Species in serious decline

Long, slender and a decent swimmer, the grass snake is harmless to humans, but not to frogs. Six a year can keep this leisurely, grey-green reptile fed. Photograph: George McCarthy/Corbis

Hedgehogs are small, spiny mammals that have not changed much over the past 15m years. Nocturnal, insect-eating and once part of a rural diet, the hedgehog has been written about in English since at least 1450. Photograph: Corbis

The marsh orchid family is also at risk. Early, southern, northern, and narrow-leaved marsh orchids are all pinky-purple and can be found in bogs or fens. Photograph: Niall Benvie/Corbis

The otter is a playful river mammal, doing better after the hunting ban and habitat monitoring. Famous and loved through classic books like Tarka the Otter, the Wind in the Willows and Ring of Bright Water, this adorable water-dog can bite, and hard. Photograph: Susannah Ireland/EPA

The archetypal sweet ball of fur, Britain's smallest rodent weighs less than a 2p coin. The mouse likes tall grasses and nibbles their seeds. Conservation tools have included Wimbledon tennis balls, which have been recycled for use as artificial nests. Photograph: Roger Tidman/Corbis

House sparrows are not terribly picky eaters: stomach dissections on the birds have found 838 different foods. The house sparrow has seen an estimated decline of 50% in the last 25 years, along with the once ubiquitous starling. Photograph: Francesc Muntada/Corbis