Acris crepitans Baird, 1854(b)
Northern Cricket Frog
Robert H. Gray1
Lauren E. Brown2
1. Historical versus Current Distribution. The historical distribution of northern cricket frogs (Acris crepitans) is primarily across the eastern half of the United States (Conant and Collins, 1991, map 311). The extremities of the historical range extended from southeastern New York state, south to the eastern panhandle of Florida, west to western Texas and southeastern New Mexico, north to western Nebraska and southeastern South Dakota, and east across central Wisconsin and central Michigan. The species does not occur on the Atlantic Coastal Plain (except for relictual populations) from southeastern Alabama to southeastern Virginia, nor do they occur in the Appalachian Mountains from southwestern North Carolina northward, nor their foothills in eastern Ohio. Cricket frogs also occur in northern Coahuila, Mexico (not far from the U.S./Mexican border), and historically occurred in extreme southern Ontario, Canada (Point Pelee Peninsula and Pelee Island in Lake Erie; Oldham, 1992).
Three subspecies of northern cricket frogs are recognized: Blanchard's (A. c. blanchardi), eastern (A. c. crepitans), and coastal (A. c. paludicola). Blanchard's cricket frogs are represented in the West and Midwest; eastern cricket frogs are found in east Texas, the Gulf Coast and southern forest regions, and the Piedmont north to New York; coastal cricket frogs are found in the Gulf Coast region of western Louisiana and eastern Texas.
Severe declines of northern cricket frogs have been reported throughout the northern extent of their range (primarily Blanchard's cricket frogs), which have produced scattered and isolated populations. In addition to these declines, northern cricket frog populations are also scattered and isolated along the western and southeastern peripheries of their range. For example, there are a number of isolated records along the more arid western edge of their distribution (e.g., Nebraska [Lynch, 1985]; Colorado [Hammerson, 1986; Hammerson and Livo, 1999]; Texas [Milstead, 1960]; New Mexico [Degenhardt et al., 1996]; and Arizona [Frost, 1983]; see also Veldman, 1997). Furthermore, isolated populations have been also reported on the Atlantic Coastal Plain of the southeastern United States in North Carolina and South Carolina (Conant, 1975, 1977a).
2. Historical versus Current Abundance. At the end of the nineteenth century, there were indications that northern cricket frogs were numerous in the midwestern United States. Garman (1892) found that they were "one of the most abundant members of the family in all parts of Illinois," and Hay (1892) similarly indicated they were "one of our commonest batrachians" in Indiana. This abundance continued well past the mid twentieth century in both of these states (Smith, 1961; Minton, 1972). Campbell (1977) published the first report of a northern cricket frog decline in extreme southern Ontario, Canada—puzzling because at least part of the area was protected as the Point Pelee National Park. Vogt (1981) next reported a sharp northern cricket frog decline in Wisconsin, and subsequently numerous declines have been, and continue to be, reported throughout the upper midwest and elsewhere: Illinois (Mierzwa, 1989, 1998a; Ludwig et al., 1992; Greenwell et al., 1996); Indiana (Minton et al., 1982; Vial and Saylor, 1993; Brodman and Kilmurry, 1998; Minton, 1998); West Virginia (T. Pauley, personal communication); Iowa (Christiansen and Mabry, 1985; Lannoo et al., 1994; Lannoo, 1996, 1998a; Christiansen and Van Gorp, 1998; Hemesath, 1998); Michigan (Harding and Holman, 1992; Harding, 1997; Lee, 1998); Minnesota (Vial and Saylor, 1993; Oldfield and Moriarty, 1994; Moriarity, 1998); Wisconsin (Jung, 1993; Casper, 1996, 1998; Hay, 1998a,b; Mossman et al., 1998); Colorado (H. Smith, personal communication, 1998; Hammerson and Livo, 1999); Ohio (Lipps, 2000); and Canada (Oldham, 1990, 1992; Weller and Green, 1997). Despite numerous reports of declines, and ample scientific literature on the biology of northern cricket frogs, there is no clear-cut indication of the cause(s) of this trend toward extinction, although a number of anthropogenic factors and environmental conditions have been suggested.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Spring emergence for northern cricket frogs typically begins in early March in southern Illinois, late March or early April in central Illinois (Gray, 1983), and early April in central Iowa (Johnson and Christiansen, 1976). The male vocal pouch begins to develop in some northern cricket frogs in October, while in other individuals the vocal pouch is not apparent until April or early May. Male northern cricket frogs probably are the first to arrive at breeding sites (Pyburn, 1958; Gray, 1983). In Illinois, calling males are first heard in late April or early May and last heard in July (Gray, 1983) or early August (L.E.B., personal observations). In central Iowa, calling males are first heard in mid May and are last heard in late July (Johnson and Christiansen, 1976). The male mating call is a sharp “glick, glick, glick…” and resembles two glass marbles or small stones being struck together. The repetition rate of the “glicks” is faster in the middle of a call sequence than at the beginning or end. Males sit on the bank or on floating aquatic vegetation and call during the day and night.
The number and intensity of male choruses suggests that breeding activity peaks in May, when population sizes are declining. Females mobilize body lipids during ovarian development (Long, 1987a). Gravid females are identified by developing eggs—visible through the skin in the groin—and are present from late April to late August. In Illinois, females mature eggs once annually. The sex ratio of northern cricket frogs in Illinois favors males by about 3:1 and appears even higher at some locations (see Gray, 1984). Mate preference of female northern cricket frogs is influenced by three call characteristics: dominant frequency, number of pulses/call, and number of pulse groups/call (Ryan et al., 1995). Females attracted to calling males are clasped in axillary amplexus. Interestingly, some gravid females can be found after the last calling males are heard (Gray, 1983), suggesting that all females may not breed.
Northern cricket frog populations in the south differ from those in the north in several respects. Evidence suggests that northern cricket frogs in Texas and Louisiana are active year-round and probably experience two breeding peaks (Pyburn, 1961a; Bayless, 1966); southern cricket frogs (Acris gryllus) are also prolonged breeders (Forester and Daniel, 1986). Additionally, sex ratios of northern cricket frogs in the south approximate 1:1, and breeding population sizes are larger (Jameson, 1950a; Blair, 1961a).
ii. Breeding habitat. Semi-permanent and permanent wetlands and river backwaters.
i. Egg deposition sites. Eggs either float on the surface of the water, are scattered on the bottom, or are attached to stems of submergent vegetation.
ii. Clutch size. Up to 400 eggs are deposited singly or in small clumps of 2–7 eggs. A detailed description of northern cricket frog eggs is given in Livezey (1950). The vitelli average 1.13 mm in diameter and are surrounded by two gelatinous envelopes.
i. Length of larval stage. From 50–90 d or longer (Wright and Wright, 1949). Burkett (1984) noted the tadpole stage lasts 35–70 d (5–10 wk). Working in the laboratory, Pyburn (1956) noted a larval period from 29–90 d.
ii. Larval requirements.
a. Food. Cricket frog tadpoles feed on periphyton and phytoplankton (Johnson, 1991).
b. Cover. Tadpoles are secretive and seek shelter in aquatic vegetation when startled (L.E.B., personal observations).
iii. Larval polymorphisms. Tadpoles that co-occur with dragonfly (Anax sp.) larvae in ponds tend to have black tails, while tadpoles in lakes and creeks where fish predominate are mostly plain tailed (Caldwell, 1982a). This polychromatism may reflect differential selection by these predators.
iv. Features of metamorphosis. Metamorphosis begins in late July or early August and continues for about 3 wk.
v. Post-metamorphic migrations. Juvenile northern cricket frogs can disperse from breeding wetlands out perhaps 100 m to other aquatic sites (Gray and Brown, 2002).
D. Juvenile Habitat. Same as adults. Growth of newly metamorphosed frogs is rapid during the fall. Individuals can grow from 12–26 mm in 2–3 mo (Gray, 1983).
E. Adult Habitat. Northern cricket frogs are terrestrial and semiaquatic. Individuals potentially can occur in or near virtually any body of fresh water, although they tend to be rare or absent at large lakes, wide rivers, and polluted sites. Northern cricket frogs typically occupy a zone along the water’s edge, sitting on floating vegetation and debris or on exposed beach-like banks (e.g., Smith et al., 2003). When approached by a potential predator, northern cricket frogs make several quick zigzag leaps (each often 1 m or more in length) on the bank and/or floating vegetation. They then dive underneath the water or come to rest on the shoreline some distance away. Experimental studies show a progressive decline in locomotory performance over an extended period of consecutive jumps (Zug, 1985). Northern cricket frogs sometimes occur in cattail (Typha sp.) thickets as well as in other terrestrial and/or aquatic shoreline vegetational assemblages. Northern cricket frogs occasionally are heard calling on floating vegetation over deeper water a considerable distance from the edge of a pond. In some flood plain forests, northern cricket frogs are often encountered on damp soil and under logs some distance from aquatic sites. After rains, northern cricket frogs disperse to more distant aquatic sites (Gray, 1983; Burkett, 1984) and often pass through drier, suboptimal terrain.
F. Home Range Size. Adults generally remain near wetlands, but migrate between them. The subject of home ranges has not been determined.
G. Territories. Unknown but unlikely. During breeding , distance to the nearest neighbor appears to have the greatest influence on variation in male calling behavior, with the most profound changes occurring during aggressive encounters (Wagner, 1989a,b). Calls at the middle and end of a call sequence are modified in response to male–male aggressive interactions. The hormone arginine vasotoxin increases the probability of male calling and alters the middle and end of a call sequence of more aggressive males to that of less aggressive males (Marler et al., 1995). Males may signal information about their size and fighting ability through changes in call dominant frequency (Wagner, 1989a,c, 1992).
H. Aestivation/Avoiding Dessication. During a period of severe drought in Texas, W.F. Blair (1957) reported that northern cricket frogs avoided desiccation by taking refuge in deep cracks in the bed of a dry pond. Similar behavior has been observed in Indiana (L.B., personal observations).
I. Seasonal Migrations. Dispersal of northern cricket frogs from one population to another tends to occur after rains. Gray (1983) observed northern cricket frogs moving up to 1.3 km between farm ponds in central Illinois. Frogs that dispersed from one location and were later recaptured at another represented 1–7% of the original population. However, many more frogs likely dispersed and either reached other sites or died in transit.
J. Torpor (Hibernation). As temperatures decline in the fall, northern cricket frogs become less active and are usually last seen in late October in central Iowa (Johnson and Christiansen, 1976) or late November in central Illinois (Gray, 1971a). However, they may be active during the winter in some areas of Illinois, west-central Indiana, Kansas, Oklahoma, Texas, Louisiana, and elsewhere in the south on warm days or where there are springs (Blatchley, 1892; Pope, 1919; Linsdale, 1927; Jameson, 1950a; Blair, 1951b; Pyburn, 1956, 1961a; Gray, 1971a). Northern cricket frogs in central Illinois overwinter in cracks in the banks formed by freezing, drying, and subsequent contraction of the soil (Gray, 1971a; see Irwin et al., 1999; Irwin, this volume, Part One). Other workers have found them during the winter under logs, under a mass of compact dead vegetation, and buried in gravelly soil (Garman, 1892; Walker, 1946; Pope, 1964a; Irwin et al., 1999; Irwin, this volume, Part One). On warm winter days in southern Illinois, northern cricket frogs are sometimes active on ice (L.E.B., personal observations). Growth stops in winter, and individuals may actually be smaller when first observed in spring (Gray, 1983), possibly due to the overwinter metabolism of and subsequent reduction in body lipids and nonlipid material in the liver (Long, 1987a). Interestingly, most northern cricket frogs that survive to overwintering also survive to the spring emergence. Thus, overwintering is not a major cause of mortality in Illinois populations (Gray, 1983). McCallum and Trauth (2003) report communal hibernation on the Ozark Plateau.
K. Interspecific Associations/Exclusions.
Northern cricket frogs can be associated with green frogs (Rana clamitans; Jung, 1993; L.E.B., personal observations), northern leopard frogs (R. pipiens), wood frogs (R. sylvatica), American bullfrogs (R. catesbeiana), Fowler’s toads (B. fowleri), American toads (B. americanus), eastern gray treefrogs (Hyla versicolor), western chorus frogs (Pseudacris triseriata), spring peepers (P. crucifer; L.B. personal observations), and a great many other anuran species.
L. Age/Size at Reproductive Maturity.
Maximum reported length is 38 mm SVL (Conant and Collins, 1991), with males smaller on average than females.
Burkett (1984) states that northern cricket frogs have an average life expectancy of about 4 mo and a complete population turnover in 16 mo. Gray (1983) found marked animals that survived two winters. Using skeletochronology, S. Perrill (personal communication) has found 3-yr-old northern cricket frogs.
N. Feeding Behavior.
Northern cricket frogs are opportunistic and apparently feed both day and night (Johnson and Christiansen, 1976) on whatever small invertebrates are available on the ground or in the air. Food items include aquatic and terrestrial insects and spiders (Garman, 1892; Hartman, 1906; Jameson, 1947; Gehlbach and Collette, 1959; Labanick, 1976b), and occasionally annelids, mollusks, crustaceans, and plant matter (Hartman, 1906; Johnson and Christiansen, 1976). Food consumption is greater in larger frogs, female frogs, frogs that are reproducing, small frogs with fat bodies, and frogs collected in June and July (Johnson and Christiansen, 1976).
A drastic reduction in number of northern cricket frogs occurs from metamorphosis until breeding in Illinois (Gray, 1983) and Kansas (Burkett, 1984). In Illinois, this reduction ranges from 50–97%. Thus, in many populations of northern cricket frogs, numbers of potential breeding individuals are low. The critical period—when northern cricket frogs in Illinois are most susceptible to predation—is in the fall when water recedes and pond banks are exposed. Animals known or observed to prey on northern cricket frogs include American bullfrogs, fishes (e.g., bass, Micropterus sp.), common and plains garter snakes (Thamnophis sirtalis and T. radix), northern and Concho water snakes (Nerodia sipedon and N. paucimaculata), turtles (R.H.G., personal observations), kestrels (Falco sparverius), great-tailed grackles (Cassidix mexicanus), other birds, and mammals (Carpenter, 1952; Lewis, 1962; Fitch, 1965; Wendelken, 1968; Gray, 1978; Fleming et al., 1982; Greene et al., 1994). Adults from the previous year have usually disappeared by the end of October.
P. Anti-Predator Mechanisms.
Animals are cryptic, exhibit color polymorphism (Pyburn, 1956, 1961a,b; Wendelken, 1968; Gray, 1971b, 1972, 1977, 1995; Issacs, 1971; Jameson and Pequegnat, 1971; Nevo, 1973; Milstead et al., 1974), and have a remarkable ability to leap (to 1 m). Details of escape behavior have recently been described by Johnson (2003).
Gray (1995, 2000 a,b) documented morphological abnormalities and frequencies of abnormalities from northern cricket frog populations in Illinois (see also Beasley et al., this volume, Part One; L. B., personal observations).
Greenwell et al. (1996) found a massive amount of kidney parasitism in juvenile northern cricket frogs from Illinois (see also Beasley et al., this volume, Part One).
Northern cricket frogs are listed as Endangered in Minnesota and Wisconsin, Threatened in New York, and as a Species of Special Concern in Indiana, Michigan, and West Virginia (Brodman and Kilmurry, 1998; Ramus, 1998). In Canada, they are listed as Endangered in Ontario and on the national level (Weller and Green, 1997). Interestingly, as northern cricket frogs are becoming extirpated in a number of peripheral areas, populations remain stable in the more central regions of their range. Absence of listings in other U.S. states where declines have been noted may reflect the current abundance of northern cricket frogs in the southern parts of those states or a lassitude and/or impenetrability of the state’s endangered species bureaucracy. While causes of northern cricket frog declines remain elusive, in experimental studies, northern cricket frog tadpole abundance was reduced in acidified macrocosms compared with circumneutral ones and reduced in macrocosms with loam soils compared with clay soils (Sparling et al., 1995). Contaminants in waters inhabited by northern cricket frog tadpoles may be accumulated in tissues, causing not only acute and chronic effects (Boschulte, 1995; Greenwell et al., 1996), but also effects that may also be passed to higher trophic levels through predation (Hall and Swineford, 1981; Fleming et al., 1982; Sparling and Lowe, 1996).