The hedgehog has long been a frontrunner for Britain’s most beloved wild mammal. It topped a recent poll by BBC Wildlife Magazine to choose the best symbol for British wildlife. That’s probably because it’s a great way to introduce small children to nature and wildlife, be it the real thing or Beatrix Potter’s Miss Tiggywinkle.

It’s small, harmless and too slow to flee in a flash when discovered. Instead, it sweetly rolls up in a ball when threatened. The hedgehog is also a favourite of gardeners because it eats pests like slugs and snails. We gave it quite a bit of space in The Nature of Gardens, the report we published with B&Q on wildlife and gardens last week.

But all of this affection has not spared the hedgehog from a significant population decline in the UK and other western European nations in recent decades. The exact cause is not known and there are probably several factors.

These include road kills (rolling up in a ball is not a good plan on the highway) and fragmentation and loss of its preferred semi-natural habitats of hedgerows and woodland edges (it gets its name from its love of its hedges and its piggy little snout).

As well as removing or neglecting hedgerows, modern intensive farming has reduced the invertebrate creatures (molluscs, earthworms, insects) that hedgehogs depend on.

Badgers may also have played a role, too, although this is strongly contested by some conservationists. Badgers eat the same food as hedgehogs and they also eat hedgehogs; their numbers have been rising. Yet the two species have coexisted for thousands of years in the UK.

The depth and speed of the hedgehog’s decline is also a bit of mystery, given that they are difficult to count. Two different surveys of rural hedgehog numbers indicate declines of more than 9% a year between 2000 and 2014, continuing a population slump that began in the last century. That is a truly alarming plunge.

However, two established experts recently analysed hedgehog sighting data old and new and concluded that hedgehogs were still widespread in England, with the area in which they are found shrinking by only 5 – 7.4% over the past 50 years.

While hedgehogs are declining in the countryside, surveys show that their numbers within towns and cities are falling more slowly or holding level in the UK. Several UK and European studies found that hedgehogs live at much higher population densities in urban areas than in the countryside.

Why? Probably because people supplement their natural food supplies with petfood in gardens. They can also escape badger predation in towns and cities. And milder urban winter temperatures (the urban heat island effect) and better, more abundant hibernation sites in gardens increase their survival through the coldest months compared to their country cousins.

Yet the urban hedgehog faces one big hurdle – the garden fence. One hedgehog has to roam across many gardens in order to find food and a mate. It may be small and slow but it can travel one mile in a night and wander across over 50 hectares (half of a square kilometre) in a summer.

It has been estimated that a population of a few dozen hedgehogs needs a minimum of nearly one square kilometre of habitat to remain viable. Which is why one of the main aims of the campaign Hedgehog Street is to persuade people to create 13 cm-wide openings – Hedgehog Highways- at the bottom of their garden fences.

It’s one of our ten top starter tips for people who want to attract wildlife to their gardens in our report with B&Q, The Nature of Gardens.

The campaign is run by the People’s Trust for Endangered Species and the British Hedgehog Preservation Society. The BHPS also runs Hedgehog Awareness Week.

I can’t think of a better animal to focus some serious citizen science on, with ordinary people asked to survey and report on their hedgehog encounters. This is a much loved, well-known yet quite mysterious creature which we still have some chance of finding in our gardens.

Hundreds of thousands of citizens could help scientists understand what is happening to hedgehogs and how we can better conserve them; information which could then be fed back to us. If it could work for them it can work for other wildlife species too, and at the very least it would raise plenty of awareness. So let’s plan for some serious yet popular backgarden hedgehog science.