A night out with tag-team hedgehog

By Richard Black Environment correspondent, BBC News website

If you met Anouschka Hof by chance one moon-bright summer night, you might assume she was a TV licence detector gone feral, as she strides around the villages of north Norfolk brandishing a two-metre-long metal antenna.

If you came across her by the churchyard, she might even conjure up images of a hi-tech ghost-hunter seeking errant spirits under the moonlit sky.

But the prey for this particular hunt are much more homely; Anouschka is looking for hedgehogs.

"I work during the night, I sleep during the day - I become a hedgehog," she tells me.

The ambition is to find out where they go and how they live, trying to comprehend the factors that may lie behind their recent decline, and whether the modifications we are making to the landscape could stimulate a recovery.

The antenna provides a fix on the location of hedgehogs carrying tags

The antenna is listening for signals sent out by tiny transmitters which the researchers have stuck on the animals' backs.

Each transmitter sends out a unique code; so not only can you follow where the hedgehog goes, you can record and plot its movements night after night and compare its wanderings with the rest of the local group.

"Now and then you can sit somewhere and know they will just cross the road there, but now and then they do unexpected things," she says.

Adults will travel further than the young - often sticking close to hedges which give them protection from predators.

"Males have a larger home range, so they walk a lot longer distances each night to look for females.

"The females don't bother, they just stay around and they know the males will get there."

On the scent

When I meet the Royal Holloway, University of London, researcher, she is on the trail of a male which likes to roam along the boundary between a garden and a field, a boundary featuring a tall and straggly hedge.

Hedgehogs are in decline at the moment and it's nice to do something to find out what the reason is

The antenna is one way of finding him - the other is by looking for a tiny light within the transmitter unit.

We spot something shining in the hedge - but it turns out to be the eyes of a large black cat.

Completely unfazed by our presence, it seems for a moment determined to join our quest before sidling off in search of something more appetising.

Eventually, we track the male hog to a garden where we can see it lying still next to the hedge, adopting the time-honoured defensive tactic of hunkering down and hoping nothing happens.

It is a tactic that has worked for most of the species' history; the only natural predator capable of getting through that ball of spines is the badger.

We leave him alone on his midnight quest for food or a female, and walk down to Anouschka's car to have a look at some tags.

Stuck on you: Each hedgehog receives a tiny transmitter, secured with glue

As we arrive, so does research assistant Reda Garmute, carrying an untagged hedgehog she has found along the edge of a neighbouring field.

Here, the full glamour of cutting-edge science reveals itself as Anouschka prepares to fit it with a fresh transmitter, using scissors and a tube of high-strength glue.

As the animal nestles quietly in her lap, she trims the spines on a patch of its back, leaving stumps on which the glue will find some purchase.

Fifteen minutes later, the tag is fixed, and we return her - by now we know it is a female - back to the same place in the same field.

One more hedgehog is now added to the group that Reda and Anouschka will follow through the length of the Norfolk summer.

Away from the rat race

What would motivate someone to spend the best three months of the British year leading this unusual existence, secluded and nocturnal?

For Dr Hof, it is a combination of the research itself, and the need for it.

"I think it's important, because hedgehogs are in decline at the moment and it's nice to do something to find out what the reason is behind this decline.

"But if it had been rats I would eagerly have done rats."

Hedgehogs probably need the attention rather more.

The Mammals on Road survey suggested numbers fell nationwide by 20% between 2001 and 2005. The more recent HogWatch project also turned up hints that the population is shrinking, especially in the east of England.

The increasing tidiness of urban gardens has been suggested as a cause. So has the growing volume of road traffic, use of chemicals on farmland, and the spread of towns and villages.

A bench by a churchyard wall makes an impromptu workstation

The UK population of badgers, the hedgehog's sworn enemy, is believed to have risen in the 1990s - although there are suggestions of a decline since then - and some point to that as a natural check.

"I've heard this as well," says Anouschka, "but I always say hedgehogs and badgers have always been around together, so why do we suddenly see this big decline?

"I don't say badgers are not a reason for it; I say they're not the only reason for it."

Along with other EU countries, the UK government has in recent years introduced "agri-environment" schemes which reward farmers for measures intended to improve conditions for birds, mammals and insects.

And this is the reason why someone is prepared to pay for Anouschka Hof and Reda Garmute and others to spend long lonely nights in the middle of nowhere waving their antennas at passing hedgehogs.

The animals should relish the hedges that are being planted back, and the clear strips being left around the edges of fields.

But do they? And will such measures be enough to restrain the fall in numbers, and to make sure local hedgehog groups remain able to travel into the territories of neighbouring groups, which is essential for the long-term health of the species nationwide?

"We still don't really know what's good for them," says Anouschka.

"We think a lot, but we don't really know."

The fieldwork has now finished. When the data is analysed, we should know a little bit more about the prospects for this most fascinating of mammals.

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