Can you imagine living underground for nine months of the year and not eating, drinking, or defecating? Amphibians are amazing animals that do just that!
It is hard to imagine that in this dry region animals requiring consistent moisture could thrive. Three hundred and fifty million years ago the first fish-like amphibian hauled itself out of the sea. Fossilized remains of giant amphibians, such as metoposaurs, have been discovered within the sedimentary rock of the park. By the time dinosaurs appeared, amphibians were flourishing. While much smaller, we still have amphibians in the park today.
How have they survived and adapted to 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. Such behavioral and physiological mechanisms shape their daily life and make it possible for them to survive.
The spadefoot toad is a great example of adaptation to this semi-arid environment, by burrowing underground using the specialized “spades” on its hind feet. It spends most of its life underground in earth-filled burrows, active only during the monsoon during which they mate. Spadefoot skin secretions smell like peanuts, probably to irritate predators.
Although amphibians have survived on Earth 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 planet-wide problem. All around the world, declines are occurring in many species.
Amphibians recorded in the park
Continuing research—such as nocturnal road surveys—enables us to increase our knowledge about the park and its inhabitants.