Goals & Methods

Eastern newt at Graves Farm © A.C. Brown
Eastern newt at Graves Farm © A.C. Brown

The goals of our amphibian surveys are to:

  • Enhance our knowledge about the diversity and abundance of amphibians on our wildlife sanctuaries, particularly those of conservation concern.
  • Use current distributions and abundances of amphibians on our wildlife sanctuaries as a basis for comparison with any future changes.
  • Determine if there are any management measures we could be taking to enhance our wildlife sanctuaries as habitats for amphibians.


The amphibian monitoring on Mass Audubon wildlife sanctuaries includes three different types of data collection, designed to detect long-term changes in amphibian populations:

  • Egg mass counts in vernal pools
  • Coverboard surveys for amphibians in forests
  • Calling surveys

These methods provide an index that can be used for comparing present and future abundances (not an absolute number).

Egg mass counts in vernal pools

As of 2013, we have been carrying out egg mass and tadpole surveys at 31 vernal pools in 11 wildlife sanctuaries. As part of a Spadefoot Toad Reintroduction Project, an additional four vernal pools are being monitored at Ashumet Holly Wildlife Sanctuary and 5 restored pools at Long Pasture Wildlife Sanctuary. Surveying takes place annually and begins in early spring (late March through early April) as soon as wood frogs or spotted salamanders have started breeding.

  • Ideally, each vernal pool should be visited three times: just after it thaws, 10 days later, and a month after that.
  • When not feasible, the sampling should take place when egg masses of both wood frogs and spotted salamanders are present (normally between April 1 and 15).
  • Pairs of observers walk around the periphery of a vernal pool and record:
    • the number of egg masses by species
    • the approximate number of eggs per mass
    • the stage of development.
  • Water depth is also taken to help determine the amount of time the pool holds water (known as hydroperiod).

Coverboard surveys for amphibians in forests

Coverboard installation for amphibian monitoring

Coverboards are artificial sampling units made of flat wooden boards that are placed on the forest floor. They provide a non-destructive, statistically valid way to sample terrestrial amphibians over the long term. Salamanders and other animals use coverboards for a moist shelter just as they might use leaf litter or logs.

Wachusett Meadow Wildlife Sanctuary has been sampling coverboards since 1999. We began installing coverboards at other wildlife sanctuaries in 2008 and as of 2011 we have coverboard monitoring at 12 wildlife sanctuaries.   

  • Two-inch thick untreated pine boards cut into 1 ft squares (30x30x5cm) are placed down in pairs along transects, spaced about 3.3 ft from each other. 
  • Each pair is spaced a minimum of 20 feet from the next pair. Typically we have 20 pairs of boards per sampling area.
  • Sampling takes place twice a month in April and May, once a month from June-August, and twice a month from September through November.
  • Each coverboard is lifted up and the number of salamanders found underneath are counted.
  • Also recorded: other organisms we find under the board, such as frogs, snakes, insects, etc.

Frog calling surveys

Male frogs call from ponds and wetlands in order to attract mates. Keeping records of this activity helps determine the presence of different frogs within wetlands. The intensity of sound gives some idea of their abundances, while the timing of calls is one of the parameters that can indicate climate change. 

The U.S. Geological Survey has developed the North American Amphibian Monitoring Program, a citizen monitoring program based around detecting frog calling. 

  • Sampling takes place early spring, late spring, and early summer (during 5 different days for each period) to insure recording different species. 
  • Ideally, counts begin 30 minutes after sunset and ends before 1 a.m.
  • The listener goes to the site, waits 3 minutes quietly for the frogs to settle down from any disturbance caused by the observer, then listens for 5 minutes.
  • The listener records the species that are calling and the intensity of the calls (using a standardized code - full chorusing, somewhat overlapping calls, or distinct individual calls), before proceeding to the next site.

Recognizing that it may be difficult for sanctuary staff to be available after dark, we have developed a simple protocol to allow staff to record frog calls in the course of their work around a sanctuary. The listening procedure is the same as described above, however sampling can take place any time during the day. Such information will still give us presence/absence of different frogs on a sanctuary.

For more specific details on our amphibian sampling protocols, contact the Inventory Monitoring Project Coordinator.