Every year, warming spring days trigger amphibians like spotted salamanders and wood frogs to migrate en masse to vernal pools to breed on the night of the first soaking rain above 45°F—a phenomenon known as “Big Night.” This spectacular annual event is taking place all across Massachusetts.

Vernal pools are temporary, isolated ponds that form when spring rain and meltwater from ice and snow flood into woodland hollows and low meadows. These pools provide critical breeding habitat for certain amphibian and invertebrate species—since vernal pools eventually dry up, they are inaccessible and inhospitable to predatory fish.

To celebrate the return of spring and the mass migration now taking place all around us, here are five great photos of native salamanders. Note that not all salamanders migrate to and breed in vernal pools—the eastern red-backed salamander, for example, has no aquatic larval stage at all, so you’re most likely to find one under a moist, rotting log or rock while northern dusky salamanders are stream denizens and lay their eggs in flowing seeps in June or July.