Alaska is situated to the far northwest of North America – it is a large state, thus boasting a variety of climates and habitats. In the extreme north of the state, the conditions are cold and dry with an Arctic climate, whereas central Alaska has a continental climate. Habitats that can be found here include mountains, glaciers, tundra, wetlands, rivers, lakes, and boreal forests.
Due to extreme cold during the winter and other harsh environmental conditions, only a handful of frogs can be found in Alaska. Most of them reside in the southern part of the state, although one, the wood frog, can be found further north due to having special adaptations enabling it to survive freezing temperatures.
Alaska Frogs
1) Wood frog (Lithobates sylvaticus)
- Native to Canada, Alaska, and the northern US
- Family: Ranidae
- Order: Anura
- Conservation status: Least concern
The wood frog grows to 7.6 cm (3 in) in length and ranges in color, with individuals being brown, rusty red, gray, or tan across the dorsum, while the ventral region is yellow or greenish-white. Two prominent dorsolateral folds run down the back from the eyes, and there is a black patch on the face.
This species can be found throughout Alaska and is the only species of frog that lives north of the Arctic Circle. This lifestyle brings with it a number of challenges, and the wood frog is specially adapted to survive in these harsh conditions – in winter, its body freezes. Research has found that Lithobates sylvaticus has biochemical adaptations for withstanding freezing conditions, with the activity of enzymes in the liver and leg muscles increasing in response to extreme cold.
As their name suggests, these frogs live in deciduous or coniferous woodland – often favoring upland habitats during winter. During breeding season, individuals travel to ponds and pools, where the females lay eggs in masses. The growth of the eggs is affected by water temperature, with at least 50% surviving if temperatures are between 6 – 24°C (42.8 – 75.2°F).
2) Columbia spotted frog (Rana luteiventris)
- Native to the Pacific Northwest
- Family: Ranidae
- Order: Anura
- Conservation status: Least concern
The Columbia spotted frog ranges in length from 4 – 10 cm (1.6 – 4 in). These frogs have short hindlimbs and rough skin, and their dorsolateral folds are less prominent than in other species. The coloration of this species varies from pale to dark brown, and all individuals have black spots with lighter-colored centers. The underside is cream or gray, with salmon-colored skin on the lower abdomen and hind legs.
The distribution of this species in Alaska is likely confined to the southeast, where it resides in coastal forests and is rarely found far away from some form of permanent water body. During breeding season, these frogs are heavily reliant on dense vegetation in which they lay their eggs – this provides them with protection from predators and shelter from the elements.
The Columbia spotted frog is an opportunistic feeder, consuming a wide variety of invertebrates such as beetles, wasps, spiders, and flies. The main threats to this species include the destruction of wetlands and water contamination – it has been suggested that limiting livestock access to breeding ponds may enable populations to recover.
3) Northern red-legged frog (Rana aurora)
- Native to northern California, Oregon, Washington, and British Columbia
- Family: Ranidae
- Order: Anura
- Conservation status: Least concern
The northern red-legged frog is 4.4 – 7.6 cm (1.7 – 3 in) in length and has a slender waist, long limbs, and webbing on the hind feet. The skin is smooth and reddish-brown, gray, or olive in color, with black flecks on the back and sides. The legs have dark bands along them, and the hind limbs have red on the underside.
This species was introduced to Alaska from Washington in 1982, and its current range in the state is confined to Chichagof Island. Its preferred habitat is among emergent riparian vegetation near ponds or streams – this provides them with a means to escape from predators and a place to shelter and remain cool.
Due to being an invasive species, the northern red-legged frog may have a number of adverse effects on ecosystems in Alaska. The tadpoles consume algae and periphyton, which can affect the aquatic food web, and adults may compete with native species for resources.
4) Pacific treefrog (Pseudacris regilla)
- Native to the West Coast, all the way south to Baja California
- Family: Hylidae
- Order: Anura
- Conservation status: Least concern
The Pacific treefrog is small, growing to a length of 1.9 – 5.1 cm (0.75 – 2 in). It has rough skin that is green or gray in color, with numerous small dark spots across the back and sides. A dark brown stripe extends from the snout, through the eyes, and down to the shoulder, and the front limbs are slightly yellow in color. This species can change color to match its environment, a feature that is controlled both by the background color and the air temperature.
The Pacific treefrog is a very adaptable species, which, despite its name, can often be found on the ground near ponds, springs, or streams. Tadpoles feed predominantly on plant material, while adults consume insects such as flies, gnats, and mosquitos, which they capture using their long, sticky tongues.
Due to the sensitivity of this species to environmental change, it is considered an indicator species and thus can be used to assess the health of an ecosystem. They are especially useful as an indicator species in urban environments, as even small changes can disrupt their breeding ecology.
