Frog of the Week

Foothill Yellow-Legged Frog (Rana boylii)

photo by William Flaxington

Common Name: Foothill Yellow-Legged Frog
Scientific Name: Rana boylii
Family: Ranidae – True Frog family
Locations: United States
US Locations: California and Oregon
Size: 1.5 – 3.2 inches ( 3.8 – 8.1 cm)

The Foothill Yellow-Legged Frog is known for the yellow markings on the underside of their legs and extends to their belly. They live along the streams in the mountains of California and Oregon.

The breeding season starts at the end of March and continues to the end of May. Mating takes place in streams and rivers instead of the usual ponds and lakes that other frogs use. The males will call underwater to try to attract females. They do occasionally call above the water. Once the female selects a male, the male will grasp her from behind in the amplexus position. The female will lay between 300 – 2000 eggs, averaging around 900, and the male will then fertilize them.

Neither parent provides any parental care. The eggs hatch between 5 – 37 days days and the tadpoles transform between 3 and 4 months.Breeding end of March to start of May, streams rivers, males call underwater, 300 – 2,000, averaging 900. transform 3-4 months, hatch 5 – 37 days, typical breeding

The Foothill Yellow-Legged Frog is a candidate for the United States’ Endangered Species List and is already listed on the state of California’s Endangered Species List. The International Union for the Conservation of Nature (IUCN) Red List also lists them as Near Threatened. The frogs have disappeared from almost 45% of its range. Numerous different things have affected the frog’s populations. The large, introduced American Bullfrogs (Rana catesbeiana) feast upon any smaller frog than it, including the Foothill Yellow-Legged Frog. Introduced trout Pesticide use has decreased population numbers. Dams have altered the habitat that they call home.

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California Tree Frog (Pseudacris cadaverina)

photo by Chris Brown / USGS

Common Name: California Tree Frog or California Chorus Frog
Scientific Name: Pseudacris cadaverina or Hyliola cadaverina
Family: Hylidae – Tree Frog family
Locations: Mexico and the United States (California)
Male Size: 1.4 inches (36 mm)
Female Size: 1.8 inches (45 mm)

The California Tree Frog can be called the California Chorus Frog due to them being placed in the Chorus Frog genus – Pseudacris. Researchers have proposed moving the frog into the genus Hyliola along with the Pacific Chorus Frog. They are more similar to other Chorus Frogs, in that they aren’t found high in the trees. These frogs like to live in crevices or cavities in boulders along streams. The frogs blend into these boulders with their rough skin and gray / brown color.

Breeding takes place in the streams from February to October. Reproduction for the California Tree Frog is pretty standard. Males will call from the streams to attract potential mates. Once the female selects the mate, the male will grasp her from behind in amplexus. The female then lay her eggs and the male then fertilizes them. Neither parent provide any care for their offspring. The larval period for the tadpoles ranges from 40 – 75 days.

Frog of the Week

Southern Mountain Yellow-Legged Frog (Rana muscosa)

Rana_muscosa.jpg
photo by Chris Brown (USGS)
Conservation status is Endangered


Common Name: Southern Mountain Yellow-Legged Frog
Scientific Name: Rana muscosa
Family: Ranidae – True Frog family
Locations: United States – California
Size: 2 – 3 inches (5 – 7.6 cm)

The Southern Mountain Yellow-Legged Frog is a federally listed endangered species by the United States. They live in only few small areas in southeastern California near the Sierra Nevada Mountains. It was not always like this. They used to be a common species before they started to disappear.

There are many reasons for the declines. Trout was introduced into the Sierra Nevada Mountains to increase recreational fishing there. These non-native trouts eat on the tadpoles of the frog as they are predators. Studies shown that removing trouts from lakes in the Southern Mountain Yellow-Legged Frog’s habitat allows the frog repopulate the area and increase numbers.

photo by William Flaxington

Another key reason for the population decline of the Southern Mountain Yellow-Legged Frog is the introduction of Chytrid Fungus into their environment. Chytrid Fungus is a deadly pathogen that thickens the skin of the frog. The thicker skin prevents the ability of the frog to breathe and drink through its skin and eventually causes death. The disease has lead to widespread deaths of amphibians all over the world. Sadly, it has also affected the Mountain Yellow-Legged Frog. Those are the two main reasons for the decline but other reasons include pesticides, climate change, habitat degradation and fragmentation, and drought.

Luckily, zoos are trying to help the species. The San Diego Zoo has been captive breeding the Southern Mountain Yellow-legged Frog and releasing the tadpoles into the wild. The Oakland Zoo and the San Francisco Zoo have been catching juvenile frogs and raising them in captivity. They give the frogs anti-fungal baths and when they are older, they release them.