Pseudacris comes from the Greek words pseudos, meaning “lie,” and akris, meaning “locust.” The species epithet triseriata refers to the three distinct stripes on the dorsum, as tri is Latin for “three” and seriata means “lines” or “serrations” in Latin (INHS Herpetology Collection).

hear call (5656.6K WAV file)

[call details here]

Description
Pseudacris triseriata is one of the smallest hylid frogs in North America with a snout-vent length ranging from 19 to 39 mm, but often around 38.1 mm and with females larger than males (Platz 1989, Powell et al. 1998, Wied-Neuwied 1834, Trauth et al. 2004). The head is longer than it is wide, with a pointed upper jaw that hangs over the lower jaw. The tympanum is circular and is about half of the eye diameter. The palms have numerous round tubercles and two small plantar tubercles (Hurter 1911). Finger III and toe III are the longest, while the other digits are much shorter. Webbing is barely present between all toes, and it reaches less than halfway up the toes (Hurter 1911, Wied-Neuwied 1834, Smith 1882). The dorsum is finely granulated, except for the dorsal surfaces of the head, limbs, and throat in males, which are smooth. The venter is coarse (Hurter 1911). The granulation is especially evident on the palms of the hands (Cope 1889).

DIAGNOSIS: (How this species is differentiated from similar species)

Pseudacris triseriata is morphologically similar to P. brachyphona, P. clarkii, P. crucifer, P. feriarum, P. kalmi, and P. maculata, which were all previously recognized as P. triseriata subspecies (see Comments). Pseudacris brachyphona only has two dorsal stripes that may curve inward like an X, whereas P. triseriata has three straight lines. Pseudacris clarkii has brighter green spots or stripes instead of the darker-colored stripes in P. triseriata. Unlike P. triseriata, P. crucifer has a dark X-shaped marking on the back and lacks the line on the upper lip (Powell et al. 1998). Compared to P. feriarum, P. triseriata often is more strongly-striped and P. feriarum has weaker markings. In more strongly-striped P. feriarum individuals, the stripes are usually thinner and more broken, except for at the eye where the stripe is strong (Powell et al. 1998). Pseudacris triseriata also has shorter hind legs and is generally longer and thinner than P. feriarum. Additionally, the snout in P. triseriata is more pointy, and the upper jaw in P. feriarum protrudes more than that of P. triseriata (Cope 1889). Pseudacris kalmi does not have an extensive range like P. triseriata, occurring only in parts of Delaware, Maryland, southern New Jersey, New York, and eastern Pennsylvania (Platz 1989). Pseudacris kalmi also has extremely short calls compared to P. triseriata (Platz and Forester 1988). Pseudacris maculata occurs from northwestern Ontario eastward to Winnipeg, Manitoba. This range extends to parts of Nebraska, South Dakota, Minnesota, Wisconsin, and New Mexico in the south. On the other hand, P. triseriata occurs south of this range, in most of Nebraska, eastern south Dakota, central Minnesota, northern Wisconsin, and Michigan (Platz 1989). Pseudacris maculata has three longitudinal rows of spots and shorter legs compared to P. triseriata, which has defined dorsal stripes and longer legs. Pseudacris triseriata also always has a light line along the upper lip (Platz 1989, Cope 1889). Pseudacris triseriata and P. maculata are typically distinguished by their ratio of tibia to snout-vent length, with P. triseriata having a larger tibia that is 42.6% the snout-vent length, and P. maculata having a smaller tibia that is 39.3% the snout-vent length (Rogic et al. 2015). Call analyses of P. maculata and P. triseriata from South Dakota to Oklahoma indicate that the two can have distinct calls. The northern call by P. maculata has a longer duration and lower pulse rate compared to the southern call by P. triseriata (Platz and Forester 1988, Platz 1989).

COLORATION: (In life and/or in preservative)

In life, the dorsum of P. triseriata ranges from brown to greenish-gray and has three longitudinal stripes that are darker gray or brown-black. The ventral surfaces are whitish and may have darker spots on the throat or chest. A dark triangle may appear between the eyes. The central stripe begins at the tip of the nose and runs as an unbroken line to the back, where the line is broken up into spots. The iris is gold. A black-brown stripe extends from the nose to the hind thighs. The hind legs are marbled with a pair of pale, dark bands that are barely lighter than the venter. The belly is white. The throat and chin are a brown-olive color, with males’ throats appearing darker during the breeding season. The ventral surface of the hind legs are reddish-gray (Hurter 1911, Powell et al. 1998, Wied-Neuwied 1834, Trauth et al. 2004).

VARIATION: (if known)

While the wild type coloration of P. triseriata consists of a brown dorsum with darker spots or stripes, the mutant phenotypes can be a brown, red, green, or red and green dorsum with either green or brown spots (Matthews and Pettus 1966).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Canada, United States

U.S. state distribution from AmphibiaWeb's database: Iowa, Illinois, Indiana, Kentucky, Michigan, New York, Ohio, Tennessee

Canadian province distribution from AmphibiaWeb's database: Newfoundland and Labrador, Ontario, Quebec

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (64 records).

The species has a wide range extending from extreme southern Ontario, Canada through the lower peninsula of Michigan, then into western New York through western Pennsylvania, Ohio, and Indiana to southern Illinois, western Kentucky, and northwest Tennessee (IUCN 2022, Moriarty Lemmon et al. 2007). The type locality is Mt. Vernon, Ohio River, Posey County, Indiana (Frost 2024). The species inhabits meadows, marshes, forest edges, and temporary ponds, usually in open country (IUCN 2022).

Life History, Abundance, Activity, and Special Behaviors
Individuals live up to six years and typically do not move more than 750 m from the hatching site in their lives (Platz and Forester 1988). Individuals reach reproductive maturity within one year, typically at the end of summer, and generally only breed once. Survival rates are low at each life stage (Whiting 2004).

Pseudacris triseriata spends winters underground or beneath surface cover. Breeding sites are generally temporary water sites that are shallow with low vegetation, such as flooded meadows and ditches (IUCN 2022). Breeding occurs in late February or early March and ends by late April. Females lay from 500 - 1500 eggs total in clusters of 20 - 100 (Trauth et al. 2004). In Quebec, breeding occurs after snow melts, in early April through May, and tadpoles emerge in late June (Whiting 2004).

Early in the breeding season, P. triseriata likely depend on glycogen and triglyceride in stored energy reserves, as prey are not present until later in the season and digestion is difficult in cold temperatures. In males, energy use is mainly dedicated to calling behaviors, while the energy costs of gametogenesis are less. In females, energy is mainly spent on gametogenesis. Due to this difference in energy use, males have higher somatic lipid contents than females in the early breeding season. Glycogen levels in the liver and bodies of males are also greater, possibly explaining sexual dimorphism in liver size, where males have larger livers than females (Duffitt and Finkler 2011).

For males and females, the relationship between stored energy content and body size differs. Lipid and glycogen increases in males correlate with increased body size, but not in females. Increased body size in males also correlates with reproductive success due to various factors, including acoustic qualities for calls, call intensity, better outcomes in direct competition with other males. Therefore, stored energy content is higher in larger males because larger males require more lipid and glycogen reserves for calling activity (Duffitt and Finkler 2011).

Advertisement calls in P. triseriata consist of one note. Courtship calls, which are modifications of the advertisement call, contain multiple notes with higher pulse rates, lower dominant frequencies, and faster calling rates. Males switch from advertisement calls to courtship calls when approached by conspecifics, but will switch back when the other frog becomes motionless or leaves. Males often do not move when producing courtship calls, but may pause calling to approach another frog (Owen and Tucker 2006). In Arizona, P. maculata, which is included in the P. triseriata complex (see Comments), have been observed to continue calling while it is snowing, with air temperatures below 0°C, and would temporarily pause calls when vehicles like aircrafts and cars passed by (Bezy and Anderson 2004).

The call of the male is a continuous series of short trills, "prreep-prreep-prreep" (Trauth et al. 2004). Generally calls last 0.8 sec and have an interval of 1.2 sec between each call. There are 17 notes on average per call with an average dominant frequency of 2800 Hz. Notes are typically closer together in the beginning of the call, and the first five notes typically rise in frequency before plateauing. The highest frequency is usually achieved around the 13th note, after which it gradually decreases. The first two thirds of the call generally have a stronger note intensity. Calls vary by temperature, with calls containing fewer notes but occurring at a higher rate in higher temperatures. These shorter calls also have a shorter interval between calls. Behavioral analysis on female response to altered calls indicates that intensity, frequency, duration, and spacing between notes as they occur in natural calls are not necessary to elicit a response. Also, females seem to respond to certain calls based on the combination of features like intensity, frequency, or duration, rather than a few of these properties. Pseudacris triseriata females sometimes respond to calls of P. crucifer, but P. crucifer females do not respond to P. triseriata calls (Martof and Thompson 1964).

In treefrogs, females usually initiate amplexus by making physical contact with males. However, P. triseriata males often initiate amplexus by leaping toward females within a close distance after they approach. Though some females in other species make courtship calls in response to this, no females in any Pseudacris species have been observed to give their own courtship calls (Owen and Tucker 2006).

Anurans including P. triseriata are known to prefer breeding sites where fewer predators are present. Choice of breeding site is especially important for species without parental care or egg defense mechanisms such as protective jelly, as offspring remain defenseless against predators and cannot leave the pond until metamorphosis. In an experiment with the predatory western mosquitofish Gambusia affinis, P. triseriata non-differentially laid eggs in ponds with and without fish. Ponds without fish, however, had almost four times as many P. triseriata eggs as ponds with fish. However, anurans have also shown site fidelity despite predator presence when choosing breeding sites, especially when high-quality breeding sites are long distances (≥10 m) away. The same study showed that there was no significant difference between the number of P. triseriata eggs laid in ponds with predators and conspecific cues (egg masses) both present, ponds with only predators, and ponds with only conspecific cues (Buxton et al. 2017).

Larva
Pseudacris triseriata tadpoles typically live in crowded habitats without predators. They are active, conspicuous feeders and have tail fins that are relatively small for their body size. Tadpoles that constantly feed like P. triseriata tend to have more competitive ability and appear in predator-free habitats, but do poorly when predators are introduced, as rapid development is incompatible with predator avoidance. This is because active movements like feeding attract predators, but tadpoles must feed actively for growth (Smith and Van Buskirk 1995).

A study on the immune response and development of P. triseriata tadpoles to the stress hormone corticosterone revealed that stressed tadpoles undergo development at a faster rate and have much weaker immune systems (Stoltz et al. 2014). Stressors include the presence of predators such as dragonfly naiads. Pseudacris triseriata tadpoles living in the presence of such predators are less active and develop at a faster rate than those living in an environment without predators. Tadpoles undergoing accelerated growth tend to have a smaller size in adulthood, which may have reproductive costs. It is likely that development is sped up in order to allow the tadpole to metamorphose and escape the predators. It has been hypothesized that tadpoles may develop deeper tails in the presence of a predator to aid in escaping faster, but no changes in tail morphology have been observed in P. triseriata tadpoles grown in the presence of predators. Therefore, in P. triseriata, energy is invested in faster development rather than changing tail morphology to allow tadpoles to escape from predators (Smith and Van Buskirk 1995, Lading and Wilcoxen 2021).

Another environmental stressor includes a dry environment. Due to the diminished size of the tail and the emergence of forearms, metamorphosing P. triseriata tadpoles show a decreased ability to swim compared to tadpoles and cannot jump as well as adults (Wassersug and Sperry 1977). In dry periods, P. triseriata larvae are able to adapt by undergoing a shorter larval period, causing them to be smaller at emergence, but resulting in resistance to desiccation and starvation due to the greater availability of terrestrial prey (Whiting 2004).

Tadpole metamorphosis is also affected by the availability of swimmable water. Tadpoles developing in water with constant surface area and decreasing volume (decreasing water level) metamorphosed into larger adults than tadpoles in water with decreasing surface area and constant volume (increasing water level). There is no significant difference in the timing of the start of metamorphosis between these two groups (Durnin and Smith 2001).

Metamorphosis takes place over at least 40 days (Stoltz et al. 2014). A study involving the snake predator Thamnophis sirtalis and P. triseriata showed that the metamorphosing tadpole is the most vulnerable life stage, explaining why anurans have adapted to undergo this transformation quickly in their life cycles (Wassersug and Sperry 1977). The P. triseriata tadpole shows plasticity in development rate depending on environmental stressors, which affects size in adulthood and therefore reproduction (Durnin and Smith 2001, Whiting 2004, Stoltz et al. 2014, Lading and Wilcoxen 2021).

Trends and Threats
Pseudacris triseriata is considered of “Least Concern” on the IUCN Red List. Though the overall population is decreasing, the species is common throughout its range. The species is relatively tolerant to changes in habitat, such as clearing of forests, though wetland loss and other factors have caused population declines. Reforestation efforts may threaten P. triseriata as secondary succession can make breeding grounds unusable (IUCN 2022). Compared to other frog taxa, especially Hyla and Acris, which are also declining in the US, Pseudacris is more stable. It is possible that this is due to the life history of Pseudacris, which avoids water and therefore water-borne diseases for most of its life, dispersing to fields and woods after metamorphosis and only returning to breeding ponds during the brief reproductive period (Moriarty Lemmon et al. 2007).

The first verified case of Batrachochytrium dendrobatidis (Bd) in chorus frogs in the United States was identified in P. sierra, which was misidentified as P. triseriata, collected from the Kawuneeche Valley in Rocky Mountain National Park, Nevada, in June 2001 (Rittman et al. 2003).

Agricultural chemicals have contributed to recent amphibian declines, as they accumulate in the environment, especially wetlands. Atrazine, an herbicide, acts as an endocrine disruptor by inhibiting phosphodiesterase, potentially leading to increased aromatase levels and increased amounts of testosterone converted to estrogen. Generally, increases in Atrazine concentration correlate with increases in proportion of gonadal malformations in P. triseriata, though this trend is not as strong as those observed in Xenopus laevis or Rana pipiens. Gonadal malformations in testes include lobular formation, discontinuous or curved formation, presence of ovarian tissue (hermaphroditism), and presence of oocytes. Control P. triseriata without any Atrazine treatment have not shown severe malformations like discontinuous testes or ovarian tissue growth. It is unknown what happens to larvae with gonadal malformations post-metamorphosis, or whether these abnormalities can be reduced or reversed (Davis 2005).

Possible reasons for amphibian decline

General habitat alteration and loss
Prolonged drought
Secondary succession
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Disease

Comments

PHYLOGENETIC RELATIONSHIPS:

A later study using morphological data, behavioral data, and Bayesian analysis of mitochondrial 12S and 16S rRNA suggest that the trilling chorus frogs—P. brachyphona, P. brimleyi, P. clarkii, P. feriarum, P. kalmi, P. maculata, P. nigrita, and P. triseriata—form a clade in Pseudacris. This analysis shows that P. triseriata is sister to P. ferarium, and the clade containing P. triseriata and P. ferarium is sister to P. kalmi. There is evidence of hybridization between P. triseriata and P. brachyphona (Moriarty Lemmon et al. 2007).

Pseudacris triseriata was previously considered the most geographically widespread anuran in the United States. However, several P. triseriata subspecies are now recognized as full species (Platz and Forester 1988). Pseudacris brachyphona, P. clarkii, P. crucifer, which were all formerly recognized as P. triseriata subspecies, were reclassified as species based on morphological and behavioral data. Pseudacris feriarum, P. kalmi, and P. maculata were elevated to species based on mainly acoustic data (Moriarty Lemmon et al. 2007).

Hybridization between P. triseriata and P. maculata occurs in Illinois within the Big Muddy River, a narrow tension zone where hybrids are selected against (Wang 2017).

References
Bezy, K.B., Bezy, R.L., Bolles, K., and Enderson, E.F. (2004). Breeding behavior of the Western Chorus Frog (Pseudacris triseriata complex) in Arizona do Chorus Frogs call in the snow on the Colorado Plateau? Sonoran Herpetologist, 17(8), 82-85. [link]

Buxton V.L., Ward M.P., and Sperry J.H. (2017). Frog breeding pond selection in response to predators and conspecific cues. Ethology, 123(5), 397–404. [link]

Cope, E.D. (1889). Chorophilus triseriatus. Bulletin of the United States Museum, 34, 342-352. [link]

Davis, M. (2005). Gonadal effects of Atrazine in two North American species of frogs: Rana pipiens and Pseudacris triseriata. Master’s thesis, North Dakota State University. ResearchGate. [link]

Duffitt, A.D., and Finkler, M.S. (2011). Sex-related differences in somatic stored energy reserves of Pseudacris crucifer and Pseudacris triseriata during the early breeding season. Journal of Herpetology, 45(2), 224-229. [link]

Durnin, K.B., and Smith, G.R. (2001). Effects of changing water volume on the tadpoles of two anuran species (Pseudacris triseriata and Rana blairi). Journal of Freshwater Ecology, 16(3), 411–414. [link]

Ethier, J.P., Fayard, A., Soroye, P., Choi, D., Mazerolle, M.J., and Trudeau, V.L. (2021). Life history traits and reproductive ecology of North American chorus frogs of the genus Pseudacris (Hylidae). Frontiers in Zoology, 18, 40. [link]

Frost, D. (2024). Pseudacris triseriata (Wied-Neuwied, 1838). Amphibian Species of the World. https://amphibiansoftheworld.amnh.org/Amphibia/Anura/Hylidae/Hylinae/Pseudacris/Pseudacris-triseriata. Accessed on 18 November 2024.

Hurter, J. (1911). Herpetology of Missouri. Transactions of the Academy of Science of Saint Louis, 20(5), 59-274. [link]

INHS Herpetology Collection. Trilling Chorus Frogs. University of Illinois Urbana-Champaign. https://herpetology.inhs.illinois.edu/species-lists/ilspecies/trilling-chorus-frogs/ Accessed on 5 November 2024

IUCN SSC Amphibian Specialist Group. 2022. Pseudacris triseriata. The IUCN Red List of Threatened Species 2022: e.T55899A193395385. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T55899A193395385.en. Accessed on 04 March 2024.

Lading, H., and Wilcoxen, T.E. (2021). Western chorus frog tadpoles (Pseudacris triseriata) show expedited development, but no change in tail morphology, in the presence of predators and independent of diet. BIOS, 92(1), 1-7. [link]

Martof, B. S., and Thompson, E. F. (1964). A behavioral analysis of the mating call of the Chorus Frog, Pseudacris triseriata. The American Midland Naturalist, 71(1), 198–209. [link]

Matthews, T., and Pettus, D. (1966). Color inheritance in Pseudacris triseriata. Herpetologica, 22(4), 269–275. [link]

Moriarty-Lemmon, E.C., Lemmon, A.R., Collins, J.T., Lee-Yaw, J.A., and Cannatella, D.C. (2007). Phylogeny-based delimitation of species boundaries and contact zones in the trilling chorus frogs (Pseudacris), Molecular Phylogenetics and Evolution, 44(3), 1068-1082. [link]

Moriarty, E.C., and Cannatella, D.C. (2004). Phylogenetic relationships of the North American chorus frogs (Pseudacris: Hylidae), Molecular Phylogenetics and Evolution, 30(2), 409-420. [link]

Owen, P.C. and Tucker, J.K. (2006). Courtship calls and behavior in two species of chorus frogs, genus Pseudacris (anura: Hylidae). Copeia, 2006(1),137-144. [link]

Platz, J. E., and Forester, D. C. (1988). Geographic variation in mating call among the four subspecies of the Chorus Frog: Pseudacris triseriata (Wied). Copeia, 1988(4), 1062–1066. [link]

Platz, J. E. (1989). Speciation within the Chorus Frog Pseudacris triseriata: morphometric and mating call analyses of the Boreal and Western subspecies. Copeia, 1989(3), 704–712. [link]

Powell, R., Conant, R., and Collins, J.T. (1998). Peterson Field Guide To Reptiles And Amphibians Eastern and Central North America. Mariner Books.

Rittman, S.E., Muths, E., and Green, D.E. (2003). Pseudacris triseriata (Western Chorus Frog) and Rana sylvatica (Wood Frog) chytridiomycosis. Herpetological Review 34(1), 53. [download]

Rogic, A., Tessier, N., Noël, S., Gendron, A., Branchaud, A. and Lapointe, F.-J. (2015). A “trilling” case of mistaken identity: call playbacks and mitochondrial DNA identify chorus frogs in southern Québec (Canada) as Pseudacris maculata and not P. triseriata. Herpetological Review, 46(1), 1–7. [download]

Smith, D. C., and Van Buskirk, J. (1995). Phenotypic design, plasticity, and ecological performance in two tadpole species. The American Naturalist, 145(2), 211–233. [link]

Smith, W.H. (1882). Report on the Reptiles and Amphibians of Ohio. Columbus: Nevins and Meyers. [link]

Stoltz, K., Carlson, R., and Wilcoxen, E. (2014). Effects of corticosterone on development and immunocompetence in Western Chorus Frogs (Pseudacris triseriata) and Southern Leopard Frogs (Lithobates sphenocephalus). BIOS, 86(2), 91-98. [link]

Trauth, S.E., Robinson, H.W., and Plummer, M.V. (2004). The Amphibians and Reptiles of Arkansas. University of Arkansas Press.

Wang, A. (2017). Two species contact zone of Pseudacris maculata and Pseudacris triseriata. Bachelor Thesis, Florida State University. FSU Digital Repository University Libraries. http://purl.flvc.org/fsu/fd/FSU_libsubv1_scholarship_submission_1512749504_22b38fc4

Wassersug, R.J. and Sperry, D.G. (1977). The relationships of locomotion to differential predation on Pseudacris triseriata (Anura: Hylidae). Ecology, 58: 830-839. [link]

Whiting, A. (2004). Population ecology of the western chorus frog, Pseudacris triseriata. Master’s Thesis, McGill University. eScholarship. https://escholarship.mcgill.ca/concern/theses/9s1616759

Species Account Citation: AmphibiaWeb 2024 Pseudacris triseriata: Midland Chorus Frog <https://amphibiaweb.org/species/1061> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

AmphibiaWeb's policy on data use.