WARM British winters are not just sending plants haywire. Hedgehogs have emerged as the latest casualties of rising temperatures because the winter is not cold enough for them to hibernate but not warm enough for there to be sufficient food.

Animal rescue workers have reported a surge in the number of the creatures brought in by members of the public who have found them in a disoriented and weakened state.

The hedgehogs are not the only animals whose behaviour is being disrupted by rising temperatures. Butterflies and bumblebees that do not usually emerge until the spring were spotted as early as December.

“This change in temperature is a big problem,” said Nick Collin-son, head of conservation policy at the Woodland Trust. “Our winters are becoming more topsy-turvy with a particular feature now being very mild long-lasting periods with cold snaps.”

Sudden drops in temperatures during very mild winters put some animals at particular risk of dying. At St Tiggywinkles, a wild-life hospital near Aylesbury, Buckinghamshire, 550 hedgehogs have been handed in since September, compared with 300 over the same period last winter.

Lisa Frost, research manager at the hospital, said that by December the hedgehogs’ usual diet of snails and insects had diminished. “They are simply not hibernating and are coming out in daytime because they are so hungry and are being spotted by the public in an ill and weak condition,” she said.

Hedgehogs normally hibernate between late December and the middle of April. Because large numbers are no longer doing so, many are being caught out by cold snaps or lack of food.

Signs of distressed hedgehogs include finding them away from nests in the daytime, shedding spines or dragging their legs.

At the hospital, the hedgehogs are fed up to six times a day with cat food. Many are dehydrated and some weigh as little as 7½oz; the usual weight is nearer 1lb 6oz. Frost estimates the hospital will release 600 into the wild this spring, three times as many as usual.

The annual Springwatch survey by the Woodland Trust and the BBC is a stark indicator of the impact of the warmer weather.

Frogspawn was first seen in south Wales on December 1, several weeks earlier than the 30-year average.

There were sightings in the southeast of bumblebees in mid-December. The peacock butterfly, not normally spotted until early April, has already been widely recorded, with the first sighting on December 23.

As early as last October, there were reports of a “phantom spring” with flowers pushing through the soil because of high temperatures. Last week strawberries were picked on a farm in Kent. Its growers claimed the crop, a variety developed to exploit changing weather, was the earliest ever harvested in Britain.

As the real spring is now nearing, gardeners are being advised to carry out some jobs earlier than usual. The Royal Horticultural Society (RHS) is recommending for the first time this year that gardeners prune roses and clematis in January rather than the traditional month of March.

With an average temperature of 9.5C for the six months from September to February, up from 7.8C on the previous corresponding period, increasing numbers of householders are now mowing lawns year-round to prevent grass becoming unmanageable by the spring.

Guy Barter, head of horticultural advisory services at the RHS, said it had updated its website with the new advice and gardening books would also have to be revised. “We have had so many mild winters now that some garden authors are realising they need to respond and change their advice,” he said.

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