Spring Peeper

The spring peeper (''Pseudacris crucifer'') is a small chorus frog widespread throughout the eastern United States and Canada. They prefer permanent ponds due to their advantage in avoiding predation; however, they are very adaptable with respect to the habitat they can live in. Due to their presence in northern regions, the frog is able to endure below freezing temperatures. They are so called because of their chirping call that marks the beginning of spring. ''Crucifer'' is derived from the Latin root meaning "cross-bearing." This could be a reference to the cross-like pattern on the spring peeper's dorsal side.

These chirping calls are significant for communication in mating as females choose their mates based on the frequency and volume associated with them. Satellite males who do not make any calls also strategically place themselves near those that make louder calls in an attempt to intercept females.

Temperature plays a large role in when the spring peeper begins breeding as well as the duration of mating calls. Therefore, climate change has the ability to significantly impact this species in the near future.

Description

Spring peepers are tan or brown frog with a dark cross on their dorsa (thus the Latin name ''crucifer'', meaning cross-bearer), though sometimes the marking may be indistinct. They have a body length between less than to and a mass between .

Anatomy and Physiology

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

The color variations of ''P. crucifer'' are mostly tan, brown, olive green, and gray. All have a slightly pale yellow coloration on the inside of the thighs. Females are lighter-colored, while males are slightly smaller and usually have dark throats. Females have a bulkier abdomen. Skin color of Spring Peepers is also affected by temperature and light. Coloration is dynamic and adaptable in this species. It can be altered quickly, in 15 to 45 minutes, in order to better camouflage from predators.

This frog has a vocal sac that expands and deflates like a balloon to create a short and distinct peeping sound. Only males can make this loud high-pitched noise, and they use it to attract mates.

File:Spring peeper-Florida.jpg, Spring peeper, adult, Florida
File:Spring peeper.jpg, Spring peepers are distinguished by a dark X-shaped marking on their back.
File:Pseudacris crucifer.jpg, Spring peeper, adult
File:Pseudacris crucifer01.jpg, Spring peeper, adult
In the female spring peeper, protruding beyond the lower jaw of the frog sits its snout. Through the use of adhesive pads located on the tips of their non-webbed fingers, spring peepers can stick to particular materials. Males and females are differentiated from one another through the darkening of the skin beneath the jaw in males. Males have a body length ranging from 18-30mm, and females have a body length ranging from 20-35mm.

Glands and Toxins

In Hyla crucifer males, the blackened pigmentation of the testis affects the seminiferous tubules, the underside of the peritoneum, and the organ itself. The tubules of the testis are surrounded by a pigment layer and a layer of flattened epithelial cells which are located within the surrounding connective tissue. The thickness of an average testis is about 1.10 mm and 2.5 mm in length. The spermatogonia are a cluster of masses jutting out from the tubule lumen. In the late fall, the spermatozoa, located in the seminiferous tubules of the spring peeper, mature and remain there until the spring for breeding. After the seminiferous tubules are emptied, during mating season, the pigmentation of the testis changes from black to a dull grey.

In the spring peeper, most of its energy is used during courtship. Higher energetic costs in female spring peepers are associated with gametogenesis, which occurs before breeding. 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. The fiber triglyceride and glycogen contents of the female spring peeper's liver increased significantly slower than males as body mass increased. At the beginning of the breeding season, male spring peepers have more significant amounts of bodily lipid content. Therefore, those that are larger are experiencing lower efficiencies in calling. More reserves of glycogen and lipids are required to maintain calling during the season and require additional rationing of reserves to prepare themselves for courtship. In females, there is a positive correlation between their snout length and wet ovary mass, which also correlates to an increase in body size.

Respiratory and Circulatory System

The bigger, older, and more fit male spring peepers are typically superior callers. These types of males utilize citrate synthase and β-hydroxy acyl CoA dehydrogenase (a protein) 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. 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. Of the total body weight of male spring peepers, 15% is made up of the trunk muscles – which contain 2% of lipids in the body by volume – and showcase enzymes with mitochondrial markers. Calls that occur at rapid rates result in prominent energetic costs, which is why stored lipids are the source of 90% of energy applied to calling.

Thermoregulation

Due to climate playing a major role in when spring peepers begin breeding, one can determine that there is a clear association between temperature and breeding. Spring peepers begin to bread during temperatures that are warmer, showcasing a positive correlation between temperature and breeding time. Amphibians are exotherms, which shows that any change in the typical climate of their environment would leave spring peepers in a vulnerable position. Temperature increases can significantly impact reproduction-assigned behavior considerably.

Another impact of temperature is the duration of mating calls. There is a negative relationship between the length of mating calls and throat temperature. However, male spring peepers with superior calling frequencies are positively related to throat temperature. The temperature of the surrounding environment of spring peepers also plays a role in the rate of calls, which is positively associated with the success of males during the mating and breeding period, showing that increasing site and throat temperatures result in increasing dominant frequency.

Geographic Range and Habitat

The southern spring peeper's habitat includes the Gulf Coast from southeastern Texas to southeastern Georgia and northern Florida, United States. Its northern conspecific occurs in the entire east of the Mississippi and spreads to eastern and central Canada.

During the breeding season, the spring peeper will be found near ponds and usually located in bodies of water that are free of fish and pollutants. During actual breeding, their choruses form near where trees hang by bushy plants or secondary forests. Their choruses can also be located within ponds, marshes, or swamps. They will usually resume call activity during warm rain, and are not commonly seen outside of their breeding choruses. During the non-breeding season, they will inhabit dead plant material from trees, shrubs, and other plants in the woods.

Spring peepers are often found in temporary ponds (which eventually dry during the summer months), intermediate ponds that have interchanging periods of being dry and wet every year, or in customarily filled ponds year-round. Although they are able to inhabit multiple types of ponds, spring peepers have been seen to be superior competitors in permanent ponds due to their higher caliber of predation resistance within the environment. Spring peepers live primarily in forests and regenerating woodlands near ephemeral or semipermanent wetlands. 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. It is capable of surviving the freezing of its internal body fluids to temperatures as low as -8 °C (17.6 °F). This species frequently occurs in breeding aggregations of several hundred individuals, and commonly breeds in many small wetlands, including swamps and temporary pools and disturbed habitats, such as farm ponds and borrow pits.

Home Range and Territoriality

The mating displays of male spring peepers vary with different environmental factors: humidity and vegetation density. These factors play a significant role in the arboreal behavior and nature of spring peepers during mating. At sites with higher humanity and air temperature, there is increased dominance of arboreal behavior, which showcases that latitude may play a role. Spring peepers who reside in areas of warmer temperatures tend to exhibit arboreal behavior to greater extents compared to those in environments of lower temperatures. When comparing the improvement of mating calls in males, calls from above ground compared to those near the ground showcased better results. Local vegetation may also play a role in the betterment of arboreal calling compared to calling from lower levels due to the spatial aspects interrupting the call.

Diet

Juvenile

Tadpoles are suspension feeders, therefore they graze on inorganic and organic matter. They also feed on algae and other organisms in the water. Their predators include great diving beetle larvae (when in tadpole form), snakes, skunks, and larger frogs.

Adult

Spring peepers are nocturnal insectivores, emerging at night to feed primarily on small invertebrates, such as beetles, ants, flies, and spiders. They do not climb high into trees, but hunt in low vegetation. Spring peepers living in deep, damp forests are active hunters both day and night, whereas those found in woodland edges restrict most hunting and other activity to night. 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.

Reproduction and Life Cycle

Brood size

Spring peepers breed in southern areas from October to March, depending on the local temperature. In northern areas, they breed between March and June, when the warm rains start. ''P. crucifer'' typically lays around 900 eggs per clutch, but up to 1000 are possible. Egg clusters are hidden under vegetation or debris at the water base. In very cold weather, they hibernate under lo