spring peeper Spring Peeper
Pseudacris c. crucifer
 
INTRODUCTION

In Rhode Island, spring peepers are often referred to as the "harbinger of spring" (Klemens 1993) because they generally start calling around the vernal equinox. They are one of the most prevalent frogs in the state, though the smallest (~1 inch long) that resides in southern New England. They make up for their diminutive size by emitting a high-pitched, loud, piercing call. Therefore it is their chorus that make them so apparent. Most people in Rhode Island have heard the loud vocalizations of peepers on a warm spring night in April; yet, few have ever seen a peeper because they are highly cryptic. Their body is camouflaged to resemble tree bark, where they commonly perch. In addition, they are secretive when approached, as they often remain perfectly still to avoid detection.

Males, the only ones to vocalize, produce two primary calls by expanding their throat pouch. While at breeding ponds, they emit a single, high-pitched note (i.e., resembling the call of a bird) that they repeat 15-25 times per minute. This call note is so high pitched that people often mistake this vocalization for an insect chirp and has also been likened to the ring of sleigh bells (Klemens 1993). This vocalization is intended to entice females to breeding ponds and select a particular male. (Davis 1999a). Males also utter a rapid trill when another male approaches too closely, that is apparently expressed in territorial disputes (Rosen and Lemon 1974).

 
IDENTIFICATION
  • Spring peepers are the smallest frog that lives in Rhode Island, most adults are only about 2-2.5 cm (one inch long) (see SIZE).
  • Adults are generally light brown, with a dark brown, variable "X" pattern on their dorsum. This dorsal pattern accounts for their species epithet, crucifer, which translates as "one who bears a cross". They are the only small, light brown frog in Rhode Island, with this marking on their on the back.
  • Their skin color is dynamic and often lightens at night; peepers can change skin color to resemble their background (Kats and VanDragt 1986).
  • The eyes, which are relatively small and brown, typically have a dark patch around them.
  • Each toe has a flattened, terminal pad. These pads are also present (and more prominent) on gray treefrogs. The terminal pads aid in vertical climbing abilities by adding surface tension through mucous secretions; the secretions increases adhesive capabilities (Duellman and Trueb 1986).
  • Hind feet are webbed.
  • The digits of the front limbs are relatively long.
spring peeper
spring peeper climbing

 

Sexual dimorphisms

  • Males have a dark, olive-brown vocal sac that appears as wrinkles on their throats (this allows the skin to expand when calling). The sac is most prominent during the breeding season (Oplinger 1966).
  • The ventral skin (throat and belly) of females is uniformly colored usually a yellowish-beige.
  • Females tend to be larger than males (see SIZE).
peeper ventral view male
male spring peeper (above)
female (at right)
peeper ventral view female
 
SIZE
AGE / SEX SVL (SNOUT VENT LENGTH) (cm) SAMPLE SIZE

AVERAGE

RANGE

ADULT FEMALE

2.8

1.9 - 3.5

498

ADULT MALE

2.5

1.8 - 3.2

596

JUVENILE

NA

NA

NA

METAMORPH

1.35

1.0 - 2.0

121



AGE/ SEX
MASS (g)
SAMPLE SIZE

AVERAGE

RANGE

ADULT FEMALE

1.8

0.4 - 3.0

498

ADULT MALE

1.2

0.3 - 2.2

596

JUVENILE

NA

NA

NA

METAMORPH

0.2

0.1 - 0.4

121




size data graph

 
RELATIVE ABUNDANCE
Rhode Island
Based on their loud choruses heard during April, peepers are one of the most abundant frogs in Rhode Island. Choruses can be detected from one-half mile away, and it could be assumed that these sites hold as many as a few thousand frogs. However, based on our research in Rhode Island at selected breeding ponds, we found that most ponds have hundreds, rather than thousands of peepers. For example, Paton et al. (2000) detected 192 males and 148 females immigrating to a 0.16 hectare breeding pond on Trustom Pond National Wildlife Refuge. At other similar sized ponds in Rhode Island, we have experienced similar capture rates (P. Paton, unpubl. data).
Regional
Abundant throughout the region, probably one of the most abundant frogs in southern New England (Klemens 1993; DeGraaf and Yamasaki 2001).
 
DISTRIBUTION
Rhode Island
Found throughout the state. We detected spring peepers in 50% of 119 ponds we sampled in Rhode Island west of Narragansett Bay during the 2000 field season (Paton and Egan 2001). Peepers on also common on Block Island (C. Heinz pers. obs.). They are found across the urbanization gradient, in Providence and Warwick, to the rural western part of the state.
Regional
Found throughout all states in New England. Burne (2000) detected spring peepers at 64% of 78 ponds around the Concord, Massachusetts area. Klemens (1993) collected peepers from sea level barrier beach ponds to mountaintop lakes as high as 610m (2000 feet) in the Berkshire mountains of western Massachusetts.
General
There are two subspecies of spring peepers. Northern Spring peepers (P. c. crucifer) are found throughout most of eastern United States, and much of Canada as far west as Manitoba (Klemens 1993). The northern terminus of their range extends from the Gaspe Peninsula westward through James Bay to Lake Winnipeg at about 50° N. latitude (Conant and Collins 1991). The southern spring peeper (P. c. bartramiana) is found only in northern Florida and southeastern Georgia.
 
HABITAT NON BREEDING

Peepers are habitat generalists, ranging from mature forests to old field habitats, although they are most commonly found in or near moist deciduous woodlands. They also can be found in coniferous forests, grassy meadows, shrubby fields, gardens, sandy coastal dune habitats, as well as pine barrens (Klemens 1993). In Rhode Island, we have even seen them at the southern tip of Sachuest Point National Wildlife Refuge, where the nearest forested patch was several kilometers away (P. Paton, pers. obs.).

Spring peepers in Rhode Island are found at breeding ponds from mid-March through May in Rhode Island (Paton et al. 2000, Paton and Crouch In press). The rest of year they reside away from breeding ponds where little is known about their ecology. They have been detected as far as 300 m (1,000 ft) from breeding ponds, however much more needs to be learned about dispersal distances of this secretive species (Davis 1999). Once peepers arrive on their non-breeding areas, they apparently establish territories (1-5 m [4-18 ft] diameter), generally around woody vegetation (bark debris, logs, stumps) (Delzell 1958)

peeper camouflaged
Spring peeper -camouflaged

During cold winter months, they hibernate, presumably under moss or leaf litter or in shallow burrows in the soil (Davis 1999b, DeGraaf and Rudis 1983). They are able to withstand freezing of body fluids for up to two weeks (Storey and Storey 1986).

 
HABITAT BREEDING
Spring peepers use a broad array of aquatic habitat for breeding site; however, they appear to prefer water bodies with relatively long hydroperiods (Paton and Egan 2001). Wright (1914) characterized their breeding habitat as any pool, ditch, or pond that had enough surface water to support successful breeding. Klemens (1993) reported peepers using woodland vernal pools, sphagnum bogs, red maple swamps, shrub swamps, swamps and marshes fringing lakes and reservoirs, wet meadows, fens, pasture ponds, bogs, quarry and sand pit ponds, brackish water lagoons behind barrier beaches, water filled ruts on dirt roads, and in flooded pastures. Peepers also breed in beaver ponds (Lykens and Forester 1987) and along the river floodplain, where they congregate in shallow, densely vegetated areas (C. Raithel, pers. comm.). Several authors suggest they prefer aquatic sites near brushy second-growth habitat (Conant 1975; Conant and Collins 1998). Conant and Collins (1998) also felt they preferred breeding ponds where trees or shrubs stand in the water. This is probably because males tend to form choral groups and vocalize from vegetation above the pond surface. Breeding ponds often have an open canopy, and extensive grass or emergent vegetation at pond edges (Murphy 1963).
 
HYDROLOGY
During our pond research in Rhode Island in 2000, spring peepers were detected in ponds with a variety of hydroperiods, although they tended to prefer ponds with longer hydroperiods( Paton and Egan 2001).

hydrology graph
 
MOVEMENT CHRONOLOGY

In Rhode Island, there are two times during the year when peepers are evident. March-May during the breeding season, when they are migrating to breeding ponds and during the fall (September-October) when you often hear single individuals calling from trees or bushes.

As with all other pond-breeding amphibians, peak movements take place rainy nights. In Rhode Island, adults are typically most active from 25 March to 27 May (Paton and Crouch In press). During this period, we captured 95% of adults immigrating towards breeding ponds in Rhode Island (Paton and Crouch In press). Lykens and Forester (1986) documented a similar pattern, with females arriving at breeding ponds over a 5-8 week period. Most breeding activity takes place during April, although based on captures of gravid females in May (Paton, unpubl. data) it is probable that some late females breed in ponds during May. Delzell (1958) suggested that female peepers mated quickly and left the pond within 1-2 days. After the end of May, it is very unusual to capture adults near breeding ponds, or even 125 m from breeding in forested areas (P. Paton, unpubl. data). We did not capture any adult peepers near breeding ponds in the fall, in contrast to other species such as wood frogs (Rana sylvatica)(Paton and Crouch, In press).

Metamorphs first start to emerge from breeding ponds at the end of June (~27 June). Peak emigration for metamorphs occurs around 22 July, with some individuals leaving ponds as late as 10 August (Paton and Crouch In press)

movement graph

 

 
REPRODUCTION

At breeding sites, males establish calling territories (Forester and Lykens 1986; Fellers 1979b) spaced about 0.5 m apart (Gerhardt et al. 1989)and occupy them for about a month (Delzell 1958). They tend to call from the ground on cold nights and from shrub or tree perches on warmer nights. Calling typically begins around dusk, with chorus volumes increasing throughout the evening; choruses can also be heard on warm afternoons. Wells and Bevier (1997) recorded peepers in Connecticut calling in air temperatures between 5-22°C and in water temperature from 10-20°C. Interestingly, there is sexual dimorphism in the hearing abilities of peepers. Studies show that females are more attuned to the frequency emitted by calling males, whereas males have difficulty hearing their own calls (Wilczynski et al. 1984). Perhaps males are just deaf from sitting in the midst of a huge chorus.

Once a pair is in amplexus, the pair will dive to the pond bottom to deposit eggs. In contrast to many anurans that oviposit eggs in communal aggregations, peepers deposit eggs singly under leaf litter or debris at the bottom of the pond (Klemens 1993). Therefore, detecting peeper eggs is extremely difficult.

 
EGG MASS
Peeper eggs are deposited singly on the pond bottom under vegetation and debris (e.g., leaf litter). Egg are small (~1.1 mm(0.04") in diameter)(Duellman and Trueb 1986) and therefore are difficult to detect. Eggs, which range in color from white to black (Wright and Wright 1949), hatch in <1 week if water is warm. Females may deposit as many as 900 eggs (Duellman and Trueb 1986).
 
LARVAE

Spring peepers remain tadpoles for about 90-100 days (Wright 1914). They reach a length of about 3 cm (1.2") before transforming (Dickerson 1906; Wright and Wright 1949). Their tail is 1.4-2.1 times their body length. Their ventral surface is reddish bronze and shiny with metallic luster. (Dickerson 1906). The eyes of the tadpoles are lateral; the only other tadpole in the state with lateral eyes is the gray treefrog (Hyla versicolor).

Spring peeper larvae tend to congregate in the warm shallows of ponds, in areas with dense vegetation where they are usually "inactive and benetic" - a stategy used as an anti-predator defense (Lawler 1989).

peeper tadpole
spring peeper tadpole

 

 
METAMORPHS

When metamorphs emerge from breeding sites, they resemble the adults but are smaller (see SIZE) and typically lighter in color.
peeper metamorph
 
JUVENILES

In contrast to most other anurans, we have never captured individuals that were intermediate in size between metamorphs and adults; that is, juveniles; therefore, they must grow rapidly during their first fall out of the breeding ponds

Sexual maturity: Delzell (1958) and Collins (1975) reported that both sexes of peepers breed in their first year of life.

 
FOOD
Adults

Adult peepers feed on a variety of small invertebrates, and thus, are beneficial to the environment by acting as natural pest control agents. Spiders account for the bulk of their diet (48%), although they also gorge themselves on mites, sowbugs, leafhoppers, ants, harvestmen, nematode worms, and lepidoptera (moth and butterfly) larvae (Gilhen 1984). In the spring, adults are known to eat their castoff skin (Duellman and Trueb 1986).

Recently emerged metamorphs apparently feed on spiders, ants, beetles, mites, ticks, caterpillars, and gastropods (Oplinger 1967); a diet similar to the adults.

Larvae
Larva feed on small aquatic organisms such as diatoms and algae attached to underwater vegetation (Oplinger 1967).
 
PREDATION
Adults
Because they are so small, adults are vulnerable to carnivorous insects, with giant water bugs and Dytiscid diving beetles documented preying on adults (Hinshaw and Sullivan 1990).
Larvae
The small tadpoles fall prey to aquatic predators such as fish, other frogs, newts, salamanders, and large carnivorous insects (Davis 1999a). As a defense mechanism, they move in large numbers at night is to avoid diurnal predators such as birds and snakes. In general, spring peeper larvae are relatively slow-growing, inactive, and poor competitors, so survival is often low (Morin 1995).
 
CONSERVATION CONCERNS

This species presently is secure in Rhode Island. It is widely distributed across the state, including urban areas. Peepers tend to be habitat generalist, as they are found in a variety of wetlands. Gibbs (1998b) investigated the effects of habitat fragmentation on five species of amphibians and found that peepers were among the least sensitive to habitat perturbations. However, they will not breed under all conditions. Glooschenko et al. (1992) found they were sensitive to acid rain, and larva are not found in ponds with a low pH (<4.0)(Freda and Taylor 1992). In contrast, Pierce (1985) found no evidence that peeper larvae were particularly sensitive to low pH. Pesticides may impact local populations, as one population had detectable levels of DDT 26 years after the last time it has been used in the area to control mosquito populations (Russell et al. 1995).

Although they typically prefer ponds with long hydroperiods, they tend to avoid ponds with fish (Hecnar 1997), therefore fish introductions to ponds could be detrimental to local populations. However, other researchers have found that peepers can avoid vertebrate predators hiding by quietly on the bottom of the pond (Lawler 1989; Smith and Van Buskirk 1995; Skelly 1995).

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