Large Tortoiseshell Butterfly Declared a Resident Species in UK After Decades-Long Absence
London, 11 March 2026 – In a landmark announcement for British conservation, the large tortoiseshell butterfly (Nymphalis polychloros) has been officially declared a resident species once more, ending its status as extinct in the UK. This follows a remarkable flurry of sightings across southern England in recent weeks, prompting Butterfly Conservation to confirm the colourful insect’s return. The charity now classifies the butterfly as a resident breeding species for the first time in over half a century.
The Remarkable Return
Once a fairly common sight across England and Wales, the large tortoiseshell underwent a dramatic and rapid decline in the 1950s, vanishing from the British landscape. It was widely accepted that the species had become extinct in the UK, a fate largely attributed to the devastating impact of Dutch Elm disease on its larval host plants. For decades, it survived only as an occasional, scarce migrant from continental Europe. However, persistent sightings over recent years, culminating in a significant surge this early spring, have provided the evidence needed for conservationists to formally recognise its re-establishment.
The first reported sighting of 2026 was on the Isle of Wight on 24 February. Since then, members of the public and enthusiasts have reported over 20 further sightings along the south coast, including in Kent, Sussex, Hampshire, Dorset, and Cornwall. This consistent pattern of observations, coupled with confirmed breeding evidence dating back to 2020, indicates the butterfly is now successfully breeding and overwintering in the UK, moving it from the “extinct” category to a bona fide resident.
Key Facts: The Large Tortoiseshell
The following table details the essential characteristics and recent status change of this rediscovered butterfly.
| Category | Details |
|---|---|
| Scientific Name | Nymphalis polychloros |
| Family | Nymphalids (Brush-footed butterflies) |
| Wingspan | 68-75mm (Medium to Large) |
| Historic UK Status | Common resident, then declared extinct in the latter half of the 20th century. |
| New UK Status (2026) | Confirmed resident breeding species. |
| Primary Habitat | Woodland, particularly areas containing sallow trees, which provide a key nectar source. |
| Primary Cause of Decline | Dutch Elm disease devastating its larval foodplants. |
| Recent Sightings | Kent, Sussex, Hampshire, Isle of Wight, Dorset, Cornwall (February-March 2026). |
Conservation Significance
The return of the large tortoiseshell is being hailed as a significant “conservation optimism” story and a rare example of a de-extinction process occurring naturally. Its re-establishment raises the total number of resident butterfly species in Britain. While the exact reasons for its comeback are not yet fully understood, experts suggest a combination of factors including climate change, possible adaptations to new host plants, and naturally colonising migrants from Europe may be at play. The announcement serves as a powerful reminder of the resilience of nature and the importance of ongoing monitoring and habitat conservation.
Frequently Asked Questions
Is the large tortoiseshell butterfly still extinct?
No. As of 9 March 2026, following a review of mounting evidence, Butterfly Conservation has officially declared the large tortoiseshell a resident species in the UK, removing it from its extinct list.
Where can I see the large tortoiseshell in the UK?
The most recent flurry of sightings has been concentrated along the south coast of England, particularly in counties like Kent, Sussex, Hampshire, Dorset, and on the Isle of Wight. It favours woodland habitats, especially in early spring when it seeks out sallow blossom.
Why did it go extinct in the first place?
The primary cause of its extinction in Britain is widely linked to the outbreak of Dutch Elm disease, which killed vast numbers of elm trees. Elm leaves were a principal food source for the caterpillars, leading to a catastrophic collapse in the butterfly’s population.
What does this mean for UK biodiversity?
The return of a species once considered lost is a major positive event for UK biodiversity. It increases species richness and offers hope for the potential natural recovery of other insects, provided suitable habitats are maintained and enhanced.