The Tale of the Large Tortoiseshell

Photo One by By Hectonichus - Own work, CC BY-SA 4.0,

Large Tortoiseshell (Nymphalis polychloros) (Photo One)

Photo Two by By Jörg Hempel, CC BY-SA 3.0 de,

Small Tortoiseshell (Photo Two)

Dear Readers, in the 1940s you would have seen large and small tortoiseshell butterflies on the scrubby edges of forests, but in 1980 the large tortoiseshell was declared extinct in the UK. The possible reasons were many. One was that the caterpillars of the large tortoiseshell feed on elm (unlike those of the small tortoiseshell, which feed on nettles0, and as we know, elm populations crashed following the introduction of Dutch elm disease. This on its own has reduced many species to a remnant of what they once were, but for the large tortoiseshell there was also the habitat of the adults to consider – they feed on the nectar of willows in the spring, and in the UK ‘scrub’ seems to have become a dirty word. Many scrubby areas have been rooted out and either planted with crops or with pine plantations. Large tortoiseshells seem to be particularly prone to parasites that destroy their caterpillars and eggs, and, as the caterpillars feed on the very top branches of trees, they are susceptible to predation by birds.

However, this year comes the news of yet another success at Knepp, famous for its rewilding project. Knepp has seen a burgeoning population of turtle doves, nightingales and many other creatures, and this year, large tortoiseshells have bred. This isn’t the first time that the butterflies have reproduced since their official ‘extinction’ – the butterfly migrates from mainland Europe, and there may have been some rump populations that have staggered on since the 1950s. The butterfly has been seen regularly on the south coast Some butterflies are bred and then released by mavericks trying to reintroduce species, which can make monitoring the actual status of a species very difficult. However, Knepp has a particular policy of restoring habitat rather than introducing species, and the conservationists worked very hard to restore the willow scrubland that the butterflies enjoy. The lepidopterists involved in the project  believe that while there might be some captive-bred butterflies about, too many are spotted crossing the Channel now for it to be all about releases – some butterflies are clearly making the crossing themselves and will breed if the habitat is suitable.

Photo Three by By Abrahami - Own work, CC BY-SA 3.0,

Large tortoiseshell caterpillar (Photo Three)

So, it just goes to show that if the habitat is correct, and if a species still exists in mainland Europe, it is possible to encourage them to return naturally. I look forward to hearing further tales of how the rewilding at Knepp is doing, and what other animals might turn up. It’s good to have a positive story for once, when so much is being lost.

You can read the whole story here.

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