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Rare large heath caterpillars hatch at Chester Zoo

Large heath caterpillar by Chester Zoo

Two months after we collected pregnant large heath butterflies from a special donor site, more than 150 rare caterpillars have hatched in their temporary home at Chester Zoo, destined for release on peatlands where they have been extinct for over a century.

The Chester Zoo butterfly team is working in partnership with us to raise these caterpillars to help prevent their extinction.

Each member of the army of freshly hatched large heath caterpillars are currently only a couple of millimetres long. Conservationists at the zoo have been using fine art paintbrushes to move the miniscule species into their specially designed habitats at the zoo. These paintbrushes allow the zoo’s invertebrate keepers to be precise and delicate when handling the precious insects.

After plenty of eating and growth, these tiny youngsters will hibernate over the winter and pupate next year, emerging in the summer as large heath butterflies. These adults will be the first to return to areas that their species once called home: Astley Moss in Greater Manchester and Risley Moss in Warrington.

Close-up of the head of a tiny large heath butterfly caterpillar

Large heath caterpillar by Chester Zoo

Large heath butterflies were once common across north west England but over the last 200 years they have become extinct in much of their former range. Large colonies previously at home in the boggy Mosses around Manchester and Liverpool have long since been lost to local extinction.

As the UK has built up its agriculture over the last two centuries, the wet peatlands that the large heath needs to survive have been drained and converted into farmland. As the land dried, the foodplants for the butterfly were lost, resulting in a cascade of wildlife disappearance.

The butterflies can be identified by their orange wings, each bearing six black and white ‘eyespots’ on the underside. We hope to ensure they will one day be a common sight across our region once again. 

Ben Baker, Team Manager of the Chester Zoo butterfly team, said:

“Few people realise that the butterflies we might see in our gardens, forests and peatlands across the UK are heavily under threat, with many species disappearing from their last strongholds throughout England.

“The Chester Zoo butterfly team already care for endangered and rare invertebrates from across the world, as well as these local butterflies. We are working extremely hard to stop these species from disappearing.

“It is an amazing privilege to play a part in embarking these rare caterpillars on their journey, returning the species to their historic home.

“Although miniscule in size at the moment, we’ll watch them grow and grow in our care over the course of the year, wishing them farewell in the spring.”

A tiny large heath caterpillar resting on the bristles of a paintbrush

Image by Chester Zoo

Mike Longden, our Lancashire Peatland Initiative Project Officer, said:

“This is a very special project to be involved in; nature lovers can follow the story from local extinction to rearing, release and beyond, played out entirely within the North West region.

“We know the future of these newly hatched creatures depends hugely on the conditions of the wild places they will be set free. The Wildlife Trust for Lancashire, Manchester and North Merseyside has been carrying out important work on our peatlands across the region for many years.

“We will continue to care for the chosen sites over these last few crucial months, to ensure the butterflies will have everything they need to survive and breed once they are released into their new home next year. We are establishing rare plants that support an abundance of life on the peatlands, and will provide a vital food source for the large heath butterflies.

“We are very proud to play a part in the tale of comeback of these regional relics.”

The breeding programme and reintroduction forms a key part of the Lancashire Wildlife Trust led 'Manchester Mosses Species Reintroduction Project'. Funded by £265,000 from Veolia and £25,000 from the Casey Group, the work is seeing a return of many long-lost plants and insects to special areas of conservation in the Manchester, Cheshire and Lancashire region. 

It is a collaboration between the Wildlife Trust for Lancashire, Manchester and North Merseyside, Cheshire Wildlife Trust, Natural England, North West Rare Plant Initiative, Warrington Borough Council, Wigan Borough Council, Salford City Council, Manchester Metropolitan University, Liverpool John Moores University, Chester Zoo, RSPB and Butterfly Conservation.

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