That prickly but endearing mammal, the hedgehog, is in serious decline. UK numbers fell from a population of around 30 million in the 1950s to only 1½ million in 1995, a decrease of 95%. Hedgehog numbers have continued to plummet, falling by over a third between 2003 and 2012. There may now be fewer than a million left.

There are a number of factors that might explain this dramatic decline. Habitat loss and habitat fragmentation are of particular concern. The larger fields, fewer hedgerows and loss of permanent grassland that accompany intensive agriculture reduce the suitable habitat. Pesticides reduce the numbers of prey available to hedgehogs, and weather also affects the availability of prey, especially unusually wet or dry summers. This is likely to be exacerbated by climate change, which is expected to increase the occurrence of extreme weather.

New buildings and new roads eliminate suitable habitats, while increasing traffic increases the number of road casualties – tens of thousands of hedgehogs are killed on our roads each year.

The decline has been greater in rural areas than in urban ones because gardens have, in the past, provided valuable habitats for hedgehogs. However, even in gardens, suitable habitats are declining where gardens are smaller and tidier, or where lawns and flower beds are converted to patios, decking or hard standing for cars. In addition, fences and walls prevent hedgehogs moving from one garden to the next. Hedgehogs and other wildlife rely on connections between suitable habitats – referred to as wildlife corridors – to move around their territory and find food and shelter.

Gardens can also contain hedgehog hazards such as steep-sided ponds, strimmers, slug pellets, netting that can entangle the animals, or bonfires that they may crawl into for shelter.

In hedgehog-friendly gardens, lawns, flower beds and compost heaps all provide nutritious prey such as earthworms, beetles, snails, slugs and caterpillars. Gardens can also provide water and shelter and, if sufficiently undisturbed and secluded, can provide suitable areas for breeding and hibernation. In return, the gardener benefits from the large number of slugs and other garden pests that the hedgehog devours.

You can help your neighbourhood hedgehogs by making sure your garden provides a rich habitat that is free of hedgehog hazards. Also ensure that the animals can gain access by replacing fences and walls with hedges, or making small holes at the base so that hedgehogs can move freely from one garden to the next. A gap of only 15 cm is sufficient.