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Scientific name: Pseudoacris crucifer
Common name: 
Spring Peeper

(Information for this species page was gathered in part by Sheila Chadman (2001), Kristy Grande (2004), and Jennifer Rusnak (2005) for Biology 220W at Penn State New Kensington).

One of the truly great signs of early spring is the rolling, night time chorus of the Spring Peeper. This tiny frog is found throughout much of North America and is especially abundant in the eastern United States. The Peeper’s scientific name, Pseudoacris crucifer, means “false locust” (for its insect-like call), and “cross” (for the distinctive X-shaped marking on its back). It is found in a variety of colors from yellow to olive green and gray to brown, and lives in marshes, ponds, wet meadows, and temporary pools throughout the United States with the exception of southern Georgia and Florida. The Spring Peeper is a tree frog and possesses toe pads that help it to climb the trees, shrubs, and tall grasses that surround its ponds. It is from these perches that male frogs sing their distinctive mating songs. 

Mating Call
The mating choruses begin in early spring typically 15 minutes or so after sundown. The calls require a very large expenditure of energy by each individual which may explain why the males bunch together to form a large, high volume ensemble (even though it greatly intensifies mating competition between individuals). Each frog is able maximally to make 90 calls a minute over a four hour chorus time. The mating/calling season only lasts for 4 to 8 weeks. Male peepers begin to sing when they are three years old and the age, size, and overall health of the frog greatly affect the calling frequency. The temperature of the evening also affects calling patterns. On warmer evenings the frogs call much more frequently.

Mating and Reproduction
Females are attracted to the calling of the males and upon entering the calling area select the individual with whom they want to mate by nudging him. The male then clasps himself onto the female’s back and remains there through mating and even on to the female’s return to the pond to deposit her eggs. The attached male prevents other males from mating with the female and insures that all of the female’s eggs will be fertilized by his sperm. The female can lay between 800 and 1000 brown-colored eggs which may be deposited singly or in groups in the pond water, attached to submerged vegetation, in the mud, in fluid filled tree hollows, or in other types of micro-pools. 

The eggs take between 6 to 12 days to hatch. The larval frogs that emerge from the eggs (the “tadpoles”) are short with prominent dorsal fins. The tadpoles will remain in their aquatic form typically for 90 to 100 days. This larval incubation can, however, be as short as 45 to 60 days depending upon weather conditions, time of egg laying, and conditions in the tadpole’s pool. Populations of peepers being reared in temporary pools may be undergoing selection for shorter and shorter larval incubation times. The devastating effect of the drying up of the pool is an unforgiving selection force.  The tadpoles eat a wide variety of foods (including algae, dead vegetation, bacteria, fungi, zooplankton, flesh from animal carcasses, and even inorganic materials like sand). The tadpoles are in turn preyed upon by almost any organism that is larger than they are. Fish are especially significant tadpole predators in ponds, but predaceous beetles, salamanders, and water snakes also readily consume the tadpoles. Further, pesticides and other pollutants (including acid rain) are also significant agents of mortality in spring peeper tadpoles.

Metamorphosis to Adult Form
The metamorphosis of the tadpole into a frog begins with the appearance of hindlimbs which is followed by the emergence of the forelimbs and the shrinkage of the tail. Jaws with teeth, eyelids, mucous glands in the skin, and finally the transformation of the light cartilaginous skeleton of the tadpole into the denser, bony skeleton of the frog complete the metamorphic transition into a tiny frog. The emergence of the frog onto land exposes it to even more predators and environmental dangers. The frogs are readily eaten by snakes, turtles, birds, and mammals like chipmunks and muskrats. They are also frequently killed on roadways by passing cars and trucks. Peepers are also susceptible to many viral and bacterial illnesses, exhibit a wide range of benign and cancerous skin and mucous membrane tumors, and are beset by a wide range of endo- and ectoparasites (including tapeworms, flukes, nematodes, protists, and larvae of several dipteran species. Destruction of their aquatic habitats, and even more subtle alterations of the forest cover around their wetland breeding sites can deleteriously affect the breeding potentials and survival of this small amphibian.

Hibernation
The Spring Peeper over-winters in an inactive, hibernative state under soil and leaf litter, in and under rotting logs, and even under rocks. They are frequently exposed to sub-freezing temperatures during their winter hibernation and are able to insure their survival in a frozen state by generating large quantities of glucose from their livers. This sugar acts as a natural anti-freeze in their blood and other body fluids. Survival during these sub-freezing events is inversely related to the duration of the exposure (85% of the frogs survive after 3 days of freezing, about 50% survive after 7 days of freezing, and 0% survive after 28 days of freezing). While the peeper is in its hibernative state they continue to be exposed to predation pressures. Shrews, for example, burrowing about under the soil or in the subnivian spaces readily consume the inactive frogs.  



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