Nowhere to Run
When a lake, river or stretch of swimming beach becomes polluted, we humans can avoid it. Other creatures don't have that choice. Frogs are coming to be seen as "sentinel" species: organisms that react early to environmental pollutants.
The skin of a frog is permeable: that is, the animal can breathe and drink through it. Frogs start life as eggs in water; most spend their early months as tadpoles, swimming in wetlands, ponds, and lakes. Water surrounds them.
Is It the Water?
In the mid-1990s large numbers of deformed frogs--including northern leopard frogs (Lithobates pipiens) and mink frogs (Lithobates septentrionalis) with extra legs--began turning up in water bodies around the upper American Midwest. Ordinary frog populations may include as many as 5 percent malformed animals, but in some midwestern ponds the rates were several times that high. The causes remain uncertain, but they may include parasites, chemicals in the water, or interactions between these factors.
Water is the ultimate sink for chemicals, including weed killers, pesticides, and fertilizers. Recently, some scientists have found links between a widely used weed-killer found in some North American water bodies and reproductive abnormalities in frogs. Their experiments have shown that as little as one part per billion of the weed-killer in the water shrinks the voice box--or larynx--of male Xenopus laevis. Male frogs use their calls to attract females, so whatever alters the voice box could affect reproduction. Scientists continue to examine the evidence for links between chemical water pollution and the worldwide amphibian decline.
Antibacterial soaps aren't any better than ordinary soap at preventing household illnesses. Traces of antibacterial soap in the water could even help create strains of resistant bacteria. So--why use them?