At our house, a trip down the hill to the pond is always prefaced by the announcement that we are “doing a little frog work.” It’s a reference to Russell Hoban’s Best Friends for Frances, in which Frances’ friend Albert announces that he is off to do “a little frog work,” indicating that it’s a boys-only activity. By the end of the story, there’s been some learning about who’s qualified to do frog work and what friendship means among peers and siblings.
Anybody can do frog work, and back in 1995 some middle school students in Minnesota noticed some things in frogs that weren’t quite right. The frogs they found had extra legs, or no legs, or eyes in the wrong place. The Environmental Protection Agency took notice. Eighteen years later, deformed frogs are turning up all over the world, and scientists are still trying to determine what’s causing the deformities in the ones in Minnesota.
Pieter Johnson of the University of Colorado thinks the main culprit in North American frogs is a parasite called Ribeiroia ondatrae. While his research shows that the parasites are more common in man-made water habitats, it still isn’t clear what it is in those habitats that cause the parasites to thrive and proliferate, decimating the vulnerable frog population. ”We are running experiments looking at shifts in temperature, runoff of nutrients and pesticides, and biodiversity loss to evaluate their potential influence,” Johnson told PBS Newshour. What Johnson does know is that the parasites first infiltrate snails and then are released into the water where they seek out the tender flesh of tadpoles. Wherever they burrow into the skin of the tadpole is where the deformity begins. The tadpoles simply grow around the obstruction caused by the parasites, which is why legs and eyes appear in the wrong place or not at all.
The malformations make the frogs less agile and easy prey for birds, who ingest both frog and parasite. The parasites then use the bird as a host and infect other waterways through their droppings. A complete photo gallery of the deformed frogs studied by Dr. Johnson can be found here.
But parasites are not the only explanation, and back in Minnesota the US Geological Survey and the Department of the interior say,
It is likely that one or more combinations of chemicals, biological, and physical factors are responsible for causing the malformations in Minnesota frogs (Fort and others, 1999; Burkhart and others, 2000; Lannoo, 2000). Chemical combinations may be mixtures of natural and human-made organic chemicals, each of which is harmless on its own but toxic when combined (Burkhart and others, 2000). The number of possible combinations of chemicals, biological, and physical factors is enormous, which may explain why finding the causes for frog malformations has been a difficult task.
While parasites clearly cause some or most of the malformations at some sites, that’s not true at all sites, so interdisciplinary teams of scientists are pulling together to figure out the mystery.
The research continues, and it was all set into motion by kids on a field trip, noticing frogs. Tumblehome Learning‘s Something Stinks! is a fictional story of kids doing the same thing – finding adventure in science in their own community. Emily Sanders sees, and smells, that something isn’t right in the local river, and enlists her friends and family in getting to the bottom of the mystery.