The pickerel frog is a medium-sized frog with a wide ridge of skin (dorsolateral fold) along each side of the back, and two parallel rows of squarish or rectangular spots running down the back between the folds. The general color is gray, tan, or brown. A white line is present along the upper lip. The distinct dorsolateral fold extends down to the groin and may be white, cream, gray, yellow, or golden. The spots on the back are reddish brown, dark brown, or black. Dark bars on the hind legs are prominent. The underside of the hind legs and groin area are washed with bright yellow, orange yellow, or pink yellow. The belly is white.
The call of male pickerel frogs is a low-pitched, descending snore lasting a couple of seconds. Although this frog calls from above water like most other frog and toad species, a number of observers have reported this frog vocalizing while under water.
Similar species: Missouri’s three species of leopard frogs lack the pickerel frog's combination of having wide, unbroken skin folds along the back; two distinct rows of square or rectangular spots down the back; and yellow or orange-yellow coloration along the underside of the hind legs and groin area.
Missouri has eight members of the true frog family. These are typically medium- to large-sized, have long legs, smooth skin, and well-developed webbing between the hind toes. Another common characteristic is a glandular fold or ridge of skin along each side of the back (these are called dorsolateral folds).
Adult length (snout to vent): 1¾ to 3 inches; occasionally to 3½ inches. Adult males are generally smaller than adult females.
Common in southern and eastern Missouri. Absent from the northwestern third.
Habitat and Conservation
The pickerel frog is generally associated with springs, cold streams, and cool, shaded woodland ponds. In Missouri, it occurs along Ozark streams under rocks at the water’s edge. Pickerel frogs also live along streams in grassy areas, pastures, and near farm ponds, along shaded ravines in forests, in moist grassy fens, and under rocks on glades during the spring. In eastern Missouri along the Mississippi River, this species is associated with springs and creeks that flow from limestone bluffs. During the hot summer months in central Missouri, this frog is often seen in and around wet areas of yards, gardens, and water fountains.
Pickerel frogs have a high association with caves, especially the cave entrances. They use wet caves as a refuge from hot weather during late summer, and from cold temperatures during winter. This is the only species of frog in Missouri that takes shelter in caves with regularity and in high numbers; a single cave may harbor hundreds of pickerel frogs. The relatively constant temperature and moisture in a wet cave provide an ideal site for overwintering. The frogs may exit for short periods of time to feed, but from late September to early November, they will have moved to a deeper section of the cave where the temperature is more stable. Here they remain until spring.
During March or early April, the frogs leave the caves and locate a woodland pond, slough, or water-filled ditch for breeding. The frogs feed during the spring and summer; some begin to return to the cave in late July. Young-of-the-year pickerel frogs were found to have the greatest mortality during the winter.
In some areas, this species overwinters in springs, in mud at the bottom of streams or ponds, and under large stones along the margins of small streams.
Even though pickerel frogs occupy somewhat specialized habitats of cool water springs, streams, and caves, they appear to be common throughout the karst, forested habitats of Missouri. This species is typically underrepresented in calling surveys but is commonly observed on land throughout much of its active season.
Food
Pickerel frogs eat a variety of invertebrates, including ants, spiders, beetles, moth larvae, sowbugs, crickets, and earthworms.
Status
Taxonomy: The true frog family (Ranidae) is the largest and most widespread family of frogs. It contains 365 species in 14 genera and probably originated in Africa. Representatives of this cosmopolitan family occur on every major land mass except New Zealand, Antarctica, most oceanic islands, the West Indies, and southern South America. The largest genus in the family in the New World (North and South America) is Lithobates (formerly Rana), with about 50 species. Missouri’s species, formerly in genus Rana, are all in genus Lithobates. As of taxonomic understandings in 2016, the Rana genus is considered restricted to the eastern hemisphere and western North America. In Missouri, the genus Lithobates is represented by eight species.
Life Cycle
Breeding occurs March through May, in fishless woodland ponds, sloughs, and water-filled ditches. Peak chorusing is from mid-April to early May. Females lay from 700 to 2,900 eggs in shallow water in a globular mass attached to a submerged stick or stem. The tadpoles hatch in 10 days or more, and they transform into froglets after 3½–4 months. The transformation is complete around mid-July to mid-August. Development time varies with temperature.
Human Connections
Frogs help control populations of sometimes-troublesome insects. Because they are sensitive to pollutants, they are considered indicator species whose health and numbers can be a way to gauge the health of their ecosystem.
Caves are delicate ecosystems, and to protect the many species that live in them, it is recommended that people refrain from entering caves. Also, teach yourself about groundwater ecology and learn ways to protect caves, springs, sinkholes, and other underground habitats.
Ecosystem Connections
Frogs are predators that help keep populations of insects and other small animals in balance. They, and especially their eggs, tadpoles, and young froglets, become food for both aquatic and terrestrial predators ranging from water bugs to fish to grackles to raccoons.
Skin secretions of pickerel frogs are known to be irritating or even toxic to small animals. If newly captured pickerel frogs are placed in the same container with other frog species, the latter will die within a short time due to these skin secretions. These secretions appear to be a defense against predation. Most frog-eating snakes will not eat pickerel frogs. A study in west-central Kentucky showed that pickerel frogs that breed in ponds where fish are present are likely to be more toxic than frogs that breed in fishless ponds.
