Amphibians in the Desert: Frogs, Toads and Salamanders of Glen Canyon

Frogs, toads and salamanders lead "double lives" — the word amphibian comes from the Greek for "having two lives." A larva, such as a tadpole, becomes an adult that often looks nothing like it. Amphibians eat insects and other invertebrates and are eaten by fish, reptiles, birds and mammals, and because they are sensitive to pollution, habitat loss and disease they are good indicators of environmental change.

Nearly all amphibians breed and develop in water, and with their moist skin they can die of drying out. Lake Powell is one of the largest reservoirs in the country, but a short way from its shore Glen Canyon National Recreation Area is hot, dry desert. How do amphibians manage there?

A canyon treefrog (Hyla arenicolor) camouflaged on sandstone. NPS.

Threats

Flooding, fire, debris flows and grazing; loss of water; habitat cut into isolated pieces; introduced plants; non-native bullfrogs and crayfish; predatory fish; and disease. Loss of water is a serious threat in a place as dry as Glen Canyon.

The assessment

A Park Service Natural Resource Condition Assessment (NRCA), which evaluates the condition of a park's natural resources so it can manage them with the best available science, took amphibians — above all the northern leopard frog — as one of its focal resources.

Who lives there

Three more may occur: the American bullfrog, the Great Plains toad and the plains spadefoot. All are native to the United States, but the bullfrog was introduced to the West and counts as non-native at Glen Canyon, where it eats and competes with native amphibians.

They breed in slow side channels, isolated pools, springs and tinajas (rock water pockets). Outside the breeding season, adults of every species except the bullfrog and the leopard frog aestivate — lie dormant through heat and drought — underground, in rock crevices or other damp, dark places; those two need water all year. Amphibians have been confirmed in six of the recreation area's eight watersheds.

An eastern tiger salamander at home in the desert. NPS.

The northern leopard frog

The leopard frog ranges across the northern United States and Canada and south into Nevada, Arizona and New Mexico, and over the last 60 years it has declined in many parts of that range. Utah and Arizona wildlife agencies treat it as a priority. At Glen Canyon it is uncommon. Utah State University ecologists gathered data on where amphibians and frogs occur, breeding, disease, and how thickly wetland plants cover breeding pools.

A northern leopard frog, photographed at Gavins Point National Fish Hatchery, Yankton, South Dakota. U.S. Fish and Wildlife Service / Sam Stukel.

• Where it lives. It was recorded at 29 locations in Glen Canyon between the mid-1950s and 2019. It is gone from at least 17 — many flooded by Lake Powell — and its status at 8 is unknown. It is known at 4 sites today, in the Escalante and Upper Lake Powell watersheds. Surveys were neither systematic nor widespread, but the occupied area has clearly shrunk over the last 70 years.
• Breeding. Yes: the Arizona Game and Fish Department found evidence of breeding at most occupied sites in any given year.
• Disease. None of 74 leopard frogs and 5 other frogs tested from 2007 to 2019, in four drainages, carried the fungus that causes chytridiomycosis, a serious amphibian disease.
• Reeds. Common reed (Phragmites australis) can choke the open water of breeding pools. Wetland plant cover at some occupied sites rose significantly — 385% from 1995 to 2017 — but whether reed or other plants caused it is unclear.

Next steps

The assessment recommends monitoring amphibians by four indicators: community makeup and breeding, water quality, non-native species, and disease. For the leopard frog in particular: survey the 8 sites of unknown status; watch for loss of water; survey vegetation such as Phragmites at known sites; and monitor water quality, especially in breeding pools, for airborne contaminants such as heavy metals and nitrogen. The Park Service, the Arizona Game and Fish Department and the Grand Canyon Wildlands Council have built breeding pools to reintroduce leopard frogs at one site.

Woodhouse's toad. NPS.

What you can do

• Leave leaf litter, rocks, logs or a water source in your yard for hiding places, insects and clean water.
• Keep dogs and cats from disturbing amphibians and other wildlife.
• Keep water clean — amphibians absorb chemicals through their skin.
• Watch and listen, but leave them be. Frogs make great sounds.

Sources

• National Park Service, "Amphibians in the Desert," in the series NRCA 2022: Condition of Glen Canyon's Tributary Rivers and Associated Resources. https://www.nps.gov/articles/000/nrca_glca_2021_amphibians.htm
• J. Albright and others, Natural Resource Conditions at Glen Canyon National Recreation Area, Natural Resource Report NPS/SCPN/NRR—2022/2374. https://doi.org/10.36967/nrr-2293112
• Corrected: the page places Gavins Point National Fish Hatchery in "Yukton"; the town is Yankton.