pickerel frog PICKEREL FROG
Rana palustris
 
INTRODUCTION
Pickerel frogs are common throughout the state; whereas the less common leopard frog (Rana pipiens) occurs only on the eastern shores and some islands of Narragansett Bay (Klemens 1993). For some reason, people who encounter pickerel frogs often assume that they have found a leopard frog, perhaps the name leopard and the dorsal spot pattern of the two frogs is an easier association than the name pickerel. The two species are similar in appearance, but can be separated by a few characteristics that are described in the identification section.

Pickerel frogs spend most of their lives out of water, even during the breeding season. They only enter the water to avoid predation (from birds and snakes), to lay eggs, and to thermo-regulate (Dickerson 1906). For most of the year, aside from winter months when they hibernate, they can be encountered moving across the landscape. Favorite habitats include moist woods with multiple cool running streams.

 
IDENTIFICATION

  • Frequently confused with the less common leopard frog (Rana pipens). In Rhode Island leopard frogs are only found on Aquidneck Island (Newport and Portsmouth), Conanicut Islands (Jamestown), and the east side of Narragansett Bay (Klemens 1993).
  • Pickerel frogs have a bronze to light brown dorsal ground color with irregular shaped-squarish spots arranged in two lines down their back. Colors are more brilliant in juveniles (Klemens 1993).
  • The spots are bicolored-iridescent rusty brown surrounded by black.
  • The leopard frog is similarly spotted, however the spots are more circular, surrounded by a lighter colored border, and are not neatly arranged (Klemens 1993).
  • A relatively thick white to yellow line parallels each dorsal-lateral ridge. Below this line are more irregular spots.
  • The back legs are boldly banded; the underside of the legs is bright yellow to orange. Leopard frogs lacks this bright color.
  • The venter is white.
  • A prominent white line outlines the upper jaw.
pickerel frog
Pickerel frog dorsal view

Sexual dimorphism

  • Female pickerel frogs are larger and typically darker in color than males (Mairs 1999).
  • The male can be recognized by its swollen thumbs during the breeding season and summer.
  • Males have internal vocal sacs that located between the tympanum and the foreleg (Klemens 1993).
  • In general, secondary sexual characteristic are not typically evident outside of the breeding season; therefore, pickerel frogs can be rather difficult to sex (Wright and Wright 1949).

  • Voice: The call resembles the sound of tearing cloth. The prolonged note is distinctive and pitch varies with individual frogs but is always low (Dickerson 1906).
 
SIZE
AGE / SEX
SVL (SNOUT-VENT LENGTH) (cm)
SAMPLE SIZE
AVERAGE
RANGE
Std. Deviation
ADULT FEMALE
6.5
 5.5- 7.2
0.4
33
ADULT MALE
5.0
 4.0- 5.8
0.4
77
JUVENILE
3.9
 2.7- 5.0
0.5
63
METAMORPH
2.6
 1.9- 3.7
0.3
806


AGE / SEX
MASS (g)
SAMPLE SIZE
AVERAGE
RANGE
Std. Deviation
ADULT FEMALE
27.5
 19.7- 45.7
6.4
33
ADULT MALE
12.1
 6.2- 17.6
2.5
77
JUVENILE
5.5
 3.0- 9.9
2.0
63
METAMORPH
1.5
 0.5- 3.7
0.5
806




measurement data


 
RELATIVE ABUNDANCE
Rhode Island
Pickerel frogs are common in Rhode Island, although their populations appear to be localized. During surveys we conducted in ponds west of the Narragansett Bay, evidence of pickerel frogs breeding was somewhat uncommon- we detected eggs or tadpoles in only 6.7% of 119 ponds (Paton and Egan 2001). However, adults and juveniles were more frequently observed in the ponds and on the surrounding wetlands and streams (C. Heinz, pers. obser.)
Regional
Pickerel frogs are locally common throughout New England (Degraaf and Yamasaki 2001). Klemens (1993) found that only the green frog (Rana clamitans) is more widespread and abundant.
 
DISTRIBUTION
Rhode Island
Pickerel frogs are widespread throughout mainland Rhode Island (Raithel unpubl. data). In a 2000 survey of ponds, adults and larvae were detected in rural as well as urban areas of Rhode Island (Paton and Egan 2001); indicating this species is less affected by suburban and urban development.
Regional
Klemen (1993) reported pickerel frogs to be primarily a mainland species in the region. He found pickerel frogs to be widespread from sea level to over 1,700 feet (518 meters).
General
The pickerel frog is found throughout eastern North America. They range from southern Canada to South Carolina, westward to Texas and north to Wisconsin (Green and Pauley 1987). They are absent from most of the Gulf Coast and Florida, central Illinois, and northwest Ohio (Klemens 1993).
 
HABITAT NON BREEDING
Pickerel frogs tend to disperse from breeding sites after breeding and wander to adjacent wetlands and uplands. They often move into fields, meadows, and damp woods (Conant and Collins 1991; Mairs 1999). They prefer damp, cool, wooded areas with seeps, streams, or springs.

During the winter, pickerel frogs hibernate in the mud of pond bottoms, or in ravines or springs under rocks and other debris (Degaaf and Rudis 1983). Several authors report the presence of pickerel frogs overwintering in limestone caves. Johnson (1977) found pickerel frogs congregating in large groups in caves in Missouri and Resetarits and Aldridge (1988) reported similar observations.

 
HABITAT BREEDING
Pickerel frogs generally prefer cool, clear water found in such habitats as sphagnum bogs, rocky ravines, and meadow streams (Conant and Collins 1991), but this widespread species has been observed in various types of habitats, both disturbed and pristine (Klemens 1983; Paton and Egan 2001). Klemens (1993) collected pickerel frogs in Connecticut in wet meadows, the margins of lakes, ponds and reservoirs, marshes, fens, bogs, vernal pools, springs, shrubs and red maple swamps, sand pit and quarry ponds and along floodplains. They breed in both temporary ponds and permanent ponds but appear to favor ponds with long to permanent hydroperiods (Paton and Egan 2001). In Rhode Island, we found pickerel frog tadpoles and eggmasses in permanent manmade rural ponds, farm ponds, and urban ponds surrounded by roads; all of the mentioned habitats were well-vegetated (Paton and Egan 2001).
 
HYDROLOGY
In a survey of ponds in Rhode Island during the 2000 breeding season, we found pickerel frogs breeding only in ponds with long and permanent hydroperiods (Paton and Egan 2001). However, we found adults and juveniles using ponds of various hydroperiods.

hydrology data
 
MOVEMENT CHRONOLOGY
Adult pickerel frogs typically migrate to breeding ponds between mid April and early May (Paton and Crouch In press).

Metamorphs begin to emerge from breeding ponds in late July with the majority of the animals emigrating by late August (Paton and Crouch In press).

movement data

 

 
REPRODUCTION
In Rhode Island, pickerel frogs typically emerge from hibernation during mid April with the majority of the animals arriving at breeding ponds by early May (Paton and Crouch In press). At the ponds, pickerel frogs are gregarious as they are frequently observed in large groups in the water (Green and Pauley 1987). Mating behavior is not much different from other ranids. The males initiate breeding by emitting their low pitched call; a call so low pitched that it is not commonly heard during calling surveys (Crouch 1999). In addition, their calls are often difficult to hear in Rhode Island because they call at the same time as spring peepers (Pseudacris crucifer), which tend to drown out the quieter calls of pickerel frogs (P. Paton, pers. obs.). Males are known to call while submerged (Dickerson 1906). Amplexus can last a few days, even after the female has deposited the eggs (Mairs 1999).
 
EGG MASS
Egg masses are typically laid in well-vegetated areas and therefore they can be hard to find. The masses superficially resemble those of wood frogs but at close inspection one can usually distinguish between the two. Pickerel frog egg masses are spherical and about the same size of a wood frog eggmass- about 5-10 cm in diameter (Mairs 1999). The masses contains approximately 2000-3000 eggs (Wright and Wright 1949), in contrast to ca. 750 eggs in wood frog egg masses. In addition, the individual eggs of pickerel frogs are brown above and cream colored below, whereas wood frog eggs are black above. The mass is attached to woody or herbaceous vegetation near the surface of the water or to the depth of about 4 feet (Wright and Wright 1949). Development is temperature dependent but eggs typically hatch in 11 to 21 days (Degraaf and Rudis 1983). pickerel frog egg mass

 
LARVAE
Small pickerel frog tadpoles are yellowish to yellowish brown in color. As they grow, they become more olive green (Klemens 1993) to gray-brown above and creamy white below (Dickerson 1906). Larger tadpole are easily mistaken as green frogs (Dickerson 1906). However, there are a few characteristic to aid in distinguishing the two species. The nose of the pickerel frog tadpole is more pointed, the eyes are closer together, and the nostrils are closer to the edge of the nose (Dickerson 1906). Unfortunately these traits are difficult to assess especially if only one species is available for observation. The tadpole stage lasts about 3 months (Mairs 1999). pickerel frog tadpole
Pickerel frog tadpole

 
METAMORPHS
Metamorphs are small (see SIZE) but nearly as agile as the adult and juvenile when they emerge from the ponds (Dickerson 1906). In Rhode Island, they could only be mistaken for the closely related leopard frog (Rana pipiens). The dorsal ground color of the pickerel frog is a brassy-brown color; whereas, the leopard frog is more green to greenish-brown. pickerel frog metamorphing
Pickerel frog metamorphing

 
JUVENILES
Sexual maturity: pickerel frogs take 3 years to mature (Green and Pauley 1987).
 
FOOD
Adults
Adult pickerel frogs feed on mostly on land (Dickerson 1906) where they eat a wide array of invertebrate including: beetles, caterpillars, true bugs, ants, spiders, harvestmen, sowbugs, and mites (Mairs 1999). While in the water, they feed on snails, isopods, amphibians, and crayfish (Dickerson 1906).
Larvae
 
PREDATION
Adults
Pickerel frogs are toxic and are distasteful to numerous common amphibian consumers. Babbit (1937) reported that certain snakes (Nerodia and Thamnophis) avoided pickerel frogs, but researchers have since found remains of pickerel frogs in the stomach of Nerodia sipedon, Thamnophis sauritus, and Thamnophis sirtalis (Klemens 1993). Babbit (1937) also reported that bullfrogs (Rana catesbeiana) and green frogs (Rana clamitans) prey on pickerel frogs.
Larvae
{Predation Larvae/Tadpoles}
 
CONSERVATION CONCERNS
Pickerel frogs are currently widespread and secure in the region (Klemens 1993).
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