Foothill Yellow-legged Frog
Encyclopedia
The Foothill Yellow-legged Frog (Rana boylii) is a small-sized (3.72-8.2 cm) frog
from the Rana
genus in the Ranidae family. This species can be found from northern Oregon
, down California’s
west coast, and into Baja California
, Mexico
. Both the Columbia Spotted Frog
and the Cascades Frog
, also part of the Rana
genus, live in the northern regions of this frog's territory. They prefer to live in streams and rivers, and lay their eggs in masses attached to rocks underwater.
, or the back of the frog. It is commonly spotted or mottled
but occasionally is plainly colored. Adults have yellow coloration under the legs, which may extend to their abdomen, but this characteristic is faint or absent in young frogs. There is a triangular, buff-colored patch on the snout, and, unlike other frogs in the Rana
genus, there is no eye stripe. The throat and chest are often boldly mottled; moreover, the species has indistinct dorso-lateral skin folds and granular skin. Males of this species develop a nuptial pad
on their thumb base during the breeding season. These frogs can be identified by their rough skin, horizontal pupils, fully webbed hind feet, and its habit to jump into moving water. However, tadpoles of this species resemble that of their rival, the Western Toad or Bufo boreas. The R. boylii as tadpoles have fairly flattened tails that lack color at the end and are the tallest in the mid section. The mouth of the tadpoles are made for suction to rocks with lip, known as labial
, teeth rows used for scraping algae and diatoms, unicellular algae with cells walls that contain silica, off of the rocks they are clinging to. The mouth of the young R. boylii is also helpful in identifying it from B. boreas because the young Foothill Yellow-Legged frogs develop more defined teeth rows after three weeks while their counterparts do not.
” and that “these food effects may be mediated through diet induced changes in thyroid
function,” which means that the food that the tadpoles ingest dictates the changes in the thyroid gland's production of certain proteins. Tadpoles most commonly feed on algae, diatom
s, and detritus
. As the species grows older, it changes its diet to animal tissue which must be swallowed whole because the frog's jaw is structured on a hinge joint that does not allow for sideways movement as in humans. Adult frogs eat a range of foods such as moths, ants, grasshoppers, hornets, beetles, flies, water striders, and snails.
substrates. Thus, R. boylii avoids rapid waters to protect the egg masses from being swept away. This technique is why the species has a wide window for breeding season. If the conditions are not perfect to their standards, they will refuse to mate and will wait until the water velocities go back down to ideal.
For the Foothill Yellow-Legged Frog, the oviposition, or the depositing of eggs, is somewhat sporadic because delays such as rains could cause problems like unwanted removal of eggs. The males also perform mating calls mostly underwater, and those above the water are faint and hard to hear over fifty meters. After the frogs have successfully mated, the egg masses are ovipositioned about half a meter down in the river and with flow velocities ranging from 0.1 to 0.6 m3/second. These egg masses can be anywhere from 100 to 1000 eggs in one batch. They are contained in a bluish gel that disappears once the eggs take on water, and the dark ovum
, center of egg, is covered by three jelly envelopes that are about 5.4 mm in diameter. Eggs hatch in about five to over thirty days depending on the temperature that the mass is at and the surrounding water. The tadpoles continue to stay associated with the egg mass for several days, and continue to need higher temperatures to grow quickly. By the time the tadpoles reach about forty millimeters, roughly 1 and a half inches, they are adults and their reproductive organs are mostly functional. The frogs are usually fully developed by the summer after their first metamorphosis
, though some begin breeding after six months.
, down California's
coast where it most commonly found, and into Baja California
, Mexico
. They prefer to be in streams and rivers versus still ponds and perfer flowing water that has either rocky substrate or sunny banks and rivers and streams that contain shallow areas that still have water flow.
. The frog secretes a peptide
through the skin and the hydrophobic (water repellent) sections of the peptide access to fungi
that want to attach to the amphibian. This ability can also be found in other Rana
species including the Cascades Frog
and the Moor Frog
. The former secretes a milky substance that fights against fungal infections and the latter uses its capability to have males turn blue during mating season. Still, the Foothill Yellow-Legged Frog's chemical defense has not been fully examined and is in the process of being understood. Although not much is known about it, this ability of the species has been of interest to many anti-fungal cream companies because of its overall effectiveness. However, current pesticide use has caused problems for the frog. So far, it has been concluded that though exposure to carbaryl
, a substance found in common pesticides, does not kill the frogs, it does lower the peptides’ abilities to defend the species against invaders like the chytrid, B. dendrobatidis. More research is being done to see the full effects that pesticides may have on R. boylii.
, California
there is a dam on the major river of the frog's home which has affected about 94% of the possible procreation areas for the frogs, which has endangered the population. One study suggests that the “data from a comparably-sized undammed river fork in the same system…demonstrated that both the number of potential sites and the total number of egg masses were…higher on this fork than in our main stem,” and so the unseasonal flooding required by the dam was negatively affecting the mating behavior of the frog. The temperature of the water in Trinity County
is also lower than it was before the dam was put into place. To keep up with demands of fisheries, the water’s temperature is kept artificially lower than normal, which consequently slows the development of R. boylii. Therefore, the colder temperatures are making it more difficult for the frogs to grow quickly, which sometimes leaves the species prey to many other animals that dine on their young. The problems occurring between the Foothill Yellow-Legged Frog and the dam are being handled by several herpetological organizations, along with the Forest Service, to find ways to alter the effects in a beneficial way for the frog.
This species is also estimated to be gone from most of its range in the Sierra Nevada mountains, espcially south of highway 80 where pesticides often contaminate rivers and dams block the essential stream flows.
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
from the Rana
Rana (genus)
Rana is a genus of frogs. Species include such archetypal pond frogs as the common frog of Europe, brown frogs, and the New and Old World true frogs, including the various species of leopard frogs and the American bullfrog. Members of this genus are found through much of Eurasia, North America,...
genus in the Ranidae family. This species can be found from northern Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, down California’s
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
west coast, and into Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Both the Columbia Spotted Frog
Columbia Spotted Frog
The Columbia Spotted Frog, Rana luteiventris, is a North American species of frog. It is green to brown in color with spots on the dorsal surface. The belly and upper lip are white in color. Individuals can be distinguished from other Rana species by their shorter back legs, narrow snout and...
and the Cascades Frog
Cascades Frog
The Cascades Frog is a species of frog in the Ranidae family.It is found in western United States and possibly Canada, mainly in the Cascade Range and Olympic Mountains.-Description:-Appearance:...
, also part of the Rana
Rana (genus)
Rana is a genus of frogs. Species include such archetypal pond frogs as the common frog of Europe, brown frogs, and the New and Old World true frogs, including the various species of leopard frogs and the American bullfrog. Members of this genus are found through much of Eurasia, North America,...
genus, live in the northern regions of this frog's territory. They prefer to live in streams and rivers, and lay their eggs in masses attached to rocks underwater.
Appearance
The Foothill Yellow-legged Frog has a grey, brown, or reddish dorsumDorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
, or the back of the frog. It is commonly spotted or mottled
Mottle
Mottle or mottling is the appearance of uneven spots. It is commonly used to describe plants or the skin of animals. In plants, mottling usually consists of yellowish spots on plants, and is usually a sign of disease or malnutrition...
but occasionally is plainly colored. Adults have yellow coloration under the legs, which may extend to their abdomen, but this characteristic is faint or absent in young frogs. There is a triangular, buff-colored patch on the snout, and, unlike other frogs in the Rana
Rana (genus)
Rana is a genus of frogs. Species include such archetypal pond frogs as the common frog of Europe, brown frogs, and the New and Old World true frogs, including the various species of leopard frogs and the American bullfrog. Members of this genus are found through much of Eurasia, North America,...
genus, there is no eye stripe. The throat and chest are often boldly mottled; moreover, the species has indistinct dorso-lateral skin folds and granular skin. Males of this species develop a nuptial pad
Nuptial pad
A nuptial pad is a secondary sex characteristic present on some mature male frogs and salamanders. Triggered by androgen hormones, this breeding gland appears as a spiked epithelial swelling on the forearm and prepollex that aids with grip, used primarily by males to grasp females during amplexus...
on their thumb base during the breeding season. These frogs can be identified by their rough skin, horizontal pupils, fully webbed hind feet, and its habit to jump into moving water. However, tadpoles of this species resemble that of their rival, the Western Toad or Bufo boreas. The R. boylii as tadpoles have fairly flattened tails that lack color at the end and are the tallest in the mid section. The mouth of the tadpoles are made for suction to rocks with lip, known as labial
Labial
Labial may refer to:*the lips*the labia *In linguistics, a labial consonant*In zoology, the labial scales...
, teeth rows used for scraping algae and diatoms, unicellular algae with cells walls that contain silica, off of the rocks they are clinging to. The mouth of the young R. boylii is also helpful in identifying it from B. boreas because the young Foothill Yellow-Legged frogs develop more defined teeth rows after three weeks while their counterparts do not.
Food sources
Food supplies such as algae that the tadpoles eat also affects the sexual maturity of the species. It has been reported that the “amount of protein in different algae, can affect size at and time to metamorphosisMetamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
” and that “these food effects may be mediated through diet induced changes in thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...
function,” which means that the food that the tadpoles ingest dictates the changes in the thyroid gland's production of certain proteins. Tadpoles most commonly feed on algae, diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s, and detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
. As the species grows older, it changes its diet to animal tissue which must be swallowed whole because the frog's jaw is structured on a hinge joint that does not allow for sideways movement as in humans. Adult frogs eat a range of foods such as moths, ants, grasshoppers, hornets, beetles, flies, water striders, and snails.
Mating habits
The mating “ceremonies” begin in spring where adult frogs congregate on sandy and/or rocky bars to mate. It was previously believed that they did so from March to May, but recent experiments have determined that time to be closer to April to late June. High stream velocities, however, may dislodge R. boylii egg masses from ovipositionOviposition
Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....
substrates. Thus, R. boylii avoids rapid waters to protect the egg masses from being swept away. This technique is why the species has a wide window for breeding season. If the conditions are not perfect to their standards, they will refuse to mate and will wait until the water velocities go back down to ideal.
For the Foothill Yellow-Legged Frog, the oviposition, or the depositing of eggs, is somewhat sporadic because delays such as rains could cause problems like unwanted removal of eggs. The males also perform mating calls mostly underwater, and those above the water are faint and hard to hear over fifty meters. After the frogs have successfully mated, the egg masses are ovipositioned about half a meter down in the river and with flow velocities ranging from 0.1 to 0.6 m3/second. These egg masses can be anywhere from 100 to 1000 eggs in one batch. They are contained in a bluish gel that disappears once the eggs take on water, and the dark ovum
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
, center of egg, is covered by three jelly envelopes that are about 5.4 mm in diameter. Eggs hatch in about five to over thirty days depending on the temperature that the mass is at and the surrounding water. The tadpoles continue to stay associated with the egg mass for several days, and continue to need higher temperatures to grow quickly. By the time the tadpoles reach about forty millimeters, roughly 1 and a half inches, they are adults and their reproductive organs are mostly functional. The frogs are usually fully developed by the summer after their first metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
, though some begin breeding after six months.
Habitat
The Foothill Yellow-Legged Frog has a territory that spans from northern OregonOregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, down California's
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
coast where it most commonly found, and into Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. They prefer to be in streams and rivers versus still ponds and perfer flowing water that has either rocky substrate or sunny banks and rivers and streams that contain shallow areas that still have water flow.
Chemical defense
R. boylii has a chemical defense in which it can protect itself from fungal infections, such as the Batrachochytrium dendrobatidisBatrachochytrium dendrobatidis
Batrachochytrium dendrobatidis is a chytrid fungus that causes the disease chytridiomycosis. In the decade after it was first discovered in amphibians in 1998, the disease devastated amphibian populations around the world, in a global decline towards multiple extinctions, part of the Holocene...
. The frog secretes a peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
through the skin and the hydrophobic (water repellent) sections of the peptide access to fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
that want to attach to the amphibian. This ability can also be found in other Rana
Rana (genus)
Rana is a genus of frogs. Species include such archetypal pond frogs as the common frog of Europe, brown frogs, and the New and Old World true frogs, including the various species of leopard frogs and the American bullfrog. Members of this genus are found through much of Eurasia, North America,...
species including the Cascades Frog
Cascades Frog
The Cascades Frog is a species of frog in the Ranidae family.It is found in western United States and possibly Canada, mainly in the Cascade Range and Olympic Mountains.-Description:-Appearance:...
and the Moor Frog
Moor Frog
The Moor Frog is a slim, reddish-brown, semi-aquatic amphibian native to Europe and Asia. It is a member of the family Ranidae, or "true frogs".-Taxonomy:...
. The former secretes a milky substance that fights against fungal infections and the latter uses its capability to have males turn blue during mating season. Still, the Foothill Yellow-Legged Frog's chemical defense has not been fully examined and is in the process of being understood. Although not much is known about it, this ability of the species has been of interest to many anti-fungal cream companies because of its overall effectiveness. However, current pesticide use has caused problems for the frog. So far, it has been concluded that though exposure to carbaryl
Carbaryl
Carbaryl is a chemical in the carbamate family used chiefly as an insecticide. It is a white crystalline solid commonly sold under the brand name Sevin, a trademark of the Bayer Company. Union Carbide discovered carbaryl and introduced it commercially in 1958...
, a substance found in common pesticides, does not kill the frogs, it does lower the peptides’ abilities to defend the species against invaders like the chytrid, B. dendrobatidis. More research is being done to see the full effects that pesticides may have on R. boylii.
Environmental issues
Along with the problems associated with pesticides being washed up in the Foothill Yellow-Legged Frog's habitat, in Trinity CountyTrinity County, California
Trinity County is a large, rugged and mountainous, heavily forested county located in the northwestern portion of the U.S. state of California, along the Trinity River and within the Salmon/Klamath Mountains. It covers an area of over two million acres , and as of the 2010 census its population...
, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
there is a dam on the major river of the frog's home which has affected about 94% of the possible procreation areas for the frogs, which has endangered the population. One study suggests that the “data from a comparably-sized undammed river fork in the same system…demonstrated that both the number of potential sites and the total number of egg masses were…higher on this fork than in our main stem,” and so the unseasonal flooding required by the dam was negatively affecting the mating behavior of the frog. The temperature of the water in Trinity County
Trinity County, California
Trinity County is a large, rugged and mountainous, heavily forested county located in the northwestern portion of the U.S. state of California, along the Trinity River and within the Salmon/Klamath Mountains. It covers an area of over two million acres , and as of the 2010 census its population...
is also lower than it was before the dam was put into place. To keep up with demands of fisheries, the water’s temperature is kept artificially lower than normal, which consequently slows the development of R. boylii. Therefore, the colder temperatures are making it more difficult for the frogs to grow quickly, which sometimes leaves the species prey to many other animals that dine on their young. The problems occurring between the Foothill Yellow-Legged Frog and the dam are being handled by several herpetological organizations, along with the Forest Service, to find ways to alter the effects in a beneficial way for the frog.
This species is also estimated to be gone from most of its range in the Sierra Nevada mountains, espcially south of highway 80 where pesticides often contaminate rivers and dams block the essential stream flows.