Porthmadog's bypass bat bridge

Bat bridge beyond railway bridge 

It’s big, cost £650K, and carries a hedgerow used by maybe 100 lesser horseshoe bats a night.

The £35m Porthmadog bypass cuts through the flightpaths of a maternity roost of lesser horseshoes. Last July as many as 350 horseshoes were counted including the newly born.

One of the routes is along a hedgerow that is now about 5 metres above the newly excavated road and this is where the bridge spans the gap. Either side of the bridge is a solid 6 foot wall to shield the light averse bats from the beams of traffic passing below. Elsewhere the bypass has been built on an embankment and in these places culverts have been constructed along the lines of hedgerows to help the bats pass beneath the road without injury. In a couple of places these culverts are a massive 4 metres in height and width.

I was giving a talk to a local group and mentioned the bat bridge. There was much shaking of the heads about the expense but after the talk one member of the audience came up to say how pleased she was about the bridge. Something like ... ‘so much money is wasted on other things it’s good to see such a worthwhile investment. Wildlife teaches us lots of useful things and we should look after it.’

Opinion is obviously going to be divided. What do you think?

I’m not an expert but I think it was necessary to avoid significant losses of a scarce species. The inexorable growth of the human species (from 3 billion in 1960 to 7 billion in 2011) and its appetite for faster roads is not sustainable. Maybe we should have done without the bypass?

If you want to see what lesser horseshoes look like this is a short film of a hibernation count, under licence with the Gwynedd Bat Group, in the Vale of Ffestiniog. These might be some of the users of the maternity roost near the bypass. 

In February 2011 there were 58 bats hibernating here which was just half the number of a year ago. This might have been due to the extreme cold weather combined with the exposed aspect of the adit resulting in the bats hibernating elsewhere. Hopefully we will see an increase in milder winters.