Scientists warn of overlooked decline in moth population

Some of Britain's most beautiful moths, larger and more spectacularly coloured than many butterflies, are tumbling in numbers, sparking fears that the nation's moth population is in serious decline.

Some of Britain's most beautiful moths, larger and more spectacularly coloured than many butterflies, are tumbling in numbers, sparking fears that the nation's moth population is in serious decline.

If confirmed, this will have direct consequences for much of Britain's wildlife. Moth caterpillars provide essential food for many types of common birds, from blue tits to cuckoos, and fully grown moths are a staple in the diet of other birds, insects, lizards and small mammals, especially bats.

Figures released by the charity Butterfly Conservation reveal that when records dating back 30 years for six relatively familiar and widespread moth species were examined, five of them showed severe declines, both in distribution and in numbers.

The population of the dramatically coloured garden tiger moth, a mixture of cream, brown, scarlet and black, has dropped by 44 per cent across Britain. Its large hairy caterpillars, known as "woolly bears", were familiar to generations of children.

Declines among other species are even greater. The white ermine, which looks as if it is wearing a robe for the House of Lords, has gone down by 75 per cent; the lackey, a buff-coloured, fast-flying moth, by 72 per cent; the figure of eight, so-called because of a distinctive wing marking, by 64 per cent; and the magpie moth, a handsome black, white and yellow insect whose caterpillars are known to anyone with gooseberry bushes, by 42 per cent. Only one of the six species examined - the ruby tiger - has increased in numbers (by 32 per cent).

Unlike population declines in British birds, wild flowers and other insects such as butterflies, which are very well documented, these startling falls have been overlooked, because they are not visible to the casual observer (especially as most moths fly only at night). But they have been picked up by examination of data held by Rothamsted Research, Brit-ain's oldest agricultural research station, at Harpenden in Hertfordshire. Rothamsted's insect survey dates back more than 30 years.

It works with an extensive national network of traps, where moths are attracted to a bright light and fall into a trap beneath. Rothamsted scientists looked at the data for the garden tiger moth, which they feared was in decline. They confirmed this suspicion and then looked at the five other species, which have similar characteristics.

Ian Woiwod, the scientist in charge of the research, said: "We were very surprised. And it's not just a question of some species going up and some going down. There is an overall decline in the numbers of moths being caught."

He said that climate change, and the consequently wetter, warmer winters Britain was experiencing, might be implicated in the decline of the garden tiger moth. The insect overwinters as a caterpillar and it may be subject to fungal attack in damp conditions. In warm winter weather, it may emerge from hibernation "out of sync" with its food plants.

Butterfly Conservation, the charity dedicated to saving butterflies and moths, has secured a £120,000 research grant from the Esmée Fairbairn Foundation to enable the Rothamsted records of 350 moth species to be examined in detail over the next two years, to see just how widespread and steep the falls in numbers are. Martin Warren, chief executive of Butterfly Conservation, said: "The preliminary findings are shocking.

"They suggest that many common moths may be suffering considerable declines. Moths and their caterpillars are a vital part of the food chain, and our results will help us understand how serious the knock-on effects of their declines will be for other species."

One such species is already in the frame: the cuckoo, which alone of Britain's birds eats tiger moth caterpillars, which are poisonous to other species. Cuckoo numbers are known to be declining in southern Britain and the disappearance of the garden tiger moth may be a factor in that trend.

Switch your Gas & Electricity and save up to £380 with Independent Compare