Western Chorus Frog

Western Chorus Frog
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Amphibia
Order:	Anura
Family:	Hylidae
Genus:	Pseudacris
Species:	P. triseriata
Binomial name
Pseudacris triseriata Wied-Neuwied, 1838
Subspecies
P. t. triseriata – Striped, Midland, or Western Chorus Frog P. t. kalmi – New Jersey Chorus Frog
Synonyms
Hyla triseriata Helocaetes triseriatus Chorophilus triseriatus Chorophilus nigritus triseriatus

The Western Chorus Frog, Striped Chorus Frog^[1], or Midland Chorus Frog^[2] (Pseudacris triseriata) is a species of tree frog found in Canada and the United States.

Description and Identification

Western chorus frogs are small (1.5 inch or about 40 mm), smooth skinned, greenish-grey, reddish, olive or brown colored frogs. These differences in color can occur locally and should not be confused for range specific populations. Typically, these frogs contain three dark brown or grey stripes which extend down the entire dorsal side. The dorsal stripes can be broken up, reduced or even absent in certain specimens. The white or cream colored underside or ventral side of the frog typically has dark scattered flecks. A single white stripe runs along the upper lip and a heavy dark stripe runs through the eye and along each side from snout to leg. A dark triangular shaped spot on the head may also be seen in some individuals. These frogs have small round toes without pads and very little webbing between each toe.

Typically, males are smaller than females and can be told apart from the females by the yellow vocal sac when calling. When not calling, this sac looks like a dark loose flap of skin beneath the throat.

Tadpoles of the western chorus frog have gray or brown bodies. The body shape of the tadpoles is round with clear tail fins and dark flecks. It is said the intestinal coil can be seen through the belly skin if you are looking closely.

Taxonomy

P. triseriata was once considered a subspecies of the Southern Chorus Frog, P. nigrita, but was reclassified as its own species with four subspecies: P. t. triseriata,^[2] P. t. kalmi, P. t. maculata,^[1] and P. t. feriarum. The latter two have since been granted an independent species status.

Distribution

The chorus frog has a huge home range. Western chorus frogs live from Canada to the Gulf of Mexico, and New Jersey to central Arizona. The frogs lives from near sea-level to about 12,000 ft (3,700 m) above sea-level and are capable of surviving temperatures as low as –8°C.^[3]

Habitat

Western chorus frogs live in a variety of different habitats, but areas of less permanent water increases the risk of predation on eggs and/or tadpoles. In order to compensate for this, chorus frogs stick to mostly permanent freshwater areas, such as marshes, river swamps, meadows, grassy pools and other open areas found in mountains and prairies. The western chorus frog remains close to these permanent aquatic habitats, since they provide excellent mating, breeding and hibernation grounds. Since these areas tend to dry out, these frogs can be, but are less commonly found in fallowed agricultural fields, damp woodlands, roadside ditches and wooded swamps.

Behavior

Due to their nocturnal and secretive nature, these frogs are rarely seen. The best time to see western chorus frogs is on warm nights when they come out to call. Both males and females call in large choruses. Males use a special call to attract several potential mates to breeding sites. The western chorus frog call can be heard from half a mile away. The call is a very distinct “cree-ee-ee—eeek”, but can be confused with the upland chorus frog. Calling can occur for ½–2 seconds and can occur 18–20 times in a minute. The higher the temperature the more frequent calls occur in a minute, (30–90 calls per minute). One can imitate the “cree-ee-eek” call of the western chorus frog by stroking the edge of a pocket comb. The western chorus frog relies heavily on secrecy to keep themselves safe from predators. Any disturbances to the frogs environment, causes them to stop calling and dive into the depths of whatever water source they reside near, under leaf litter, logs, rocks, or loose soil. These terrestrial hiding spots serve, not only as hiding places, but as hibernation places for the frogs during the winter.

Diet

Western chorus frogs not only come out at night to chorus, but also to feed. The diet of an adult consists of small invertebrates and arthropods, like flies, mosquitos, ants, small beetles, moths and caterpillars, grasshoppers and spiders. Froglets (the transition or metamorphic phase between tadpole and frog) will feed on smaller prey like mites, midge and springtails. Tadpoles are strictly herbivorous and forage on algae.

Reproduction

Breeding occurs at different times throughout the various states this frog resides in. Typically, western chorus frog’s breeding season starts in March through May with April being the most active month. However, breeding takes place earlier in southern parts and can vary through the frogs entire range. The earliest sign of western chorus frog breeding occurs with choruses heard on sunny days. Males call to potential females over the course of several days to months. As the season continues, these competing male choruses move to the evenings and cloudy rainy days. The life span of these frogs averages to five years. After the mating has occurred, females can lay between 500-1500 eggs during the entire breeding season. The female lays one cluster at a time, which can contain 20-300 eggs. The eggs are retained in a loose gelatinous cluster, submerged below the water and stuck to weeds or grasses. The grasses and weeds are found along the edges of shallow ponds, flooded swales, roadside ditches, flooded fields, open areas and swamps. The eggs will hatch into tadpoles between 3–14 days of being laid. However, water temperature can be a limiting factor in the growth of both eggs and tadpoles. Colder water temperatures prevent the tadpoles and eggs from growing. Tadpoles metamorphose into froglets 40–90 days afterwards.

Conservation Concern and Ecological Role

Although quite adaptable and tolerant to human activity, western chorus populations are declining in certain areas. Labeled as in least concern on the IUCN list, the US Federal List has the species labeled as no special status. The western chorus frog plays an important role as an indicator species. If deformities, reduction in reproductive success or changes in morphology occur in either the larval or adult forms, it could indicate pollution or toxic substance in the environment. Therefore, the health of these frogs could be valuable in determining the health of ecosystems and if an agricultural practices have leaked any pesticides, herbicides or fertilizers into the environment. In addition, these frogs are excellent in controlling insect populations, thus further benefiting humans and the environment.

References

1. ^ ^{a b} Boreal Chorus Frog, Natural Resources Canada
2. ^ ^{a b} Midland Chorus Frog, Natural Resources Canada
3. ^ Adaptations of Frogs to Survive Freezing

• Hammerson (2004). Pseudacris triseriata. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006. Database entry includes a range map and justification for why this species is of least concern.
• IUCN RangeMap: Pseudacris triseriata
• Animal Diversity Web: Pseudacris triseriata
• Illinois Natural History Survey: Pseudacris triseriata
• Amphibian Species of the World: Pseudacris triseriata
• Peterson Field Guide – Western Reptiles and Amphibians – 3rd Edition.
• Pough, F.H. Herpetology – Third Edition. Upper Saddle River, NJ: Pearson Education, 2004. Print.
• Environmental Education of Kids: Western Chorus Frog
• Western Chorus Frog
• Frogs Field ID’s - University of Wisconsin Sea Grant: The Western Chorus Frog
• eNature.com: Western Chorus Frog Pseudacris triseriata

External links

• Audio recording of Western Chorus Frog