A Large Tortoiseshell settles briefely in woodland near Bolney in April 2022
Photo: Bob Foreman
Nymphalis polychloros, also known as the Large Tortoiseshell butterfly, is a native species of butterfly in the UK that has undergone a significant decline since the 1950s. The species is now considered to be extinct in the UK, although there have been occasional sightings of individuals that are believed to have been migrants from continental Europe.
The ecology of Nymphalis polychloros is closely linked to its habitat requirements, and the species is known to prefer woodland areas with a mix of deciduous and coniferous trees. The larvae of Nymphalis polychloros feed exclusively on the leaves of elm trees, which were once common in the UK but have been drastically reduced in numbers due to Dutch Elm disease.
Adult butterflies feed on nectar from a variety of flowers, including bramble, thistle, and knapweed. The species is known to be relatively long-lived, with some individuals surviving for up to a year, and the adult butterflies are active from early spring to late summer.
The decline of Nymphalis polychloros in the UK has been linked to a combination of factors, including loss of habitat due to changes in land use, the loss of elm trees due to Dutch elm disease, and changes in climate. The species is also vulnerable to agricultural pesticides and other pollutants, which can have a negative impact on butterfly populations.
Efforts are currently underway to reintroduce Nymphalis polychloros to the UK through the captive breeding and release of individuals into suitable habitats. However, the success of these efforts will depend on the availability of suitable habitat and the ability of the released individuals to establish breeding populations.
There is however, evidence of natural recolonisation in Sussex and individuals have been observed in recent years in various scattered, mainly woodland, sites across the two counties. Although they have been observed throughout the summer months, late March and April is one of the best times to see this species as it is when adults that have overwintered here are waking from hibernation.
In conclusion, the ecology of Nymphalis polychloros in the UK is closely linked to its habitat requirements, making it vulnerable to changes in land use and the loss of elm trees due to Dutch elm disease. The decline of the species in the UK highlights the importance of wildlife conservation efforts to protect and restore habitat, and to safeguard vulnerable species from the impacts of climate change and other human activities.
If you are lucky enough to spot this rare butterfly, please enter the details of your observation (ideally with a photo) on iRecord.
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Every month it is our aim to highlight a species that is “in-season” and, although not necessarily rare or difficult to identify, has been highlighted by our local recording groups as being somewhat under-recorded and for which new records would therefore be welcomed.
If you or your recording group are aware of species such as this then please contact Bob Foreman.