You may have read about the decline of global amphibian populations due to disease, pollution, climate change, or other causes. When trying to determine the exact factors involved in the decline of certain species or populations, scientists might find confounding factors at play which may paint a picture of overall environmental decline. Pinpointing these factors is by no means an easy task as so many factors could be involved in species decline. This appears to be the case for frogs with irregular, missing, or extra limbs. The first known report of deformed frogs was in the summer of 1995 at a pond in Southern Minnesota. The discovery was made during a field trip by a group of school children and this ushered in similar discoveries across the United States and Canada and across various amphibian taxa (primarily amphibians from the order Anura i.e. frogs and toads). These deformities are generally reported in newly metamorphosed individuals which suggests reduced survival of deformed adults.
Scientists studying this phenomenon believe a multitude of factors such as parasitic trematode (flatworm) infestation, pesticides, insecticides, other chemical agents, and habitat degradation could be involved in amphibian deformities. Life history questions still need to be answered, such as the role of stress in development, that might shed light on the issue. A baseline for deformities is also unknown. Has this always occurred and we are just now noticing it? As scientist study how pesticides and other potential causes impact amphibian development one thing that is becoming abundantly clear is how vulnerable these animals are to the world around them.
About this illustration: If you Google images of frog deformities you will come up with image after image of all manners of deformities. It is pretty clear that this is a serious issue and I did not feel the need to play up the image. Expect to see more environmental/ animal health posts in the future. This image is available via Redbubble.
For More Information:
Malformed Frogs in Minnesota: An Update: http://pubs.usgs.gov/fs/fs-043-01/
Amphibian Malformation Page: http://www.colorado.edu/eeb/facultysites/pieter/amphibianmalformations.html
Introduction to the Malformed Amphibian: http://ces.iisc.ernet.in/biodiversity/amphibians/link3.htm