Scotland's first wildlife bridges, which will allow animals to cross busy roads safely, are being built over the new Aberdeen bypass.

Two purpose-built bridges will cross the Aberdeen Western Peripheral Route (AWPR) in order to protect badgers, red squirrels, deer and hare.

The bridges will join up wooded areas and connect the animals' colonies, with mammal-proof fencing put in place in order to guide them to the sites.

Aberdeen Roads Ltd. has begun work on the two crossings at Kingcausie and Kirkhill as part of the £475m project to take the AWPR between Balmedie to Tipperty.

Design documents state the concrete bridges will have topsoil and shrubbery placed on top of them in order to make the structures appear more natural.

Along with a series of underpasses, they will allow wildlife to avoid traffic and prevent their habitats from being bisected.

Kirkhill's bridge will also provide a track for Forestry Commission vehicles but otherwise they are not designed for human use.

There are only a few wildlife bridges elsewhere in the UK, including one over the A21 at Scotney Castle in Kent.

There are plans for another wildlife bridge over the A9 near Luncarty in Perthshire.

The Netherlands pioneered the concept, also known as "green bridges", with others being built around the world.

A Transport Scotland spokesperson said: "This is a good example of the AWPR contractor implementing just some of the measures which are outlined in the Environmental Statement of 2007, which will help to maintain biodiversity in the north east following construction.

"These wildlife bridges, along with 17 mammal underpasses, have specially designed planting and strategic seeding to encourage biodiversity."

He continued: "These are just some of the measures that are considered necessary to ensure wildlife continues to thrive in the area once the road has been built.

"These 'green' bridges were successfully pioneered in the Netherlands in 1988, where they are known as ecoducts.

"There are also now a small number of these structures on some major routes in England."