Who is the Pickerel Frog?

The Pickerel Frog is a medium sized gray or tan frog marked with seven to twenty-one irregular rectangular dark brown spots which are oriented in two columns down its back (Nova Scotia Museum of Natural History website). Prominent dorsolateral ridges and yellow or white lines also run down the back. A light line extends along the upper jaw, and its hind legs are banded. The northern populations tend toward a plain whitish color, while the Coastal Plain populations are usually mottled with dark splotches. These colors blend in well with the foliage of its habitat, making it easy for the Pickerel Frog to camouflage itself. Adult males range between 4.4cm and 5.8cm. Females are slightly larger, and can grow as large as 7.9cm. The largest recorded Pickerel Frog was 8.7cm (Conant and Collins 345).

Pickerel Frog (left) vs Leopard Frog (right)
      The Pickerel Frog is often confused with the Leopard Frog, Rana pipiens . They are found in similar areas, and many populations of both species are found to peacefully cohabitate. Indeed, some hybridization has reportedly taken place (Conant and Collins 341). But the Pickerel Frog is a distinct species, and should not be mistaken for Rana pipiens. The Pickerel Frog can be distinguished by the bright yellow or orange coloration on the concealed surfaces of the hind legs and belly (see photo at right). With the exception of the Plains Leopard Frog, Rana blairi, Leopard Frogs lack this bright coloration. Also, unlike the Pickerel Frogs, who have rectangular splotches, Leopard Frogs have circular or oval spots on their backsides (see photo at left).
Pickerel Frog underbelly

      To remain healthy, Pickerel Frogs eat a balanced diet of ants, spiders, bugs, beetles, sawfly larvae, and other invertebrates. To find and catch these critters, Pickerel Frogs search the grassy areas next to streams. In case of attack, Pickerel Frogs have an excellent defense mechanism: they emit skin secretions which are irritating to people and toxic to some predators. This toxicity makes the Pickerel Frog the only poisonous frog native to the United States. Because of this, most snakes and mammals will leave Pickerel frogs alone. Still, this frog does have some predators. Green Frogs and Bullfrogs, for example, have developed immunities to the secretions, and are always happy to munch on a Pickerel Frog snack. And in fact, the name "Pickerel Frog" was coined because this frog often served fishermen well as their bait for the predatory Pickerel Fish. However, despite the Pickerel Fish's fondness for Rana palustris soup, it must be noted that in this case the real predator is, of course, Man and not the Pickerel Fish, for it is Man who catches these frogs and places them on the fishing line. And unfortunately for the Pickerel Frog, a small amount of skin toxin will not stop Homo sapien.

      The habitat of the Pickerel Frog is relatively varied. In the north, they live in cool, clear water. These northern specimens especially enjoy bogs, rocky ravines, and meadow streams but can be found in other habitats as well. In the South, they reside in the warm water of the Coastal Plain and floodplain swamps. Although these frogs are often found in aquatic environments, their toes are unwebbed. This morphological characteristic is a feature of all frogs in the genus Rana, and helps to make them equally fit for terrestrial life. Pickerel Frogs are most often seen along the edges of streams or flooded ditches, but they can also be found in caves and sometimes on the roadsides. If disturbed, they will jump into the water and quickly dive to the bottom. Pickerel Frogs often live happily alongside other species of frogs. In water habitats, you might them cohabitating with Mink Frogs (Rana Septentrionalis). On land, keep an eye out for the Northern Leopard Frog (Rana pipiens).

      In the winter, Pickerel Frogs hibernate under the bottom debris and silt of their aquatic habitats, so they are active only from April to October. At this time of year, Pickerel Frogs inhabit wooded stream areas with a dense forest canopy. After they have finished breeding, Pickerel Frogs will venture on land deep into grassy fields and weed-covered areas. Along with periodically reducing activity (controlling your metabolism is one of the perks of being an ectotherm!), choosing to reside in areas with thick foliage ensures that these frogs will not overheat when the high-temperature months of summer roll around. The earliest Spring record of a Pickerel Frog sighting is April 5th, 1975. This female specimen was found on a wet highway after midnight in Princedale, Annapolis County. The latest Fall sighting is October 30th, 1935 at East Roman Valley in Guysborough County (Nova Scotia Museum of Natural History website).

Range Map for the United States
      To the West, Pickerel Frogs can be found in the Wisconsin and Southeast Minnesota areas, eastern Iowa through Missouri, and down to eastern Texas. They are mostly absent in the Illinois, Ohio, and Indiana areas. To the South, they range through Northern Louisiana, Mississippi, Northern Alabama, Georgia and South Carolina. And to the North, their habitat runs all the way up through the Northeast, statewide in Connecticut, and into Canada. In Canada Pickerel Frogs can be found in Ontario, New Brunswick, and Nova Scotia.

Range Map for Maine

Range Map for Minnesota
Pickerel Frogs are not at all evenly distributed through the areas they inhabit. As these range maps demonstrate, for instance, Pickerel Frogs are found almost everywhere in Maine. In contrast, they are only found in the southeasternmost portion of Minnesota. This is a small example of the larger fact that while these frogs are extremely widespread throughout the northeastern United States (including in Connecticut!) and up into Canada, they are much less abundant in the the midwest.

      The breeding season of the Pickerel Frog lasts from March to May, usually beginning as Leopard Frogs are concluding their breeding activity for the year. I say usually, because, as I mentioned earlier, research does indicate a small amount of Leopard and Pickerel Frog hybridization. Therefore their breeding seasons must overlap to some degree! Pickerel Frog males find mates by calling: Above water, they call from on top of vegetation mounds; when under water, they call from among submerged branches or areas of thick vegetation. In order to produce their steady but weak low-pitched croak lasting 1-2 seconds, male Pickerel Frogs use their paired vocal sacs. When they call from under the water, which they often do, their call sounds like a low-pitched snore. The dominant frequency of this snore is usually around 2100 Hz (Cleveland Museum of Natural History website). In addition to their advertisement call, with which males attract females, Pickerel Frogs have a distinct aggressive call as well. This chuckling noise, also produced by the male, serves as a warning to another male that he may be infringing upon the first male's territory (UCONN Museum of Natural History website). To hear the Pickerel Frog's advertisement call, click here.

Spectrogram of the Pickerel Frog Call

      In areas where Pickerel Frog populations are large and numerous, such as the northeastern United States, mating pairs can be found almost everywhere in April and May. For example, as the figure on the right shows, breeding season in Maine brings state-wide mating. Male Pickerel Frogs have stout forearms and, during breeding season, the thumbs on their forelegs swell so they can hold on to the female during amplexus. Indeed, if you go to the temporary and permanent ponds where Pickerel Frog amplexus occurs, you will be able to identify these breeding males by their swollen thumbs.
      Pickerel Frogs are oviparous creatures, and they will select ponds with dense shrubs in which to lay their eggs. Pickerel Frogs need these shrubs so that they can attach their firm globular egg masses to branches about 10cm below the surface at the edge of the pond in shallow water. Pickerel Frogs may also lay their eggs in bogs or marshes. Each frog lays approximately 2-3 thousand eggs in the course of several egg masses. Because they are submerged, these egg masses are very difficult for the average naturalist to find, and are rarely spotted. Within the egg mass, each egg is, on average, 1.7mm in diameter when laid. The eggs are brown and yellow, and consist of two jelly envelopes, the outermost of which is approximately 4mm in diameter, wrapped around a central black dot. The olive green tadpoles are large and elongate, and mottled with fine black and yellow spots. The tadpoles' tails are darker than their bodies, and are marked with large yellow spots (Catalogue of Amer. Amphib. and Reptiles 117.1). Metamorphosis out of the tadpole stage occurs 87-95 days after the eggs are laid, usually in August and September. At this point, juveniles 19-26mm in length can be found under rocks or next to creeks and ponds. These juveniles possess a slightly metallic shine but lack the bright yellow and orange coloration found in adults. Also, the lower lip of the juvneiles is clouded with a darker color. At two years of age these young Pickerels are sexually mature, which means that they are ready to breed, and thus to start the life cycle all over again.

Areas of Pickerel Frog breeding in Maine (top figure) and around the United States (bottom figure) Northeast

Conservation Information...

      Fortunately, the Pickerel Frog remains a fairly secure species at the moment. Especially in Connecticut and throughout the United States Northeast, Pickerel Frogs abound. Curiously, the Pickerel Frog's close relative, the Leopard Frog, is not faring nearly as well. In some localities where the two species cohabitate, Leopard Frogs are abundant. Yet in other localities we find Pickerel Frogs everywhere and simultaneously discover that Leopard Frogs are startlingly absent from the area. More research is needed to determine the cause of this phenomenon. However, despite the Pickerel Frog's relative survival success, like all wildlife, this frog is not out of danger. Rana palustris has been seen to do particularly poorly in more urbanized and polluted areas. For example, because of its high level of pollution, the Great Lakes area is home to very few Pickerel Frogs. And unfortunately, urbanization is taking place everywhere, so this frog's safety is not guaranteed. Still, conservation projects like the Rogue River National Wet Weather Conservation Project are beginning to clean up the pollution, and are thus helping to maintain the survival of such amphibian species as Rana palustris.

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