When you look around at the arid landscape of Petrified Forest National Park, it's hard to imagine that animals which require consistent moisture could possibly thrive here. But they do. Three hundred and fifty million years ago, the first fish-like amphibians hauled themselves out of the sea. By the time dinosaurs appeared on the scene, amphibians were already flourishing. Today, toads and one species of salamander are the primary representatives of ancient amphibians at the park. Toads survive in arid climates because of their permeable skin. Amphibians do not drink water, they absorb it. Most terrestrial amphibians like the toad have an area of skin called the pelvic patch. This thin patch has a network of capillaries which absorb moisture from the environment. The downside of permeable skin is that what is easily absorbed is also easily lost to evaporation. Burrowing into moist earth provides some protection, but "desiccation," or drying out, is a common life-threatening problem in arid climates.
Amphibians have two life stages: a larval, aquatic form called tadpole and an adult, terrestrial form. Breeding, as well as toad choir practice, usually occurs on spring and summer nights after significant rainfall. Male toads do the vocalizing. Females lay long strings of gelatin-covered eggs in pools of water. Because the wet environment is transitory, toad reproduction can be fast and furious. Depending on the species, the eggs may hatch within hours. Metamorphosis from a water-based to a land-based creature does not take long, varying in time depending on species. Because of the hydration properties of the pelvic patch, toads do not need to live near water. They tend to range further from the water's edge than their relatives and are better suited for an arid lifestyle.
Although amphibians have survived here for millions of years, today they are in trouble. Biologists around the world have noted dramatic declines in amphibian populations. No one knows what is causing these declines, but it is thought to be a sign of unfavorable environmental changes. Habitats such as wetlands are being destroyed, pesticides and metal poisons are contaminating the water, new predators are being introduced, the ozone layer is being depleted, and global climate changes are underway. In some cases, natural population fluctuations may explain the decline but scientists have ruled out natural causes as the only explanation for the overall problem. All around the world, declines are occurring in many species. What is clear is that human actions are the primary cause of these declines.