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292 During the 1970s, John D. Lynch and his students conducted extensive fieldwork in Nebraska to complete a herpetological survey begun by George E. Hudson nearly three decades earlier (Hudson, 1942; Lynch, 1985). In the wake of alarm calls concerning the status of amphibians around the globe since the late 1980s and early 1990s numerous studies have been conducted to determine whether or not amphibians are in fact declining and if changes are the results of local or global phenomena. During the late 1990s, I revisited the work done by Lynch to address questions of amphibian population declines at the state level in Nebraska since the 1970s. During his survey, Lynch employed larval sampling techniques as a means of rapidly acquiring distributional data on amphibian populations in the state. The absence of terrestrialbreeding amphibians made larval sampling an effective methodology for sampling all 13 species of amphibians found within the state. In Nebraska, the amphibian breeding season begins in April and typically extends through August (Hudson, 1942; Billings, 1973; Lynch, 1985). A window of opportunity exists for approximately 6 weeks during the early summer in which all species that have bred will have larvae in ponds across the state; thus, those species can be sampled simultaneously. In 1997 and 1998 I resurveyed Nebraska amphibian populations and compared these data to Lynch’s 1970s’ data (presumably pre-decline) to determine the status of this state’s amphibians (McLeod, 1999). I revisited Lynch’s original sites, repeated his methodologies, and added new and replacement sites as needed to determine whether changes had occurred during the intervening 20 years. Because changes had occurred, I addressed the following questions: (1) Had all species of amphibians been affected? (2) Were changes regional or statewide? (3) What possible causes may explain these changes? Over a two-year period (3 June to 9 July 1997 and 1 June to 10 July 1998) I visited 267 sites, of which 181 were original sites sampled by Lynch. Ninety-six of Lynch’s original sites were located and sampled. Eighty-five of the original sites were unavailable for sampling due to land-use changes or disappearance; these were replaced with nearby ponds selected on the basis of ecological characteristics given in Lynch’s original field notes and distance from the original site. Thirty-nine original sites visited were abandoned because they were neither available for sampling nor able to be replaced appropriately. Forty-six new sites were added to the study. I replicated Lynch’s methodology of collecting presence/absence data by sampling larvae with a one-man push seine and/or a fine mesh dip net. Larvae were identified, recorded, and released. I made general notes on amphibian relative abundance and appearance, as well as on pond characteristics. Current land owners were interviewed and pond history obtained whenever possible. Eleven species of amphibians commonly occur in the state of Nebraska (Lynch, 1985): northern cricket frogs (Acris crepitans ), small-mouthed salamanders (Ambystoma texanum), eastern tiger salamanders (A. t. tigrinum), Great Plains toads (Bufo cognatus), Woodhouse’s toads (B. woodhousii), Cope’s gray treefrogs (Hyla chrysoscelis), western chorus frogs (Pseudacris triseriata), plains leopard frogs (Rana blairi), American bullfrogs (R. catesbeiana), northern leopard frogs (R. pipiens), and plains spadefoot toads (Spea bombifrons). Two other historically present species, American toads (B. americanus) and western narrow -mouthed toads (Gastrophryne olivacea) were not collected during either study and are consequently not included in this study. Lynch found larvae at all (100%) of his 269 sites. During my survey, I found 40.9% of 227 ponds sampled to be unoccupied (McLeod, 1999). Seven of 11 species exhibited significant declines in occurrence at the state level (Table 42-1). Species that declined included northern cricket frogs, eastern tiger salamanders , Woodhouse’s toads, western chorus frogs, plains leopard frogs, northern leopard frogs, and plains spadefoot toads. Of the four remaining species, Cope’s gray treefrogs increased significantly in occurrence, but they were collected only in the 1998 field season (McLeod, 1999). To determine if amphibian declines represented regional or statewide phenomena, presence/absence data were sorted into four, independently designated ecological areas based on zones of native vegetation (Kaul and Rolfsmeier, 1993). Collection values for each species were compared between decades and across pond types within each zone. The number of amphibian species known to occur in each zone are: (1) eleven species occur in upland tall grass prairie (Zone 1), which comprises the eastern third of the state; (2) seven species in loess and mixed grass prairie...

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