Construction on the £65m Bontnewydd road was due to start towards the end of this year.
The Welsh Government said it rejected suggestions of "huge delays" to the scheme.
Orders detailing the project were due to be published in the spring. They are now expected to be made public in August.
Arfon AM Sian Gwenllian has said she fears the construction work could be put back by up to a year.
"The orders were supposed to have been published at the beginning of this year, and they haven't been, and it's likely that this scheme will not proceed for at least another 12 months," she warned assembly members last week.
"I understand that the problem is a dispute as regards what to do about the bats."
The six-mile (10km) route will take the new road around the current bottlenecks between Bontnewydd and Caernarfon, linking with the Felinheli bypass.
The new road will cross two rivers, and requires seven bridges.
A Welsh Government spokesperson said on Tuesday: "In order to assure everyone that the most appropriate environmental mitigation measures are being implemented, some short additional surveys are having to be undertaken in the next few weeks."
Officials said they expected construction work to get under way in August or September in 2017.
Welsh Government documents had suggested the work should have started by the end of this year.
Peter Evans,  the protected species officer for Natural Resources Wales, said the route passes close to a special area of conservation.
"There are concerns because this is a migration route for animals like the otter and the lesser horseshoe bat, which are protected species," he said.
"We are working with the developers at present to get more information about how bats use the land along the route."
Work on a major bypass in Gwynedd is facing delays as talks continue over protecting wildlife.