Amphibians

Woodhouse Toad

NPS VIP Carla DeKalb

The semiarid environment of the Colorado National Monument may seem like an unusual place to find amphibians, but in fact, there are several species of frogs, toads, and a rarely seen salamander that reside in the monument. Some amphibians have the ability to remain dormant in underground burrows, sometimes for more than a year, enabling them to survive in harsh, dry environments.

During the rainy season, amphibians emerge from their burrows to take advantage of intermittent streams and potholes. Male toads and frogs vocalize in the evenings, sending trying to attract mates in order to reproduce while the conditions are optimal. Rain fuels ephemeral streams and pools, which the frogs and toads need in order to lay eggs.

The woodhouse toad is one species that buries itself in the mud to escape the worst of the heat. In the evening, it emerges to seek mates and hunt for insects, scorpions, and small invertebrates. These toads have a distinct white stripe down their back that makes them easier to identify. Males are typically smaller than females and have smoother skin. Females lay up to 25,000 eggs in long, gelatinous strings.

 

Red-spotted Toad

NPS VIP Carla DeKalb

Another toad species that is well adapted to a desert environment is the red-spotted toad. They can lose up to 40% of their body water and still survive. This adaptation allows the toads to travel further from water and to survive longer away from it. They hunt mainly for insects, but will sometimes add smaller amphibians to their diet.

Listen for their distinctive trilling call, which lasts 4-10 seconds. During the mating season, males wrestle each other to establish territory. Females lay individual eggs, instead of in strings or clumps, and the tadpoles can metamorphose in as little as one month.

To avoid the heat, red-spotted toads look for cool, shaded crevices in rocky areas to spend the day. The best time to hear them is in the evening, after they emerge to hunt and look for mates. You can easily identify these toads by their distinctive red spots.

 

Red-spotted Tadpoles

NPS VIP Carla DeKalb

Whether eggs are laid in strings or are deposited one by one, most of the frogs and toads in the monument are dependent on the perennial streams and pools that form after rain or snowmelt. In other parts of their range, toads take advantage of stock tanks to lay their eggs. Mating is sometimes delayed until rain brings enough water to fill seasonal pools.

Once the eggs hatch, it can take a surprisingly short amount of time for a baby toad to undergo metamorphosis and become an adult. Spadefoot toad tadpoles can develop into adults in just two weeks. Other species, like the red-spotted toad and canyon tree frog, take up to four weeks. This rapid development is an advantage for survival when a toad or frog lives in an arid environment.

Tadpoles are dependent on the pools where the eggs are laid, because they use gills to breathe and mostly feed on algae. Flash flooding, pollution, and predators are all obstacles that tadpoles must overcome in order to survive. They are on a race against time to develop into adults before their seasonal pools dry up. Most won't make it to adulthood, which is why frogs and toads lay anywhere from 100 to 25,000 eggs at a time. Many predators eat frogs and toads in all of their life stages, including birds, foxes, coyotes, other tadpoles, snakes, and lizards.

If a toad survives to be an adult, they have strategies to get through the times when their seasonal pools dry up. Some species dig holes and bury themselves, waiting for the water to come back. The spadefoot toad is well known for doing this, and remains underground for up to ten months before re-emerging to look for mates.

 

A Woodhouse Toad in the Grass

NPS VIP Carla DeKalb

Amphibians are very sensitive to changes in their terrestrial and aquatic environments. Like the canary in a coal mine, amphibians are considered indicator species that serve as monitors for the environment. Over the last several years scientists have documented an alarming decline in amphibian populations, some to the point of extinction. While a specific reason for this trend is unknown, there are several possibilities being studied. Pollution, acid rain, global warming, loss of habitat, and non-native predators / competitors are just a few of the changes that may be causing the declining populations.

You can help protect the monument's amphibians by staying out of the seasonal pools and streams in the monument. Amphibians are sensitive to lotions that we use on our skin, such as suntan lotion, and keeping those products out of the pools and streams is very helpful. Eggs and tadpoles can be injured by people walking in pools. Help these critters have the best chance of survival by hiking with care.

 

Canyon Tree Frog

NPS Photo by Katharine Lynch

Amphibian Species List

All of these species have been found in the monument, although some are less commonly seen.

Red-spotted Toad (Bufo punctatus)
Woodhouse's Toad (Bufo woodhousii)
Canyon Treefrog (Hyla arenicolor)
Northern Leopard Frog (Rana pipiens)
Great Basin Spadefoot Toad (Spea intermontana)
Tiger Salamander (Ambystoma tigrinum)