Natural Area Preservation

Wood Frog

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Rana sylvatica

Identifying Features

  • 2 to 2.5 inches long; dark mask through its eye and a white stripe on the upper lip.
  • Fairly common in wooded habitats.
  • Adults are rarely found in water except during breeding.
  • Will migrate across open areas to reach suitable breeding ponds, but otherwise remain under tree canopy.
  • Hibernate on land beneath loose soil, leaf litter, or decaying logs.  Survive periods of sub-freezing temperatures by producing large amounts of glucose, causing ice to form in the extra-cellular spaces rather than within the body cells.
  • Tadpoles approaching metamorphosis develop poison glands to repel aquatic insect predators, although biggest threat to tadpoles is ponds drying before transformation is complete.
  • Adults have toxic skin secretions, which repel shrews, but not snakes, other amphibians or birds.

Call

  • Squawking, duck-like call.

Breeding

  • Vernal ponds, floodings, wooded swamps, and backwaters are used for breeding. 
  • Breeding season is usually only 1-2 weeks long, in mid to late March or early April.
  • Females deposit from 500 to over 3000 eggs in one or many gelatinous masses, usually attached to plant stems, or twigs near the surface. 
  • Communal egg laying is common to aid in maintaining moisture and temperatures and reducing predation.

Development

  • Egg incubation period is temperature dependent, ranging from four days to four weeks.  Transformation occurs in 6-15 weeks.
  • Large numbers of froglets disperse into surrounding woods from late May through early July.
  • Males reach sexual maturity in 1-2 years, females in 2-3 years.

Habitat Type

  • Permanent wetlands.
  • Forests.

​​Natural Area Preservation
Office:
3875 E. Huron River Dr.
Ann Arbor, MI 48104
734.794.6627

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Dave Borneman
  Deputy Manager
Tina Stephens
  Volunteer & Outreach Coordinator
Becky Gajewski
  Stewardship Specialist
Michael Hahn
  Stewardship Specialist