New Jersey has a lot of tunnels, but you've probably never seen ones like these. They're not for cars, trains or buses. They are instead for wildlife all over the state.

The tunnels at the Assunpink Wildlife Management Area in Monmouth County are helping endangered species survive. They're too small for a human but perfect for a frog no larger than a silver dollar.

"That is an approach we take to try to make the landscape in New Jersey more permeable for wildlife," said Dave Golden, the assistant commissioner for the New Jersey Department of Environmental Protection Fish and Wildlife.

A series of tunnels now provides safe passage for some of the state's smallest critters. The tunnels are known as Connecting Habitats Across New Jersey.

"Think about a frog that is only an inch long in size. How long does it take for that frog to get across the road and how many cars are coming down that road during that time?" said Golden.

The tunnel at Assunpink Wildlife Preserve cost $60,000, according to Golden.

Barriers help guide the animals to the entrance as they mate, migrate and search for food on both sides of the road.

According to DEP research studies, these tunnels work. In the five years since the one in Assunpink was constructed, it has reduced animal vehicular deaths by nearly 100%.

"Our goal is to really expand this and give wildlife a way to move to the landscape unimpeded and safely be able to utilize all this great space that New Jersey has worked to preserve," Golden added.

New Jersey has more than 800,000 acres of preserved space. The DEP has partnered with the Department of Transportation to ensure new construction projects in environmental hotspots will contain more wildlife tunnels.