The spring peeper (Pseudacris crucifer)[3] is a small chorus frog widespread throughout the eastern United States and Canada.

[4] It prefers permanent ponds due to its advantage in avoiding predation; however, it is very adaptable with respect to the habitat it can live in.

In northern regions, the frog is able to endure below freezing temperatures due to the capacity of its liver to exude and flush the bloodstream with a glucose cryoprotectant which acts both as an anti-freeze in its blood, and allows organs like the heart to enter into a state of protected dormancy.

Crucifer is derived from the Latin root meaning "cross-bearing", a reference to the cross-like pattern on the spring peeper's dorsal side.

[6] The spring peeper is a tan or brown frog with a dark cross on its dorsa (thus the Latin name crucifer, meaning cross-bearer[7]), though sometimes the marking may be indistinct.

[10] The species has large toe pads for climbing, although it is more at home amid the loose debris of the forest floor.

[13] This frog has a vocal sac that expands and deflates like a balloon to create a short and distinct peeping sound.

[12] In Hyla crucifer males, the blackened pigmentation of the testis affects the seminiferous tubules, the underside of the peritoneum, and the organ itself.

After the seminiferous tubules are emptied, during mating season, the pigmentation of the testis changes from black to a dull grey.

Stored reserves of fat and glycogen contents can be measured early in the reproductive process to determine the amount used in spring peepers and their correlation to body size.

Nonpolar lipid and glycogen content in male spring peepers increased with body mass, whereas in females, it decreased or had minimal variation.

At the beginning of the breeding season, male spring peepers have more significant amounts of bodily lipid content.

These types of males utilize citrate synthase and β-hydroxyacyl CoA dehydrogenase in their muscles at greater levels.

Males with higher calling rates also tend to inhibit larger ventricles and greater concentrations of blood hemoglobin; both the large ventricle size and blood hemoglobin concentrations play a significant role in the speed of oxygen consumption, which is intensely linked to the calling rate.

[15] When a male spring peeper calls, the sound is made by the contraction of external and internal oblique muscles which subsequently force air out of the lungs, then move through the larynx to the vocal sac.

Its northern conspecific occurs in the entire east of the Mississippi and ranges to the Atlantic provinces in Canada as far west as Saskatchewan.

[25] This amphibious species requires marshes, ponds, or swamp regions to support the aquatic environment the eggs and tadpoles need.

In the northern reaches of their range, spring peepers must endure occasional periods of subfreezing temperatures during the breeding season.

The species can tolerate the freezing of some of its body fluids, and undergoes hibernation under logs or behind loose bark on trees.

[26] The mating displays of male spring peepers vary with different environmental factors: humidity and vegetation density.

At sites with higher humidity and air temperature, there is increased dominance of arboreal behavior, which showcases that latitude may play a role.

Spring peepers are nocturnal insectivores, emerging at night to feed primarily on small invertebrates, such as beetles, ants, flies, and spiders.

[9] The spring peeper's diet involves the filtering of particles from water columns and scouring periphyton and detritus (dead, organic matter) from environmental surfaces in their habitat.

During the first season of breeding, the two-year-old males produce higher frequency calls than males in their third and fourth seasons do [34]As their common name implies, the spring peeper has a high-pitched call similar to that of a young chicken, only much louder and rising slightly in tone.

[6] The mating calls of the spring peeper consist of a sound very similar to a "peep" and are repeated by males up to 13,500 times per night.

[41] These satellite males are also known to circumvent female choice and increase rates of hybridization between spring peeper lineages.

[19] Spring peepers predators include great diving beetle larvae (when in tadpole form), snakes, skunks, and larger frogs.

[43] Drying periods of ponds typically align before or during the metamorphic larval stage of spring peepers due to their slower growth rates.

Larval spring peepers harvest smaller amounts of resources, resulting in them having lower metabolic costs and a maintained growth rate.