User:Xiaojianli2004/Mountain yellow-legged frog

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Description

Mountain yellow-legged frog

Rana muscosa is 4 to 8.9 centimeters long. Females tend to be larger than males. Its color and patterning are variable. It is yellowish, brownish, or olive with black and brown markings. The underside of its hind legs can be different hues of yellow, from an bold sun yellow to a lighter pale yellow; larger ones may can hints of orange on their hind legs. The throats of of it range from white to yellow. Along with its variable coloration, the frog also has a dorsal pattern with dark spots in different shapes and sizes. Its species name muscosa is from the Latin meaning "mossy" or "full of moss", inspired by its coloration. It may have light orange or yellow thighs. When handled, the frog emits a defensive odor reminiscent of garlic.

Habitat

The frog occurs in mountain creeks, lakes and lakeshores, streams, and pools, preferring sunny areas. It rarely strays far from water, and can remain underwater for a very long time, likely through cutaneous gas exchange. As such, adults can be found on rocks around shorelines. Close proximity to water is important because eggs are either laid underwater attached to rocks or in shallow waters. The tadpoles require a permanent water habitat for at least two years while they develop. This is because tadpoles can die from a lack of moisture, especially dry summers. The frog has been noted at elevations of between about 1,214 and 7,546 feet (370 and 2,300 meters) in Southern California. These habitats are primarily found in north of California in Sierra Nevada and south of California in the Transverse ranges.

Biology

Tadpole stage

The frog emerges from its wintering site soon after snowmelt. Its breeding season begins once the highest meltwater flow is over, around March through May in the southern part of its range, and up to July in higher mountains to the north. Fertilization is external, and the egg cluster is secured to vegetation in a current, or in still waters sometimes left floating free. How long it takes for breeding onset varies from 1-4 years depending on the levels of snow and temperature. Very cold temperatures may cause death of larvae. The juvenile may be a tadpole for 3 to 4 years before undergoing metamorphosis. However, this rate heavily varies depending on the temperature and elevation of the area. There are two classes of tadpoles: first year tadpoles and second year tadpoles. Metamorphosis tends to happen the second summer of tadpole life. They are called metamorphs when this transition from tadpole to young frog is occurring. They are then called a juvenile when it survives one winter. It becomes ready to reproduce after 2 years of the juvenile stage. It is found that the growth and development rate is slower at higher elevations.

The frog lacks a vocal sac. Its call is raspy, rising at the end. During the day, it calls underwater.

The frogs tend to be less active during the winters and more active during the mating season. For years when there is heavy snow at high elevations, they may only be active for 90 days in the summer. Hibernation tends to happen underwater or in the crevices of stream banks. This occurs during the cold months of winter. Hibernation ends in the spring to start the breeding season.

This species feeds on aquatic insects and benthic invertebrates. Their diet varies depending on the habitat type. When living in streams, it tends to eat terrestrial insects such as beetles, ants, bees, wasps, flies, and dragonflies. They are also known to eat larvae of other frogs and toads, as well as commit cannibalism.

Decline

Once a common species, Rana muscosa was absent from much of its native range by the 1970s. Over the course of the last hundred years, 90% of its populations have been eliminated. The frog was known from 166 locations in the Southern California mountains, and as of 2007, only seven or eight remained. The 2009 discovery of R. muscosa at two locations in the San Bernardino National Forest was newsworthy. The frog is represented in the Sierra Nevada by three or four populations. Its decline is attributed to many factors, including introduced species of fish such as trout, livestock grazing, chytrid fungus, and probably pesticides, drought, and ultraviolet radiation. Recreational activities in streams have also had an impact.

Introduced fish species

Trout were introduced to lakes and streams throughout the Sierra Nevada in the late 1800s to increase recreational fishing in the area. 90% of these Sierra Nevada lakes and streams did not previously have fish in them. The fish feed on tadpoles, a main prey item. The fish feed on tadpoles, a main prey item. Some of these fish types that prey on tadpoles include the brown, golden, and rainbow trout, as well as the brook char. The introduced trout have changed the distribution of several native species in the local ecosystems. Most of the mountain yellow-legged frog populations did not evolve to adapt to the trout. The trout caused populations to isolate, restricted the amount of available habitats, and increased the chances of extinction. After the removal of fish from several lakes, the frog reappeared and its populations increased. It then began to disperse to other suitable habitats nearby.

Conservation

In 2021, the Aquarium of the Pacific partnered with government organizations like the California Department of Fish and Wildlife to create a facility for taking care of mountain yellow-legged frogs. This was in response to recent wildfires which harmed their habitats. Following the wildfires, wildlife agencies found and moved these frogs into places like the facility established by the Aquarium of the Pacific. These efforts help the species recover from natural disasters and prevent extinction.