an immature Scaphiopus couchii
Can you imagine living underground for nine months of the year and not eating, drinking, or defecating? Amphibians are an amazing group of animals do just that.
It is hard to imagine that in this dry region animals that require consistent moisture could thrive. Three hundred and fifty million years ago the first fish-like amphibian hauled itself out of the sea. Within the sedimentary rock of the park, giant amphibians such as metoposaurs have been discovered as fossils. By the time dinosaurs appeared, amphibians were flourishing. Today, they are still among the most successful groups of animals.
Why have they survived and adapted to such varied environments worldwide? Permeable skin! Amphibians do not drink; they absorb water through their skin. Spadefoot toads, residents of the park, absorb water from the soil in which they hibernate. Although permeable skin allows for water absorption, it provides little barrier to evaporation. This causes the animal's water balance to be in constant flux. Evaporative water loss also results in loss of body temperature. This is why you often see amphibians on warm pavement in the evening. It is not an easy life for amphibians in this dry grassland. Behavioral and physiological mechanisms that shape their daily life make it possible for them to survive.
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.
The following is a list of amphibians known to currently occur in the park. Further research will undoubtedly locate more species as different habitats in the park are more thoroughly studied.
Did You Know?
Petroglyphs are sometimes calendars, marking events like the summer solstice with interactions between the glyph, the sun, and natural landscape features.