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Eastern garter snakes basking on rocks before winter

October

Eastern garter snakes, among the state's most abundant and commonly seen snakes, spend sunny fall afternoons basking on rocks to warm up. As temperatures drop they head underground to shared winter dens called hibernacula, often in rock crevices.

Why this time of year

MassWildlife says snakes become less active as temperatures drop and go looking for hibernacula, and that on warmer days they may come out to sun themselves. Fall afternoons with sun on the rocks are when a garter snake is most likely to be caught warming up before it dens for the winter.

How to notice it

  1. Pick a sunny fall afternoon and scan rock piles, boulders, or rocky outcrops in an open, sunny spot.
  2. Look for a snake with three pale yellow or greenish stripes running the length of a dark body, the common pattern of Massachusetts's eastern garter snake.
  3. Check sunny rocks near damp ground; MassWildlife says garter snakes are most abundant in and around damp habitats.
  4. If you spot one, watch from a few feet away without touching it. It is harmless and will move off on its own once it has warmed up.

Try this with kids: Can you find the snake's three racing stripes while it suns itself on a warm rock?

hibernacula: underground dens, often in rock crevices, where snakes spend the winter, sometimes sharing the space with other snakes or even other species.

Sources

  • mass.govMassWildlife: natural snake hibernacula are 'deep bedrock rock crevices, talus and traprock ridges', often shared by several snakes or species. The page's south-facing slope, open canopy and frost-line lines are construction guidance for building an artificial hibernaculum and are NOT cited here as facts about wild dens. (mass.gov returns 403 to automated fetch; read in a browser 2026-09-22.)
  • mass.govMassWildlife news 11/01/2022: gartersnakes are common and nonvenomous; snakes become less active as temperatures drop and seek hibernacula (rocky debris, mammal burrows, holes, stumps, rocks, logs), which several species may share; 'On warmer days, snakes may exit the "den" to sun themselves.' Gives no month.
  • mass.govMassWildlife: the common gartersnake is statewide in Massachusetts, 'among the state's most abundant', active during the day, and most abundant in and around damp habitats. Says nothing about fall behavior.
  • massaudubon.orgStates that Massachusetts snakes are ectotherms that bask in the sun to keep warm, that in fall they seek shelter in rock crevices and mammal burrows, and that it is not uncommon for different snake species to den together in winter.

Checked against these sources on September 22, 2026.

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