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47 At the end of the nineteenth century, there were indications that northern cricket frogs (Acris crepitans) were numerous in the midwestern United States. Garman (1892) found the species was “one of the most abundant members of the family in all parts of Illinois,” and Hay (1892) similarly indicated it was “one of our commonest batrachians” in Indiana. This abundance continued well past the middle of the twentieth century in both of these states (Smith, 1961; Minton, 1972). Campbell (1977) published the first report of a cricket frog decline in the relatively small area occupied by the species in extreme southern Ontario, Canada. This was puzzling because at least part of the area was protected as the Point Pelee National Park. Subsequently, Vogt (1981) reported a sharp cricket frog decline in Wisconsin, and 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; Moriarty, 1998); Wisconsin ( Jung, 1993; Casper, 1996, 1998; Hay, 1998a,b; Mossman et al., 1998); Colorado (H. Smith, personal communication; Hammerson and Livo, 1999); Ohio (Lipps, 2000); and Canada (Oldham, 1990, 1992; Weller and Green, 1997). Despite numerous reports of decline and ample scientific literature on the biology of cricket frogs, there is no clear-cut indication of the cause(s) of this trend toward extinction. However, a number of anthropogenic factors and environmental conditions have been suggested. Interestingly, as northern cricket frogs have become extinct in a number of peripheral areas, populations remain stable in the more central regions of the species range. Unlike the more celebrated frog declines, this is not a post-mortem case, and cricket frog declines thus present an excellent opportunity to study the process of amphibian extinction. Furthermore, amphibian declines are of obvious significance to the future of humankind (Wake, 1991; K. Phillips, 1994). Consequently, the objective of this contribution is to review the relevant biology and trend toward extinction of this widely distributed species. Morphological Characteristics Because northern cricket frogs may become extinct, we provide the following in-depth morphological description. Maximum reported snout-vent length is 38 mm (Conant and Collins, 1991), with males smaller (on average) than females. Skin on the dorsum, including the head, is rough with warts and ridges. The venter is granular. The snout is pointed and the male has a single subgular vocal sac. The hind legs are long, as are the hind toes, which have extensive webbing. There are two metatarsal tubercles and a tarsal fold on each hind limb. Toe pads are small. There are two relatively large palmar tubercles, with one at the base of the thumb and the other being adjacent. A fold occurs across the chest between the axillae. There is a pair of white tubercles (round, elongated, or of irregular shape) below the cloacal opening. The dorsal background coloration is typically black, brown, tan, olive green, or gray, although Gray (1995) reported some individuals to be entirely bright green dorsally. A vertebral stripe shows color polymorphism (red, green, and gray). Small green spots sometimes occur on other areas of the dorsum. Between the eyes is a dark triangular spot with the apex pointing posteriorly. On each side of the body is a dark stripe that is sometimes broken into spots. A dark stripe with irregular edges occurs on the posterior surface of the thigh; this stripe is sometimes broken into elongated spots. A white stripe extends between the base of the forelimb and the eye (this is often not clearly evident in preserved specimens). The limbs have dark bars (or spots) dorsally. The upper jaw has narrow light and wide dark bars. The pattern sometimes appears spotted or reticulated. The venter is white or cream with small dark flecks in the gular region. The male vocal sac is yellow with dark flecks. A detailed description of cricket frog eggs was given by Livezey (1950). The vitelli average 1.13 mm in diameter and are surrounded by two gelatinous envelopes. Up to 400 eggs are deposited singly or in small clumps of 2–7 eggs. Eggs float on the surface of the water, are...

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