PORT ST. LUCIE, Fla.  —  Nearly 20,000 bats will be delaying a widening project for Interstate 95 in the Port St. Lucie area for four months.

The Mexican free-tailed bats are found under the highway's twin bridges — just above a canal. Workers are trying to replace and widen the concrete bridge decks of I-95 in one area as part of a new interchange to be built.

But crews can't work during the bats' maternity season, which is April through August. That means drivers will be faced with lane closures.

John Greenwood, of Friends of Bats, is monitoring the colony for the city's bridge consultant, American Consulting Engineers. He said it's important to preserve the bats, especially since each one eats 2- to 3,000 flying insects every night.

Project officials are optimistic the four-month waiting period won't delay the overall progress of the 30 million-dollar interchange.

It's scheduled to be completed in November 2009.