Global Amphibian Declines

Something mysterious is happening to the world's amphibians--their numbers are declining!! During the past number of decades, scientists have become concerned about the alarming number of reports of amphibian populations declining or vanishing entirely. This was often a result of the direct impact of human activities in that particular area.

Then, in the mid-eighties something new happened in the mystery--scientists became especially troubled because populations declines were documented in wilderness areas, with little or no human disturbance. Both the Gastric Brooding Frog of Australia (in photograph to the left) and the Golden Toad of Costa Rica have disappeared from relatively untouched, or pristine, places. The Gastric Brooding frog had a unique characteristic of swallowing the fertilized eggs and allowing them to develop in its stomach into froglets. Somehow the adult frog was capable of switching off its gastric juices, preventing the eggs from being destroyed by the juices of the stomach. Pictured here is a froglet emerging from an adult frog. (Photograph from FROGLAND web site.)

Click below to view a list of:
Amphibian and Reptile Diversity and Distribution in the United States
Amphibians of the Upper Midwest and Eastern Plains
Threatened and Endangered Frogs and Toads

What Scientists are saying about
Global Amphibian Population Declines

Research into the cause or causes of Global Amphibian Population Declines is now a very high priority for scientists all over the world. Suggested causes include:

  • loss of important habitat. This factor is still extremely important in population declines of most animals. In many cases, habitat may not be destroyed completely, but only fragmented, making it difficult for the frogs to get to breeding ponds. For example, some species of frogs only go to ponds to lay eggs and breed, spending the remainder of their life in wooded or prairie areas. If a road is placed in between the ponds and the woods or prairie, the frogs may not be able to get to the breeding ponds.
    Click here to read more about what's being done to protect the habitat of the endangered California Red-legged Frog.
  • increasing ultraviolet radiation. In the early to mid-eighties, scientists began to notice a thinning of the ozone layer, resulting in an increase of ionizing radiation (UV-B). Because amphibian skin is sensitive, this was seen as a possible cause of declines.
  • pollution by chemicals. The impact of acid precipitation, fertilizers, pesticides and herbicides on the environment and directly on amphibians. Click on Weird Frogs, Chemicals Linked to read more about pesticides.
  • introduction of non-native competitors and predators into amphibian environments.
  • pathogens. Attack from either new pathogens or existing pathogens which could kill amphibians weakened by some of the other possible challenges listed above. Read more about a newly discovered fungus that is causing amphibian declines.
  • parasites. Trematode cysts are found to cause damage to developing limb buds, which can result in the growth of extra limbs.

However, most scientists assume that frog declines can somehow be related to humans and their increasing demands on the environment.

Read recent information on the world's disappearing amphibians from the Institute for Agriculture and Trade Policy (IATP).

Sehoya Harris is a conservation biologist who has studied frogs as well as coyotes and red wolves. For her frog studies she has spent three years in the rain forests of Ecuador in South America. In 1997 she attended the third World Congress of Herpetology and discussed the results of A Thousand Friends of Frogs and the involvement of students and citizens with the other scientists. Click here for her report.

To get more information on the global situation, a group of scientists formed the Declining Amphibian Populations Task Force. Visit the web site for more information on this group and their newsletter FROGLOG.

What Scientists are saying about
Amphibian Population Declines in Minnesota

John Moriarty, Wildlife Specialist and Scientific Advisor to the project, reports on the Status of Amphibians in Minnesota.

Recently at the 1998 MidWest Declining Amphibians Conference, Minnesota scientist, Dr. David Hoppe from the University of Minnesota- Morris made a surprising and distressing statement about frog populations in some areas of Minnesota. He visited 14 sites which another herpetologist, David Merrell, has collected frogs from during the 1950's. In 1997, Dr. Hoppe found frogs only in five of the sites!!!


Help Survey Amphibian Populations in Minnesota
through the MN Frog and Toad Calling Survey


What is Being Done About Amphibian
Population Declines in Other States

Click on the following organizations or news articles to find out what is being done to protect amphibian populations:

Earthjustice Legal Defense Fund, California
Ohio State University, Ohio
Washington University, Missouri
"Amphibian Assault," Environmental News Network (1997)

Choose from these other areas:
Amphibian Facts
MN Frogs and Toads
Malformed Amphibians
MN Frog Watch
Surveying Populations
Malformed Amphibian Photos
Student and School Reports
FAQ's

 

 

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