The bats cross the main road to reach feeding sites
Bats are being given a special crossing across a new road to stop them flying into cars.
The bat bridge will help the creatures navigate a safe route across the A487 after hedges and trees they used to follow were removed.
The bypass in Groeslon near Caernarfon will close for 12 hours on Sunday so the aerial crossing can be installed.
A spokesman said the assembly government was committed to protection and enhancement of protected species.
The road will be closed from the Groeslon roundabout to the Llanwnda roundabout from 0600 to 1800 GMT on Sunday, 31 January.
The spokesman said the bat bridge was part of "mitigating measures" to help the bats because of the road's impact on the Glynllifon Special Area of Conservation which is home to a lesser horseshoe bat colony.
The crossing will feature a pole on either site of the road with a thin line of net run between them.
He added that the bats would instinctively follow the poles and the net, rather than dipping into the traffic and being killed.
A spokeswoman for the Gwynedd Bat Group said the crossing was a good idea as the lesser horse-shoe bats follow lines of vegetation to reach feeding sites.
"Bats such as this follow a very specific route," said Sarah Cartmel, secretary of the Gwynedd Bat Group.
"They usually follow hedge and tree lines, so even the removal of a hedge will disrupt their flight."
Ms Cartmel said the bats stayed in vegetation to avoid predators, so crossed roads at points when trees either side created a canopy.
"A crossing is good for the bats as they don't fly out in the open," she added.