Arizona distribution of three Sonoran Desert anurans: Bufo retiformis, Gastrophryne olivacea, and Pternohyla fodiens

Great Basin Naturalist 56(1), © 1996, pp. 38-47 ARIZONA DISTRIBUTION OF THREE SONORAN DESERT ANURANS: BUFO RETIFORMIS, GASTROPHRYNE OLIVACEA, AND PTERNOHYLA FODIENS Brian K. Sullivan 1, Robert W. Bowker^, Keith B. Malmos^, and Erik W. A. Gergus'^ Abstract. — We surveyed historic collecting localities in south central Arizona dining JuK, August, and September 1993-94 to determine the presence of 3 little-known Sonoran Desert anurans, Biifo retifoniiis. Gastrophnjne olivacea, and Pternoliyla fodiois. All 3 species were present at most historic localities visited under appropriate conditions (fol-lowing rainfall in JuK' and August). Pternohijla fodiens was restricted to San Simon Wash and associated tributaries in south central Pima County. Gastrophnjne olivacea ranged from Vekol Valley in extreme southern Maricopa County south to the Mexican border, and southeast near Tucson and Nogales in Pima and Santa Cruz counties. Bitfo retifonnis occuiTcd over the widest area, from southern Rainbow Valley in Maricopa Coimty southwest to the vicinit>' of Organ Pipe Cactus National Monument, and southeast to the vicinity of Tucson and Sasabe in Pima County. Key tcords: Bufo retifonnis, Gastrophiyne olivacea, Pternohyla fodiens, historic distribution, present distribution, ainpliibian decline, Arizona, Sonoran Desert. Three relatively little-known anurans, Bufo retiforDiis, Gastrophnjne olivacea, and Pterno-hyla fodiens, occur in the Sonoran Desert in south central Arizona. Although placed in sep-arate families (Bufonidae, Microhylidae, and Hylidae, respectively), they are superficially similar in behavioral ecology. Each is inactive for more than 10 mon each year, emerging only to reproduce and forage following intense rainfall during the summer "monsoon' season. All exhibit "explosive" breeding behavior (Wells 1977) in which males form high-density aggre-gations for a few nights (sometimes only one) following a major rainstorm and call to attract females. Within Arizona all 3 species are largely restricted to a small portion of the Sonoran Desert in the extreme south central part of the state, so it is perhaps not suiprising that they are relatively unknowii. Indeed, Bufo retifonnis was described in 1951 based on specimens collected southeast of Ajo in 1948 (Sanders and Smith 1951), and Pternohyla fodiens was first documented in Aiizona in 1957 (Chrapliw>' and Williams 1957, Williams and ChraplivvT 1958). Given limited information on these Arizona aniuans, this investigation was undertaken in 1993 and 1994 to ascertain th(>ir present dis-tribution in Maricopa, Pima, Pinal, and Santa Cruz counties, Arizona. First, we describe methods used in conducting the suney. Then, for each target species sun^eyed, we describe distinguishing acoustic characteristics and out-line historic and present distributions. Last, we present observations on breeding behavior. Materials and Methods Suney Methods All surveys were conducted along paved roads throughout the known ranges of the 3 target species following rainstorms during July, August, and September 1993-94. Given the highly unpredictable and variable nature of summer rainfall and the need for monitor-ing the entire south central portion of Arizona, we could only crudely estimate (e.g., weather reports) the appropriateness of field condi-tions (i.e., le\el of rainfall) for anuran activit\ prior to each field excursion. Whenever suffi-cient rainfall appeared to have fallen in the study area, we traveled to that particular area on the night of the rainfall exent, or the fol-lowing night, to surve\' for amphibians along roadways. Frequently, 2-3 nights of surveying occurred for each rainfall exent. Occasionally, siu\'e\-plans were adjusted to take advantage of local conditions (e.g., localized flooding). I|)i-pai(iiit'iil of Life Sciences, Arizona State Universit\-West, PC) Box 37101). Phoeni.v, .\/. 85069. -Department of Biolosy, Clendale Comnuniit>' College, Glendale. AZ 85302. ^Department of Zoology; Arizona State University', Tenipe, AZ 85287. 38

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Arizona distribution of three Sonoran Desert anurans: Bufo retiformis, Gastrophryne olivacea, and Pternohyla fodiens

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