How wildlife shapes roads plans

A stag peers down the tunnel of an underpass

It is part of a multi-million pounds effort to improve one of Britain's most northerly mainland roads.

The construction of the new two-mile stretch on the A836 between Melvich and Strathy in Sutherland has been designed to make journeys quicker and safer.

However, its engineering was also influenced by the area's wildlife - particularly otters.

Several underpasses punctuate the section to allow the mammals to go under the carriageway.

Ledges were also constructed above the flood line on the road's bridges for otters.

Fencing along parts of the carriageway aim to direct the animals to the 600mm diameter underpasses.

Monitoring of how well they are used can be done by laying some sand and checking for tracks.

According to Highland Council engineers and Scottish Natural Heritage (SNH), nature is considered at almost every stage of a development project.

Mike Mackintosh, an engineer in the council's Brora office, worked on the latest upgrade of the A836 North Coast Road.

The official opening of the new stretch of A836 North Coast Road

He said: "Before the job started, during the design stage, an otter expert looked over it and for tracks and holts.

"Where a holt is found we have to go through a licence procedure."

Alec Macdonald, SNH area officer for North Sutherland, said the Highlands have a strong otter population.

He said: "In our patch when there is anything to do with water you have to think about otters. It is something you have to think about right from the start."

Mr Macdonald said local council engineers were "switched on" to the need to consider wildlife.

Badgers and deer also have an effect on road building in the Highlands.

The recently upgraded Achnasheen to Kinlochewe features large stag underpasses.