Pseudacris triseriataWestern Chorus Frog

Geographic Range

The western chorus frog is found in the middle to eastern portions of the North American continent. Its range extends from southern Quebec and northern New York west to South Dakota, then south to Kansas and Oklahoma (Harding 1997).

Habitat

Western chorus frogs can be found in a variety of habitats, including marshes, meadows, swales, and other open areas. Less frequently they can be found in fallowed agricultural fields, damp woods, and wooded swamps. These areas of less permanent water offer reduced risk of egg and tadpole predation by other animals such as fish. There is a trade-off, however, as these temporary bodies of water can dry up in years of drought, resulting in reproductive failure for that year (Harding 1997).

Physical Description

The western chorus frog is characterized by a white or cream colored stripe along the upper lip, bordered by a dark brown stripe running through the eye from the nostril to the groin. There are usually 3 dark stripes running down the back, although these may be broken into rows of spots in some specimens. Background color ranges from brown to gray or olive. The underside is white or cream colored, possibly with dark spots on the chin and throat (Conant and Collins, 1991). Males have a yellow colored vocal sac that appears as a dark, loose flap of skin when not calling. The skin of the western chorus frog is typically moist and bumpy, and the toes end in slightly expanded toepads. Adult length is typically 1.9 to 3.9 cm (.75" to 1.5"), with males usually smaller than females. P. triseriata tadpoles have gray or brown bodies round in shape. Their tail fins are clear, often with dark flecks. The intestinal coil can be seen through the bronze belly skin. Maximum length before metamorphosis is about 3cm (1.2 inches)(Harding 1997).

  • Sexual Dimorphism
  • female larger
  • Range length
    19.0 to 39.0 mm
    0.75 to 1.54 in

Development

The rate of development of the eggs and larvae is dependent on water temperature, with specimens in colder water requiring more time for development. Maximum length before metamorphosis is about 3cm.

Reproduction

In Michigan, the breeding season of Pseudacris triseriata begins in mid-March and runs through late May, although most activity occurs in April. These periods can vary, with breeding taking place earlier in the southern end of its range and later in the northern end. (Conant and Collins, 1991). Breeding sites include the edges of shallow ponds, flooded swales, ditches, wooded swamps, and flooded fields. Breeding choruses early in the season can be heard on clear, sunny days, but shift to evenings or cloudy, rainy days as the season progresses. Picking the small end of a high quality fine tooth comb with a fingernail can reproduce the call of the western chorus frog. The call sounds like "Cree-ee-ee-ee-eek", rising in speed and pitch as it progresses.

During amplexus, the female will lay 500-1500 eggs in several loose, gelatinous clusters attached to submerged grasses or sticks. Each cluster will typically have 20 to 300 eggs. Hatching generally occurs in 3 to 14 days and tadpoles transform into tiny froglets 40 to 90 days thereafter. The rate of development of the eggs and larvae is dependent on water temperature, with specimens in colder water requiring more time for development. Western chorus frogs can mature and breed in less than one year (Harding 1997).

  • Breeding interval
    Striped Chorus Frogs breed each year in the spring.
  • Breeding season
    Breeding occurs from March to May.
  • Range number of offspring
    500.0 to 1500.0
  • Range time to hatching
    14.0 (high) days
  • Range
    40.0 to 90.0 days

After laying their eggs in clusters on vegetation there is no further parental care in Striped Chorus Frogs.

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Most Striped Chorus Frogs will probably die as tadpoles or froglets. Once they reach adulthood, Striped Chorus Frogs may live for about 5 years.

  • Average lifespan
    Status: wild
    5.0 years

Behavior

Western chorus frogs tend to remain close to their breeding grounds throughout the year. They often hide from predators beneath logs, rocks, leaf litter, and in loose soil or animal burrows. They will typically hibernate in these places as well (Harding 1997).

Communication and Perception

Picking the small end of a high quality fine tooth comb with a fingernail can reproduce the call of the western chorus frog. The call sounds like "Cree-ee-ee-ee-eek", rising in speed and pitch as it progresses. Striped Chorus Frog males use these calls to attract females to breeding sites during the breeding season. Striped Chorus Frogs also use their keen vision to capture prey.

Food Habits

Western chorus frogs eat a variety of small invertebrates, including ants, flies, beetles, moths, caterpillars, leaf hoppers, and spiders. Newly formed froglets feed on smaller prey, including mites, midges, and springtails. Tadpoles are herbivorous, foraging mostly on algae (Harding 1997).

  • Primary Diet
  • carnivore
    • eats non-insect arthropods

Predation

Striped chorus frogs are preyed on by large birds, small mammals, and snakes. Tadpoles and froglets can be preyed on by other frogs, crayfish, fish, turtles, and dragonfly larvae.

Ecosystem Roles

Striped Chorus Frogs help to control insect populations where they live, they also act as an important food source for their predators.

Economic Importance for Humans: Positive

The western chorus frog (and most other frogs) acts as a critical indicator species. Because the larval and adult forms of this species occupy different levels of the food chain, anomalies (such as deformities) or a reduction in reproductive success can be linked to either aquatic or terrestrial ecosystems, depending on the life stage of the animal. This makes this species valuable in determining the overall health of both ecosystems. The permeable skin of the western chorus frog also makes it susceptible to contaminants and other external stimuli. Changes in morphology or ecology of this species might indicate high levels of pollution or other activity detrimental to their well being.

Conservation Status

The western chorus frog can be common to locally abundant, although some areas have shown a decline. The subspecies Pseudacris triseriata maculata is listed as special concern in the state of Michigan. This species appears to be quite tolerant of human activities, considering its presence in agricultural and suburban areas. Caution must be exercised during agricultural practices, as runoff containing pesticides, herbicides, and fertilizers often fills breeding ponds, making eggs and larvae susceptible to detrimental effects (Harding 1997).

Contributors

Kevin Gardiner (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

crepuscular

active at dawn and dusk

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

References

Conant, R., J. Collins. 1991. Peterson Field Guides: Reptiles and Amphibians of Eastern and Central North America. New York: Houghton Mifflin Company.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, MI: The University of Michigan Press.