London Zoo is spearheading the biggest ever study of the health of the nation’s wildlife in a bid to halt the decline of iconic garden species such as the hedgehog.

Garden owners in Camden and Haringey are being encouraged to report sightings of wildlife as part of the landmark Garden Wildlife Health project, which has received the backing of the British Trust for Ornithology (BTO), Froglife and the Royal Society for the Protection of Birds (RSPB).

Organisers hope that data from the public will help reveal the reasons for a mysterious decline in the numbers of hedgehogs, common frogs and other species which, they say, could be falling victim to an unknown disease.

The London Zoological Society, the conservation charity that runs London Zoo in Regent’s Park, is calling on garden owners to monitor amphibians, reptiles, garden birds and hedgehogs and report signs of ill health.

Tim Hopkins, co-ordinator of the Garden Wildlife Health project, said the campaign aimed to finally explain the reasons behind the decline of some species.

He said: “A number of surveys have identified that there has been a dramatic decline in the populations of hedgehogs in both urban and rural environments.

“We know very little about how disease is playing a role in the decline.

“We know that disease played a role in the decline of the green finch population between 2006 and 2010, when we lost nearly a third of that population due to a parasitic disease.

“We want to find out whether something similar or related might be contributing to the decline of hedgehogs and other species.

“Keeping an eye on our British garden species is crucial if we are to understand the threats to their health, which not only affect individual animals but can impact on entire populations.”

Simon Olley, of the Friends of the Parkland Walk conservation group in Haringey, said that sightings of iconic British animals in the area “seemed to be in decline”.

He said: “On the last inspection of the Parkland Walk we were amazed at the level of species decline.” Mr Olley said there had been no sightings of hedgehogs – once a common sight in the area’s parks – in three years.

He added that slow-worms had not been spotted for a decade and that the last report of a muntjac, a small breed of deer, had been 15 years ago.

The Garden Wildlife Health project has received funding from the Department for Environment, Food and Rural Affairs, and the project hopes to engage a core team of 6,000 people who will report activity in their gardens, as well as a number of volunteers.

Kathy Wormald of Froglife added that the public could provide “invaluable information” in the struggle to prevent amphibians succumbing to infectious disease.

* Residents can find out how to participate in the project by visiting its website at www.gardenwildlifehealth.org