The federal roads office on Thursday announced the cost of the plan to move 100 toads from a clay pit in the way of a 500-million-franc upgrade of the Belchen tunnel, near Hägendorf.
The toads are living in an area, near the south end of the 3.2-kilometre tunnel, where excavated material is to be deposited as part of the construction work.
The midwife toad is a protected species in Switzerland because its population is considered threatened.
So, since the beginning of the month members of nature protection groups have been capturing the nocturnal amphibians and moving them to a new home.
On a good night, 10 frogs are caught, biologist Christoph Bühler told the SDA news agency.
New habitat has been specially created nearby, protected by a 1.5-metre high stone wall, the agency reported.
The midwife toad was named Switzerland’s “animal of the year” last year by the environmental group Pro Natura.
The toad, which can grow to be 5.5 centimetres long, is inactive during the day, when it burrows into the ground, or finds shelter under stones and in mouse holes.
At night it forages for prey, such as spiders, beetles, slugs, maggots and worms.
When threatened, the wart-covered midwife toad inflates itself, filling itself with air so as to appear as large as possible.
It is found in eight European countries, including France, where it is common, Germany and Spain.