Northern New England's annual amphibian migration is always perilous, and critters that cross roads to breed are facing an additional challenge this year: a delayed start due to the long winter.

Salamanders and frogs travel to vernal pools — temporary bodies of water created by melted snow — to mate and lay eggs each spring, and the resulting offspring need several months to develop and grow legs before the pools dry up in summer. Wildlife officials say the migration is running a week or two behind this year in Vermont, Maine and New Hampshire, cutting into that critical development time.

Officials are urging people to stay off the roads on rainy spring nights or to slow down to avoid hitting them as they cross the street.