Small Tortoiseshell Butterfly Welfare and Decline

The small tortoiseshell is one of Britain's most familiar butterflies but has undergone significant population declines in recent decades.

Key Facts

Small tortoiseshell populations have declined by over 70 percent in parts of the UK
Adults hibernate as adults in cool dark locations including outbuildings
Nettles are the sole larval food plant
A parasitic fly Sturmia bella from mainland Europe may be contributing to UK declines
Adults are strong fliers and can travel long distances to find food and shelter

Welfare Considerations

Butterfly welfare considerations include the quality of habitat for both adults and larvae, and protection from parasitic and predatory threats. Larval nettles are abundant but butterfly abundance is limited by adult nectar sources and suitable hibernation sites. The spread of Sturmia bella, which parasitises caterpillars, may be shifting population dynamics. Climate change affects emergence timing and overwintering survival. Maintaining rich nectar sources and undisturbed hibernation sites benefits small tortoiseshell populations.

What You Can Do

Plant nectar-rich flowers including buddleia, lavender, and marjoram in gardens
Leave patches of nettles in sunny corners for butterfly larvae
Avoid disturbing outbuildings and sheds where butterflies may be hibernating
Contribute butterfly sightings to the UK Butterfly Monitoring Scheme