Natural History - Amphibians
One type of animal you probably will not spot very frequently in the Glen Canyon NRA is an amphibian. The desert does not provide a very inviting climate for animals like amphibians that require high amounts of moisture for survival and reproduction.
Amphibians are cold-blooded, meaning that they regulate their body temperature through external sources rather than internal metabolism. They have moist, soft skin that aids in temperature, moisture, and gas regulation. Because of this, they cannot be exposed to extreme heat or drought, both of which are common to the desert. Most amphibians in Glen Canyon are found in or near water sources.
Another reason you might not see many amphibians in Glen Canyon is that they are primarily nocturnal. In order to conserve energy and moisture, most amphibians are active during the early morning, late evening, or at night. During the day they spend their time in shady cracks in the rock, underground, or in other dark, moist places.
At least six species of amphibians live in Glen Canyon, but other species may eventually be found with more surveys in the vast landscape of Glen Canyon. The Arizona tiger salamander is the lone salamander species. This salamander can occasionally be found around pools and under logs and litter in wetter side canyons off Lake Powell. The larval form of tiger salamanders is also often used as bait at Lake Powell by fisherman, and can sometime escape. There are two types of frogs, the northern leopard frog and the canyon treefrog. The leopard frog is a large, green frog with spots that was once common along the Colorado River through Glen Canyon, but has been pushed up into the side canyons by the rising waters of Lake Powell. Currently about eleven populations are known in Glen Canyon NRA. This species is declining throughout much of its range in North America. Canyon tree frogs are common around the shores of Lake Powell and in the side canyons, where they can often be found clinging to sandstone walls near water. This species can be identified by its small size, grayish somewhat warty skin, and toe pads.
Two different groups of toads occur, true toads and spadefoot toads. The true toads include the red-spotted and Woodhouse’s toads. Woodhouse’s toads are typically larger than the red-spotted, and can be distinguished by the white stripe on their back and the oval glands behind the eyes. The red-spotted toad lacks the white stripe and has round glands. These species are most common along streams in side canyons, but can also be found occasionally crossing the desert as they move between canyons and waterholes. Spadefoots are represented by the Great Basin spadefoot. Spadefoot toads are different than regular toads in that they have vertical pupils (true toads have horizontal pupils), lack the glands behind the eye, and have a spade-like structure on the inner surface of their hind foot that is used to dig burrows. They remain buried in mud at the bottom of dried up pools or washes, and only emerge during heavy rain events. They are particularly stimulated by the sound of thunder coming from late summer rainstorms.
Even if you are not fortunate enough to see any amphibians while in the desert, you will probably hear them. If you are close to a water source at night and you hear something in the distance that sounds like the bleat of a sheep with a cold, it could be a canyon treefrog. A hoarse snoring sound could be the call of a Woodhouse’s toad, while a high musical trill advertises the presence of a red-spotted toad. Even more interesting are the calls of leopard frogs, which include a wide range of sounds from odd chuckling and grunting to high thin squeaks that are similar to the sound made by rubbing your hand over an inflated balloon.
John Spence, Ecologist, Glen Canyon National Recreation Area