Significant Wildlife Habitat:
Significant Vernal Pool Habitat

Related page: Natural Resources Protection Act (NRPA) Page, including licensing materials and contacts.


Vernal pools or "spring pools" are shallow depressions that usually contain water for only part of the year. "Significant vernal pools" are a subset of vernal pools with particularly valuable habitat. Starting September 1, 2007, significant vernal pool habitat is protected by law under the Natural Resources Protection Act (NRPA).


Determining the significance of a vernal pool

  • The DEP may provide a written determination concerning whether or not a vernal pool habitat is significant. Call your nearest DEP regional office and ask to speak to the on-call person in "Land & Water" in order to request a field determination.
    Presque Isle (Northern Maine Regional Office):  207-764-0477; 888-769-1053
    Bangor (Eastern Maine Regional Office):  207-941-4570; 888-769-1137
    Augusta (Central Maine Regional Office):  207-287-3901; 800-452-1942
    Portland (Southern Maine Regional Office):  207-822-6300; 888-769-1036
  • In any season, indicators of a vernal pool may include flat topography with depressions or pit-and-mound topography, fingernail clams, caddisfly cases, and evidence of temporary flooding.
  • Vernal pool significance must be determined and documented by an individual who has experience and training in either wetland ecology or wildlife ecology and therefore has qualifications sufficient to identify and document a significant vernal pool. For more information on identification, see Chapter 335, and this fact sheet: Vernal Pools - A Significant Wildlife Habitat.
  • Abundance. Any one of or combination of the following species abundance levels, documented in any given year, determine the significance of a vernal pool.
    Species Abundance Criteria
    Fairy shrimp Presence in any life stage
    Blue spotted salamanders Presence of 10 or more egg masses
    Spotted salamanders Presence of 20 or more egg masses
    Wood frogs Presence of 40 or more egg masses
  • A pool that has documented use in any given year by state-listed rare, endangered or threatened species that commonly require a vernal pool to complete a critical portion of their life-history is a significant vernal pool. Examples of vernal pool dependent state-listed endangered or threatened species include, but are not limited to, Blanding's turtles, Spotted turtles, and Bog haunter dragonflies.
  • Egg masses must be counted just past the peak breeding period of pool-breeding amphibians. Abundance of pool-breeding amphibians can only be used to determine the presence of a significant vernal pool during the identification period. The presence of fairy shrimp or a state-listed endangered or threatened species may be used to determine the presence of a significant vernal pool at times of the year other than the identification period.
  • Optimal times for counting egg masses of pool-breeding amphibians vary according to geographic location and weather . For instance, during cold springs, breeding can begin as much as 2 weeks later than it does in warm, wet springs. The optimal time to count masses is just past the peak breeding period. For wood frogs, this occurs approximately 2 weeks after they start full choruses. Wood frog egg masses hatch very quickly and are more difficult to count much past peak breeding. Salamanders do not have one peak; they often take 4 to 6 weeks to complete egg-laying. Furthermore, their egg masses do not hatch quickly and can be surveyed later than those of wood frogs. The following are guidelines for optimal times for counting egg masses:
    Geographic Region Wood Frogs Spotted & Blue Spotted Salamanders
    Northern Maine May 5 May 20 May 15 June 5
    Central Maine April 25 May 10 May 5 - May 25
    Southern Maine April 10 April 25 April 20 May 10

The Northern Maine region is considered to be approximately that part of the state north of a line extending from Fryeburg to Auburn to Skowhegan to Bangor to Calais. Similarly, the Southern Maine region is considered to be approximately that part of the state south of that same line.