A prickly problem

IS the hedgehog's decline is a temporary blip, or a long term trend for this prickly creature that has outlived the mammoths and sabre toothed tigers? SIMONE BULLION, Suffolk Wildlife Trust's senior conservation officer, investigates.

HEDGEHOGS have been around for a very long time, about 20 million years in fact.

The ancestors of our modern hedgehogs have seen sabre-toothed tigers, mammoths, woolly rhinos, Irish elks and aurochs diminish to extinction, yet this ancient animal has persisted to the present day. Their skeleton and teeth have certain primitive features that imply that the 'mark one' hedgehog has altered very little through the millennia.

They are one of the very few British mammals able to hibernate during winter, thereby avoiding starvation when their invertebrate food source becomes scarce.

During the last decade, there has been a general feeling that hedgehogs may be declining, but without scientific evidence to back this up, it is very difficult to assess this.

In 2000, Suffolk Wildlife Trust carried out a countrywide survey of hedgehogs in gardens and received nearly 2,000 responses from Suffolk residents. Just over half of the people seeing hedgehogs stated that there was no change in the numbers of hedgehogs seen during the last five years, although many of the remainder felt they were less common than before.

However, the Mammals Trust UK launched a national Hedgehog Survey 2001 and the findings of this study reported that the numbers of hedgehogs found dead on the roads of East Anglia had fallen by 50 per cent compared to a similar survey completed in 1991. These findings were thought to be due to an overall decline in hedgehog numbers rather than an improved ability on the part of the hedgehogs to avoid being squashed. Similarly, results from the People's Trust for Endangered Species 'Mammals on Roads' survey show that between 2001 and 2004, there was a drop of 25pc for hedgehog counts across UK roads as a whole.

So it does appear that hedgehogs may be declining in numbers, but reasons for this are likely to be complex. Firstly, although they are relatively unspecialised, hedgehogs have had millions of years to adapt to their environment and become a successful resident of a range of habitats eating a variety of different foods. They also have an excellent way of deterring the unwelcome attentions of predators and avoiding food shortages in winter.

Unfortunately these factors are unlikely to be sufficient to equip the hedgehog with a strategy to cope with life in our modern world.

The last 50 years has been a period of immense change in both the countryside and our towns. The intensification of agriculture, which began in the 1950s, has led to a less diverse landscape and correspondingly, fewer hedgerows, woodlands and pastures where hedgehogs normally thrive.

Increased use of pesticides at the same time will have reduced the quantity and quality of their food, as well as possibly having direct impacts through contamination. Although there is no data available for hedgehogs, it has been shown in other animals that these poisons can accumulate in fat deposits, leading to problems with breeding success of even death.

Juvenile hedgehogs suffer from a very high mortality rate and at least two thirds are likely to die within the first year of leaving the nest. Being able to find enough food is a critical factor and in cold or very dry summers this can lead to starvation. Similarly, if a young animal is unable to accumulate enough fat reserves to get it through the winter it is unlikely to hibernate successfully. Indeed, it is in late autumn when small hedgehogs can be seen during daytime, in a desperate attempt to find enough food to fatten up before the cold weather strikes.

The expansion of urban areas into the countryside is probably less of a threat as far as hedgehogs are concerned, because the mosaics of gardens would fulfil their habitat requirements. However, the current trend in building high-density housing estates is likely to have an impact, because the gardens themselves are so small and consequently are less likely to have 'wild' corners. 'Back-land' development, where several large gardens are severed to accommodate more houses is also likely to have a similar effect.

Recently there has been an increase in the number of roads and phenomenal rise in the numbers of vehicles using them. Hedgehogs are unusual because their normal response when disturbed or threatened is not to run, but to roll up and sit tight until the danger goes away. This strategy is clearly no defence in the face of an approaching vehicle and the effects are likely to be worst where suitable habitat is adjacent to roads that are busy at night-time. Road casualty hedgehogs provide valuable data for surveys, and a decrease in casualties is thought to reflect a decline in hedgehogs.

Most recently, the People's Trust for Endangered Species 'Living with Mammals' survey has shown that there has been a dramatic decline in the average number of hedgehogs seen in the East of England in 2005, as compared with 2004. This decline is mirrored in the North West.

Only through long term monitoring will it be possible to assess whether this reflects a real decline, or simply the difference between a good and bad year for hedgehogs.

So what can be done to ensure that the hedgehog doesn't join the list of other threatened mammals? On a large scale, the Government's new agri-environment schemes will bring incentives to ensure that features like hedgerows, buffer strips and field corners improve habitat diversity. This will help improve diversity and abundance of invertaebrates, as well as opportunities for shelter benefiting a wide range of animals, not just hedgehogs.

Development of local land, however dense, needs to be designed to ensure that wildlife can still move within it and that these corridors connect to an overall wider 'ecological network'. This may mean leaving an undeveloped strip on the margins or within the area to be affected, which itself connects to the wider countryside, a river or railway line corridor. We have been working with planning authorities and developers throughout Suffolk to successfully ensure that this type of green infrastructure is incorporated into a number of large developments.

Finally, where roads are being upgraded, such as the modification of the Haughley Bends, we highlight the need for faunal underpasses at an early stage to ensure the safe passage of a wide range of animals. These usually take the form of large culverts in conjunction with fencing to encourage animals to follow this route under the road.

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A version of this article first appeared in Suffolk Wildlife Trust's magazine for members called Wildlife. Join online at www.suffolkwildlife.co.uk/join.

Hedgehog's spines are actually modified hairs. These spines help protect them from predators, and because they are good climbers, they have a cushioning effect should the intrepid hedgehog fall.

Using special muscles to roll up into a tight ball is also a characteristic feature of the hedgehog and each spine has its own tiny muscle that causes them all to point in different directions, thereby creating a bristling defence.

ONE of the hedgehog's main predators, the badger, increased by over 70% between 1985 and 1995 and this trend is continuing.

This is almost certainly due to a reduction in persecution, although like hedgehogs, considerable numbers of badgers are known to be killed on roads.

However, national studies have shown that where badger sett density is high, hedgehog numbers are very low and this inverse relationship was also apparent in our survey of 2000. Badgers stand less chance of killing a mature hedgehog, but it is the young hedgehogs that are particularly vulnerable as their muscles used for rolling up are not as well developed and their spines are less rigid. This means that if they roll up when threatened, there is a small gap close to their belly that is undefended. It is possible to find the discarded, empty, spiny skin of a hedgehog that has been predated in such a way.

l Leave rough areas in your garden, where the grass is allowed to remain longer and perhaps where a small amount of bramble can grow, to provide opportunities for hibernation as well as summer foraging areas.

l Rake fallen leaves into piles, and keep in a corner where a hedgehog might be able to use them to build a hibernation nest - even better if there is already a log pile in your garden.

l If you are burning debris or raking out compost heaps then always check these beforehand.

l Take great care when using a strimmer later this summer and check overgrown areas before cutting them.

l Use non-toxic methods to control unwanted pests and remember that hedgehogs do a good job in the garden because they eat lots of slugs.

l If you have a pond make sure that a hedgehog could climb out if it falls in - they can swim well, but they will drown if they are unable to scramble out.

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Put out small amounts of cat or dog food in dry weather, and to fatten hem up for next winter.