I TRY to support measures to encourage and protect wildlife but I do like them to be based on reasonable evidence and not just emotion. 
Thus, when I read that a tunnel for bats is to be provided on the A350 diversion at Yarnbrook to protect them from traffic I thought it seemed odd, as bats have this super detector system that can pick up flying insects, and they seem very agile and manoeuvrable. It seems to go against common sense that they should be hit by vehicles. 
It also seemed to me that the £4m extra cost would mean around £1,500 extra on the cost of each house and yet we need low cost houses as a priority.
So, I sought information on bat tunnels and found a useful site, which shows evidence that bats will use tunnels to some degree. However, I also found a year-long study of mammals and birds killed by traffic on roads such as A350 and importantly the report does not even mention bats. 
So traffic on non-motorway roads can’t really be a significant problem for bats.
The Bat Conservation Trust advises that “the Bechstein’s bat is a rare tree-dwelling bat, mostly associated with old growth broadleaved woodland. A few individuals are found in underground sites during hibernation, but it is likely that most individuals roost in trees all year. It feeds on invertebrates including spiders and resting day-flying insects which are picked from branches and leaves.” 
In a Bats Survey section it states “The Bechstein’s bat is one of the rarest of our mammals and a UK Biodiversity Action Plan priority species. Until now it has been difficult to detect as it rarely leaves the canopy of its favoured broadleaf woodland habitat.” So, if they generally stay within their woodland habitat why would they want to cross A350?
The woods between Green Lane and A350 cover an area of around 60 hectares, which appears to be sufficient to sustain a Bechstein bat colony. 
Instead of worrying about Bechsteins crossing A350 perhaps greater efforts should be put into enlarging the area of woodland, particularly with oaks. This would put a real buffer between Trowbridge and West Ashton village and with a bigger habitat, allow more bats to prosper. A win-win situation!
DAVID FEATHER
Broadley Park
North Bradley
Trowbridge