Pseudacris crucifer (Wied-Neuwid, 1838)
Brian P. Butterfield1
Michael J. Lannoo2
1. Historical versus Current Distribution. In the United States, spring peepers (Pseudacris crucifer) are distributed throughout much of the east, reflecting the historical extent of the eastern deciduous and mixed forests. They occur east of a line from eastern Texas, north through extreme eastern Oklahoma and Kansas, though northwestern Missouri, eastern Iowa, and eastern and northern Minnesota (e.g., Wright and Wright, 1949; Conant and Collins, 1991). Spring peepers generally are found in most eastern wooded habitats, but are not found in the southern half of the Florida Peninsula. Two subspecies are recognized: northern spring peepers (P. c. crucifer), distributed throughout much of the species' range, and southern spring peepers (P. c. bartramiana), present in southeastern Georgia and northern Florida (Conant and Collins, 1991). The current distribution of spring peepers likely resembles their historical distribution, however populations have undoubtedly been lost with logging, the conversion from forest to agricultural land use, mining activities, road building, urbanization, and suburbanization.
2. Historical versus Current Abundance. Spring peepers are moderately common and occasionally abundant during the breeding season; they are difficult to collect in numbers during summer and fall (Wright and Wright, 1949). Spring peepers are one of the most ubiquitous and abundant frogs of the northern 40% of the Florida Peninsula and the eastern half of the panhandle (Bartlett and Bartlett, 1999a). At Portage Lake, Washtenaw County, Michigan, surveys in March, April, and May found that spring peepers were the most abundant animals (Carpenter and Delzell, 1951). These authors also note that 75% of the animals observed were road killed, illustrating the great potential automobiles have in causing mortality.
Blanchard (1928b) notes that spring peepers are found occasionally in bog forests in places that provide protection and breeding sites and are probably more common than they appear to be. In Lebanon County, Pennsylvania, Burger (1933) notes: "myriads" were heard and were taken along every stream and water body in the early spring, after which they are difficult to find. Welter and Carr (1939) note that spring peepers are "Very common throughout eastern Kentucky." For his studies on life history and food habits, Oplinger (1966, 1967) collected and sacrificed 1,322 spring peepers found in the marshes adjacent to Tomkins County Airport, near Ithaca, New York. Minton (2001) suggests that spring peeper numbers have been increasing in southwestern Indiana, but also notes that they are local and uncommon in former prairie areas and usually disappear from intensely cultivated areas.
3. Life History Features.
A. Breeding. Reproduction is aquatic. Spring peepers typically are among the first amphibians to emerge from hibernation, and for many people in the eastern and upper midwestern portions of the United States, their calling signals the arrival of spring.
i. Breeding migrations. From overwintering sites underground and in leaf litter to breeding ponds. Near Athens, Georgia, spring peepers breed in smaller, more open field ponds and pools rather than those on flood plains (Martof, 1955). In the southern United States, spring peepers begin to call on warm nights in December and January (Van Hymning, 1933; Voice, 1938; Wright and Wright, 1949). The breeding season occurs much earlier in Florida than in the north (Carr, 1940b; Wright and Wright, 1949). �Will breed when the temperature is [2 ˚C]. Ornate chorus frogs (Pseudacris ornata) are the only other Florida frog which breeds in such cold weather� (A. Carr, cited in Wright and Wright, 1949). Brandt (1936a) reported amplexed pairs in January in Beaufort County, North Carolina. Spring peepers are active on rainy winter nights when temperatures are above 10 ˚C (Ashton and Ashton, 1988; Bartlett and Bartlett, 1999a). In Charlton County, Georgia, the breeding season, as far as may be judged by vigorous choruses, extends from late November more or less continuously to early March (F. Harper, cited in Wright and Wright, 1949). Near Athens, Georgia, spring peepers begin calling in the second week of January (Martof, 1955). In eastern Kentucky, they are first heard in the second week in February (Welter and Carr, 1939). Near Indianapolis, Minton (2001) notes choruses during the first week in March during mild, rainy nights and that chorusing begins about 2 wk later in northern Indiana. He further notes that the breeding season extends into early May. In Kalamazoo County, Michigan, spring peepers were heard in full chorus in early April, choruses continued until early June (Allen, 1937). Allen observed the highest abundances "�in the shallow swales, among the dead grass and sedges. A few were heard in the marshy borders of the lake but they were not numerous here in comparison." Martof (1960) reported the occurrence of autumn (27 September) breeding in a spring peeper population near Athens, Georgia.
Call characteristics of spring peepers have been documented by Rosen and Lemon (1974), Forester and Lykens (1986), Etges (1987), Lykens and Forester (1987), Schwartz (1989), Sullivan and Hinshaw (1990), and Lance and Wells (1993). Spring peepers exhibit size-selective mating with larger males breeding more frequently (Gatz, 1981b).
ii. Breeding habitat. Males sing in buttonbrush, briars, willows, Decodon, etc. and emergent herbaceous vegetation at the water�s edge in small wooded ponds, larger swamps, vernal pools, flooded ditches, wet meadows, Carolina Bays, cypress heads, and sandy coastal and pine barrens habitats (Wright, 1914; A. Carr, cited in Wright and Wright, 1949; Smith, 1961; Mount, 1975; Vogt, 1981; Green and Pauley, 1987; Dundee and Rossman, 1989; Klemens, 1993; Oldfield and Moriarty, 1994; Hunter et al., 1999). Minton (2001) observes that suitable breeding ponds are near woods and are large and permanent enough to support emergent vegetation, but too shallow and temporary to contain fishes.
i. Egg deposition sites. Eggs are attached singly or in clumps to submerged vegetation in seasonal and semipermanent wetlands (e.g., Olson, 1956; Minton, 2001). Ovulation precedes amplexus (Oplinger, 1966).
ii. Clutch size. Loraine (1984) collected a female that had laid 702 eggs. Oplinger (1966) gives an average of > 700 eggs from females > 30 mm, with a maximum estimate of 1,000 eggs (Wright and Wright, 1949). Eggs hatch in 1�2 wk (Ashton and Ashton, 1988; 6�15 d, Minton, 2001). In southern spring peepers, eggs are laid singly, mean diameter is 1.1 mm (vitellus), 2.6 mm (jelly envelope). Eggs hatch in 5.5�6.5 d "at room temperature" (Gosner and Rossman, 1960).
C. Larvae/Metamorphosis. Southern spring peeper tadpoles average 8�10% larger than those of northern spring peepers (Gosner and Rossman, 1960). As is true for many hylids, spring peepers possess a melanophore covering within their peritoneum that forms a complete black lining of the coelom.
i. Length of larval stage. Tadpoles metamorphose in approximately 3 mo (Wright and Wright, 1949; Minton  states 90�100 d). In the laboratory, the minimum size to metamorphosis in southern spring peepers was 45 d, at a mean size of 10.3 mm SVL (Gosner and Rossman, 1960). In New Jersey, Gosner and Black (1957a) note the earliest they observed newly metamorphosed spring peepers was 30 May.
ii. Larval requirements.
a. Food. As is true of most North American anurans, spring peeper tadpoles are suspension feeders that graze on organic and inorganic material typically associated with submerged surfaces.
b. Cover. Tadpoles will aggregate. Brattstrom (1962b) documented several aggregations of spring peeper tadpoles, including one composed of about 75 individuals, in early May in Lake Panamoka, New York. However, laboratory observations using spatial affinity as a recognition assay did not demonstrate sibling recognition (Fishwald et al., 1990).
iii. Larval polymorphisms. Do not occur.
iv. Features of metamorphosis. At metamorphosis, spring peepers are from 12�14 mm TL. Mass migrations of post-metamorphic animals have not been recorded.
v. Post-metamorphic migrations. From wetlands to the forest floor and into low brush.
D. Juvenile Habitat. Similar to adults, although juveniles can be diel and will feed in adjacent grasslands or on the vegetation supported by sphagnum bogs (M.J.L., personal observations).
E. Adult Habitat. Adults are found in lowland marshes, wetlands at the sources of streams whether wooded or open, associated with sphagnum bogs and cattail wetlands, ponds, pools, and ditches in and near woods (Wright and Wright, 1949). Mesophytic and low hammock, swamp borders, the more open bay-heads, and tangles along the smaller streams. In Beaufort County, North Carolina, non-breeding adults retreat to woodlands to feed and for cover (Brandt, 1936a). In Indiana, Minton (2001) notes that the optimal habitat for spring peepers is moist, upland woods with shallow ponds. They avoid floodplain forest. In Connecticut, Gibbs (1998b) notes that populations of spring peepers are resistant to habitat fragmentation.
F. Home Range Size. Unknown.
G. Territories. Unknown but unlikely, except for calling males during the breeding season.
H. Aestivation/Avoiding Dessication. Spring peepers avoif dry and hot conditions by retreating under logs and bark and perhaps in knot-holes (Wright and Wright, 1949; see also Hudson, 1950). These frogs reach their critical activity point (cannot perform buccal movements in addition to other criteria) when they lose about 33% of their water in desiccating environments (Farrell and MacMahon, 1969). Farrell (1971) demonstrated that desiccation tolerance varies, perhaps due to seasonal physiological adjustments. Spring peepers exhibit a water absorption response (Stille, 1958).
I. Seasonal Migrations. Mass migrations do not occur. Instead, individuals are generally able to feed, breed, and overwinter within the vicinity of forested wetlands.
J. Torpor (Hibernation). Spring peepers hibernate under logs and bark and in knotholes�sites that are the same or similar to retreat sites used to avoiud hot, dry conditions (Wright and Wright, 1949; see also Hudson, 1950; and "Aestivation/Avoiding Dessication" above). They produce an antifreeze consisting of low molecular weight cryoprotectants (glucose, with a rise to 150�300 mM) that assist in limiting cell volume reduction of up to 65% of total body water as extracellular ice (Churchill and Storey, 1996). Spring peepers typically are among the first amphibians to emerge from hibernation, and animals that form early choruses show good freezing survival (Storey and Storey, 1987; Churchill and Storey, 1996).
In reporting on a population from Beaufort County, North Carolina, Brandt (1936a) notes that there is no evidence of a prolonged hibernation, and that animals are observed throughout the winter "at all temperatures above freezing."
K. Interspecific Associations/Exclusions. In Alachua County, Florida, spring peepers occupy essentially the same habitat as the much rarer eastern gray treefrogs (Hyla versicolor; A. Carr, cited in Wright and Wright, 1949). At a historical site near Bloomington, Indiana, spring peeper egg masses were found in association with egg masses of green frogs (Rana clamitans), leopard frogs (Rana pipiens complex), and gopher frogs (Rana areolata; Wright and Myers, 1927). In North Carolina, Schwartz (1955) noted spring peepers chorusing in association with mountain chorus frogs (Pseudacris brachyphona; see also Barbour and Walters, 1941), wood frogs (R. sylvatica), and spotted salamanders (Ambystoma maculatum). In April in Morgan County, Alabama, Cahn (1939) described a breeding wetland with spring peepers, American bullfrogs (R. catesbeiana), southern leopard frogs (R. sphenocephala), northern cricket frogs (Acris crepitans), southern cricket frogs (A. gryllus), eastern gray treefrogs, barking treefrogs (H. gratiosa), and Fowler's toads (Bufo fowleri). In west-central Wisconsin, spring peepers breed in association with wood frogs, western chorus frogs (P. triseriata), gray treefrogs, and American toads (B. americanus; M.J.L., personal observations).
Spring peeper and western chorus frog tadpoles often co-occur in ponds across the Upper Midwest (Skelly, 1996).
L. Age/Size at Reproductive Maturity. At 28 mm (Wright and Wright, 1949); 10�31 cm (Bartlett and Bartlett, 1999a). Oplinger (1966) noted that the smallest males with mature spermatozoa were 18 mm; the smallest females with eggs were 23 mm.
M. Longevity. One animal lived 2 yr, 2 mo, and 9 d following capture in the wild (Snider and Bowler, 1992).
N. Feeding Behavior. McAlister (1963) noted a post breeding, feeding assemblage of nearly adult spring peepers (numbering 37; 17.8�26.7 mm SVL) associated with two juvenile eastern gray treefrogs and two juvenile northern leopard frogs on the evening of 2 September 1962. All but one leopard frog were found on the upper branches of goldenrods (Solidago sp.), elderberries (Sambucus sp.), boneset (Eupatorium perfoliatum), and Joe-pye weed (E. purpureum). The frogs were feeding on insects attracted to the flowers. Gut contents of 25 spring peepers showed that they were feeding on small arthropods, spiders, phalangids, and mites (Tetranychidae).
Oplinger (1967) gives a detailed list of the food habits of 545 young-of-the-year spring peepers and makes several observations. He notes that food habits are based on prey availability rather than preference and that prey such as arachnids, ants (Hymenoptera), and beetles (Coleoptera) that are generally found throughout the year are eaten throughout the year. Slow-moving, crawling animals were preyed upon more often than active flying animals. No aquatic prey items were eaten. Some seeds, which when windborn could be mistaken for prey, were ingested. Oplinger (1967) did not find a correlation between the size of the spring peeper and the number of prey items in their stomach. Small peepers tended to feed on smaller prey. Feeding activity for younger animals peaked in the early morning and late afternoon; adults tended to feed during the day, from late afternoon to early evening.
O. Predators. Known predators include Butler's garter snakes (Thamnophis butleri; Test, 1958), giant water bugs (Belostomatids; Hinshaw and Sullivan, 1990), predaceous diving beetles (Coleoptera; Formanowicz and Brodie, 1982), and other pond invertebrates such as odonates (Skelly, 1996). Cochran and Cochran (2003) report spring peepers eaten by brown trout (Salmo trutta).
P. Anti-Predator Mechanisms. Spring peepers are small, inconspicuous, and considered to be strong jumpers (Zug, 1985), and as with most frogs, will use their jumping ability to escape prey (Inger, 1962; Gans and Parsons, 1966). Among the species studied by Zug (1985; including members in the following genera: Bufo, Acris, Pseudacris, Hyla, and Rana), spring peepers had the least degradation of performance in repeated jumps.
Q. Diseases. Unknown.
R. Parasites. The trematode Glypthelmins pennsylvaniensis has been reported in spring peepers from Pennsylvania (Cheng, 1961), Wisconsin (Coggins and Sajdak, 1982), Michigan (Muzzall and Peebles, 1991), and West Virginia (Joy and Dowell, 1994). Muzzall and Peebles (1991) reported the nematodes Cosmocercoides sp., Oswaldocruzia pipiens, Rhabdias ranae, and Spiroxys sp. in spring peepers from southern Michigan.
4. Conservation. Spring peepers are listed as Threatened in Kansas and Protected in New Jersey (Levell, 1997). These designations offer legal protection and require that permits be obtained before undertaking any activities involving this species.
Spring peepers are difficult to collect in numbers during summer and fall, making population assessments difficult. Minton (2001) suggests that spring peeper numbers have been increasing in southwestern Indiana, but also notes that in other parts of the state they usually disappear from areas of intense human activity.
1Brian P. Butterfield
Department of Biology
Henderson, Tennessee 38340-2399
2Michael J. Lannoo
Muncie Center for Medical Education
Indiana University School of Medicine
Ball State University
Muncie, Indiana 47306
USGS-Patuxent Wildlife Research Center
12100 Beech Forest Road
Laurel, Maryland 20708-4031
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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