Frogs and the Ecosystem

Over the past 50 years, scientists have recorded major declines in frog populations around the world. A few species have vanished completely. Many frog die-offs are the result of local human activity, but the epidemic has also reached remote areas. Is there a global cause? Scientists continue to search for answers.

americantoad_harding_med.jpg

 © James Harding, MSU

American toad, Bufo americanus. with throat pouch inflated

Major causes of frog declines:

  • Habitat destruction
  • Introduced species
  • Chemical pollution
  • Climate changes
  • Over-collection
  • Epidemic diseases

Frogs with extra or missing legs, eyes, and toes have been found in 44 states since 1996. Possible causes include parasites, pollution, and ultraviolet radiation.

In a laboratory study in 1997, nearly half of the frog eggs exposed to ultraviolet light grew into malformed adults, while eggs with no exposure developed into normal adults.