Plants and Animals

Pseudacris maculata Boreal chorus frog

species photo
Tom R. Johnson

Key Characteristics

The Boreal Chorus Frog is a small, brown, reddish, tan, gray or olive frog (adult length 1.9-3.8 cm/0.75-1.5 in) with three dark, sometimes broken, stripes on its back. The Boreal Chorus Frog lacks dorsolateral folds on its back. There also is a distinctive white or cream-colored stripe along the upper lip bordered above by a dark stripe from the nostril through the eye and along the side of the body. The breeding call of a Boreal Chorus Frog is a short, rising, scratchy "cree-ee-ee-ee-eek" which has been compared to the sound made when running a thumbnail down the teeth of a fine-toothed comb. The Boreal Chorus Frog has shorter hind legs, greenish back stripes and a longer and slower breeding call than the Western Chorus Frog.

Status and Rank

US Status:
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: S1 - Critically imperiled

Occurrences

CountyNumber of OccurrencesYear Last Observed
Keweenaw11964

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

In Michigan, the Boreal Chorus Frog is known only from Isle Royale in Lake Superior where it primarily occurs along the island’s rocky shoreline/bedrock lakeshore and adjacent boreal forest as well as some inland bogs and swamps. The species breeds in small pools filled by rain or waves along the shoreline. When the Boreal Chorus Frogs are not chorusing or laying eggs, they are presumably in the boreal forest, probably within a few hundred meters of the breeding pools. Chorus frogs tend to remain near their breeding sites year-round, spending most of their time hidden beneath logs, rocks, and leaf litter or in loose soil or animal burrows. They hibernate in these places as well.

Specific Habitat Needs

Downed woody debris needed in: BogBoreal forest.

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

Maintenance and protection of breeding pools and adjacent forested or open habitat are essential for management and conservation of the Boreal Chorus Frog. The areas in which Boreal Chorus Frogs have been documented should be monitored and maintained. Connectivity between breeding pools/ponds and adjacent forested or open habitats should be maintained. If timber harvesting is going to occur in forested habitats adjacent to breeding ponds, partial harvest techniques should be employed to maintain cool, moist microclimates. A natural forest buffer of 30 m (100 feet) or more or at least the width of local tree heights should be maintained around breeding ponds if possible. The use of herbicides, pesticides or other related chemicals should be limited or avoided in Boreal Chorus Frog habitat, especially near breeding sites. Woody debris, rocks, leaf litter and other cover objects should be maintained to provide habitat for this species.

Active Period

Breeding from first week of May to second week of July

Survey Methods

The best way to survey for Boreal Chorus Frogs is to listen for breeding calls from adult males during the breeding season. In the spring, adults will congregate at breeding ponds and begin calling as soon as most of the snow has melted. Although Boreal Chorus Frogs on Isle Royale can breed and lay eggs from May through early July, the best time for conducting frog call surveys appears to be in May. Call surveys can be conducted in the evening or at night but also during the day. Visual encounter surveys also can be conducted for adult Boreal Chorus Frogs and their tadpoles at breeding sites in the spring and summer from May until mid-July to mid-August.

Breeding call surveys

Survey Period: From first week of May to fourth week of May

Time of Day: Evening
Humidity: Humid
Cloud Cover: Overcast
Air Temperature: Warm
Wind: Light Breeze

Time of Day: Night
Humidity: Humid
Cloud Cover: Overcast
Air Temperature: Warm
Wind: Light Breeze

Visual encounter survey

Survey Period: From first week of May to third week of August

Time of Day: Daytime
Air Temperature: Warm

References

Survey References

  • Heyer, W.R., M.A. Donnelly, R.W. McDiarmid, L.C. Hayek, and M.S. Foster, eds. 1994. Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians. Smithsonian Institution Press, Washington D.C. 364pp.
  • Karns, D.R. 1986. Field Herpetology: Methods for the Study of Amphibians and Reptiles in Minnesota. Occ. Pap. No. 18. J.F. Bell Museum of Natural History, University of Minnesota, Minneapolis.

Technical References

  • Harding, J.H. 1997.Amphibians and Reptiles of the Great Lakes Region. The University of Michigan Press, Ann Arbor. 378pp.
  • Kingsbury, B. and J. Gibson, eds. 2002. Habitat Management Guidelines for Amphibians and Reptiles of the Midwest. Partners in Amphibian and Reptile Conservation. 57pp.
  • Smith, D.C. 1983. Factors controlling tadpole populations of the chorus frog (Pseudacris triseriata) on Isle Royale, Michigan. Ecology 64(3):501-510.
  • Smith, D.C. 1987. Adult recruitment in chorus frogs: effects of size and date at metamorphosis. Ecology 68(2):344-350.