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.  They can survive sub-freezing temperatures by making large amounts of glucose. This causes 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. Their biggest threat, however, is ponds drying before transformation is complete.
  • Adults have toxic skin secretions, which repel shrews, but not snakes, other amphibians or birds.


  • Squawking, duck-like call.


  • 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. These are usually attached to plant stems ​or twigs near the surface. 
  • It is common for more than one frog to lay eggs in the same spot. This helps maintain moisture and temperatures and reduce predation.


  • Egg incubation ​depends on how hot or cold it is, ranging from four days to four weeks.  Transformation occurs in 6-15 weeks.
  • Large numbers of froglets disperse into the​ 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
3875 E. Huron River Dr.
Ann Arbor, MI 48104

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Remy Long​
  Deputy Manager
Tina Stephens
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Becky Hand
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Michael Hahn
  Stewardship Specialist