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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