Every spring, a stretch of road is closed on rainy nights in Princeton — not for repairs, but to protect hundreds of salamanders heading to their annual breeding grounds. Princeton police sent out an alert to residents stating that Herrontown Road between Snowden Lane and Poor Farm Road would be closed between 8 p.m. and 6 a.m. to allow salamanders — and sometimes frogs — to cross safely. "These 'keystone species' play a vital role in our local ecosystems, and this short migration period is critical for their survival," Princeton police said. "Please use detours via Terhune Road or Blue Spring Road and avoid walking on the closed roadway." The road is expected to close multiple times throughout spring to allow the tiny creatures to cross. The migration usually happens on warm, rainy nights and can begin anytime in late winter or early spring. According to the New Jersey Department of Environmental Protection, when it’s not breeding season, some salamanders occupy underground tunnels and burrows or find shelter beneath logs and piles of leaves. Princeton police are asking drivers in the area to slow down, use caution and follow all road closure and detour signs.