on record in England, second worst in Wales and joint fifth worst in Scotland in 2023, the figures show – although they saw their second best year in Northern Ireland.

Large amount of small tortoiseshell butterflies
Volunteers and environmental organisations recorded data on 3,316 sites in 2023 as part of the annual scheme that monitors changes in insect populations - Moment RF

Other species which saw counts decline last year included the Cryptic Wood white, Grizzled Skipper, Pearl-bordered Fritillary, Grayling and Scotch Argus.

The Green-veined White and Ringlet also had a poor year, with conservationists saying this could be due to the ongoing effects from a drought in 2022.

Meanwhile, warming temperatures mean Red Admirals, a migratory species that have begun to spend winters in Britain, saw their highest ever count last year and were common in all habitats including gardens.

These butterflies have now increased by 318 per cent at monitored sites since 1976, the data shows.

Small Pearl-bordered Fritillary
The figures also showed that small pearl-bordered fritillaries declined by 71 per cent since 1976 - Alamy

Conservationists say efforts to restore the Large Blue, which was reintroduced to the UK after becoming extinct in the 1970s, have been successful with numbers hitting a record high in 2023.

Other species that flourished last year include the Chequered Skipper, Brimstone, Brown Argus, Marbled White, Comma, Black Hairstreak and Holly Blue.

Dr Marc Botham, a butterfly ecologist at the UK Centre for Ecology & Hydrology, said butterflies are an “indicator species” to the wider health of the environment. He said this makes the UKBMS data “invaluable in assessing the health of our countryside and natural world in general”.

He added: “The mixed results this year emphasise the need for continued monitoring and conservation efforts to protect these important species and their habitats.”

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