Breeding Behavior of the Western Chorus Frog

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Figure 1. Frogs of the Pseudacris triseriata complex in amplexus on the night of 9 April 2004 at Rogers Lake. Photo by Erik F. Enderson

Breeding Behavior of the Western Chorus Frog (Pseudacris triseriata complex) in Arizona Do Chorus Frogs call in the snow on the Colorado Plateau ? Kit B. Bezy1, Robert L. Bezy2, Kathryn Bolles2, and Erik F. Enderson3 1 Northern Arizona University, Flagstaff, Arizona 86001, USA 2 Natural History Museum of Los Angeles County, Los Angeles, California 90007, USA 3 2627 S. Jaguar Rd., Tucson, Arizona 85730, USA

Chorus Frog of the Pseudacris triseriata species

complex are the most boreal amphibians found in Arizona, ranging north to near the Arctic Circle in Canada’s District of Mackenzie and to above 3,670 m (12,000 ft) elevation in the Uinta Mts. of Utah (Stebbins 2003). The Arizona populations constitute the extreme southwestern limit of the distribution of the complex and are found from the White Mts., (Apache Co.), northwest along the Mogollon Rim to at least the vicinity of the Kachina Peaks (Coconino Co.), and in the Chuska Mts. (Apache Co.; Fig. 2; pers. obs.; Lowe 1976; Platz and Forester 1988; Stebbins 1951, 2003; Wright and Wright 1949). Across the vast range of the complex, considerable differences exist among populations in locomotory behavior, advertisement calls, morphology, allozymes, and mitochondrial DNA, and some areas of sympatry have been documented, but identification of species lineages remains problematic (summaries in Moriarity 82

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and Cannatella 2004; Platz 1989). Sampling has been particularly sparse in the western part of the range, and we here use “P. triseriata complex” for the populations west of the Mississippi River (including Arizona), rather than P. maculata. There is little published information on breeding activity of Chorus Frogs of the Pseudacris triseriata complex in Arizona. Wright and Wright (1949) reported that individuals were observed calling on the night of 8 June [1942] at “Mary’s Lake” and at Flagstaff (Coconino Co.). Platz and Forester (1988) found that the advertisement calls of 5 individuals from Potato Lake (Gila Co.) differed from other populations of the complex in several vocalization parameters. We here report our observations on breeding in the Flagstaff area in 2004. We observed frogs of the Pseudacris triseriata complex at 2 locations ca. 6 km southwest of Flagstaff: a pond along the eastern side of Rogers Lake (35º

09.097’N, 11º 46.237’W, 2207 m elevation; hereafter, “Rogers Lake”); and a small impoundment or cattle tank (35º 9.414’N, 111º 44.053’W, 2167 m elevation; hereafter, “the tank”). Observations of breeding behavior were made on 7 days between 26 March and 27 April 2004 (Fig. 3). Weather data are those recorded at Pulliam Airport (2130 m elevation), 9.3 km (air line) E of Rogers Lake. The study area was first visited on 26 March after a shower moved through the Flagstaff area (no precipitation was recorded at Pulliam). Between 1700 and 2100 hrs an estimated total of 10 individuals (including 1 female) of the Pseudacris triseriata complex were observed at the tank. At Rogers Lake, ca. 50 frogs were observed, including 1 calling within a rodent borrow. On 30 March, 1 individual was observed calling at the tank during the day at 1400 hrs. On 31 March, 10 frogs were observed calling at 1000

hrs at the tank, including 1 individual calling from a clump of grass in the water and a second individual clinging to the bark of a Pondorosa Pine (Pinus ponderosa). There were 6 individuals calling at the tank at 1700 hrs on 1 April. On 2 April when we arrived at the tank at 1630 hrs, snow was falling, the air temperature (AT) was 5.1ºC, and 5 Pseudacris were calling. By 2000 hrs the AT had dropped to 0.7ºC and 5 frogs were still calling. At 2030 hrs, the AT had fallen to –0.1; the water temperature (WT) was 7.1ºC, and 2 frogs were still calling. When we returned to the tank at 830 hrs on 3 April, the area was blanketed in snow (Fig. 4), the AT was 1.1ºC and WT was 6.5ºC; the overnight minimum AT recorded at the tank was 1.1ºC. At 1945 hrs snow again was falling and 2 frogs were calling (AT 0.7ºC, WT 6.1ºC). On 9 April , we arrived at the tank at 1750 hrs (approximately 1 hr before sundown) where 7 frogs were calling (AT 9.3ºC, WT 9.2ºC). At Rogers Lake at sundown (1850 hrs) a large chorus of ca. 25-35 frogs was observed (AT 7.1, WT 11.5). Some of the frogs were calling from grass clumps around the edge of the pond, but many were calling floating on the surface clinging to mats formed by the bent tops of grass. 4 pairs of frogs were observed in

Figure 2 Geographic distribution of the members of the Pseudacris triseriata complex in Arizona based on specimens in the Herpetology Collection of the University of Arizona (To date these are the only specimens for which we have verified the identifications of this species). Arrow indicates the two populations reported on in this paper.

Figure. 3 Weather data (daily maximum and minimum temperatures and precipitation) during March and April 2004 for the Flagstaff, Arizona area (Pulliam Airport). Vertical dashed lines below dots indicate dates of observations of breeding behavior of Chorus Frogs (Pseudacris triseriata complex) in the Rogers Lake region.

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amplexus floating on the surface of the pond. An individual (UAZ 55906) was found dead and dehydrated in a Ponderosa Pine (Pinus ponderosa) log

Figure 4 Photograph of the tank (3 April 2004) in which Chorus Frogs (Pseudacris triseriata complex) were calling on 2-3 April photo by K. Bolles

in the pond. A male was calling within a cavity of said log producing amplification of the sound. On July 10, ca. 7 juveniles were observed on the shore of the cattle tank, and no adults were apparent. By this time the tank had dried to ca. one half its diameter since 26 March. At Rogers Lake no frogs or water were observed at the site. On all dates where frogs were calling, we noted a temporary discontinuation of vocalization when automobiles passed on the road near the ponds and when aircraft passed overhead. Our observations indicate that in Arizona, members of the Pseudacris triseriata complex will continue to emit advertisement calls when the AT has dropped below 0ºC and while snow is falling. The low and rapidly falling air temperatures undoubtedly were ameliorated by the water temperatures which were 6ºC or higher, well above the minimum voluntary body temperature (BT) for the species of 4.1ºC (Fitch 1956). Moreover, Brattstrom (1963) has pointed out that Hyla regilla (Pseudacris regilla of 84

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Moriarity and Cannatella 2004) continues to call at a BT of 4.5ºC when temperatures are falling, whereas on rising temperatures it may defer commencement of calling until the BT reaches 10ºC. Our observations of a Pseudacris at Rogers Lake calling from a rodent borrow and of another individual (UAZ 55905) resting at 1740 hrs on the bottom of the lake at a depth of approximately 7 cm and 500 meters from shore suggest ways in which this boreal amphibian may avoid low ambient air temperatures. Acknowledgments Acknowledgments. We thank Erika Nowak (USGS Colorado Plateau Field Station and Department of Biological Sciences, Northern Arizona University) for information on activity of the species in the Flagstaff area, Bayard Brattstrom (Horned Lizard Ranch, Wikieup, Az) for discussion of thermal tolerances of amphibians, Gorge Bradley for making specimens in the herpetology collection of the University of Arizona

Figure1 Pseudacris triseriata complex vocalizing on the night of 9 April 2004 at Rogers Lake. Photo by Erik F. Enderson

available for study, and Erik Vose for reviewing an earlier draft of this paper. Literature Cited Brattstrom, B. H. 1963. A preliminary review of the thermal requirements of amphibians. Ecology 44:238-255. Fitch, H. S. 1956. Temperature responses in free-living amphibians and reptiles of northeastern Kansas. University of Kansas Publications of the Museum of Natural History 8:417-476. Lowe, C H. 1976. Amphibians and reptiles of Arizona. In: C. H. Lowe (ed.), The Vertebrates of Arizona. University of Arizona Press, Tucson. Moriarity, E. C. and D. C. Cannatella. 2004. Phylogenetic relationships of the North American chorus frogs (Pseudacris: Hylidae) Molecular Phylogenetics and Evolution 30:409-420. Platz, J. E. 1989. Speciation within the Chorus Frog Pseudacris triseriata. Morphometric and mating call analyses of the boreal and western subspecies. Copeia 1989:704-712. Platz, J. E., and D. C. Forester. 1988. Geographic variation in mating call among the 4 subspecies of the Chorus Frog: Pseudacris triseriata (Wide). Copeia 1988:1062-1066. Stebbins, R. C. 1951. Amphibians of Western North America. University of California Press, Berkeley. Stebbins, R. C. 2003. A Field Guide to Western Reptiles and Amphibians. Third Edition. Houghton-Mifflin Co., New York. Wright, A. H., and A. A. Wright. 1949. Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Assoc., Ithaca.

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Itemized Expenses: Bank fee $4.00, Program Speaker Travel $385.00. Committee Reports Conservation – Dennis Caldwell. Phil Rosen is in need of volunteers for his project surveying populations of amphibians in and near Tucson. Saguaro National Park (East), in conjunction with the Rincon Institute, is attempting to establish populations of Rana yavapaiensis in ponds on properties adjacent to the Park. The brochure on Living with Venomous Reptiles has gone out for review and will be sent to Board members after the next draft. Ideas were discussed for getting the final product to a wide-spectrum of the public. Speakers Bureau – Taylor Edwards. 22 July – Taylor Edwards discussed Sonoran Desert reptiles in conjunction with Rural Metro Fire Department on Arizona Illustrated Program – Roy Averill-Murray. The lineup of speakers includes: 17 Aug – Kate Jackson 21 Sept. – Bill Radke 19 Oct. – Ed Moll 16 Nov. – Don Wilson 21 Dec. – Young Cage Old Business Civil Fines for Unlawful take of amphibians and reptiles – Taylor Edwards. The Board approved a letter to the AGFD Commission supporting adding amphibians and reptiles to ARS 17-314 and recommending the establishment of minimal civil fines for illegal take and/or possession of all species of native Arizona amphibians and reptiles. ORV Policy in National Forests – Taylor Edwards for Trevor Hare. The THS will be sending a letter supporting the new policy. AGFD Commission Orders – Roy Averill-Murray. Comments on the new orders are due by 13 August.

B O A R D M E E T I N G S Y N O P S I S 27 July 2004 Robert L. Bezy, Secretary Directors Present: Roy Averill-Murray, Bob Bezy, Young Cage, Taylor Edwards, Cristina Jones, Hans Koenig, Marty Tuegel. Directors Absent: Ed Moll, Roger Repp, Eric Stitt, Don Swann. Members Present: Dennis Caldwell. Treasurer’s Report – Marty Tuegel Beginning Balance $ 9,945.82 Deposits. 343.00 Expenses 389.89 Ending Balance 9,898.93 Speakers Bureau 750.00 Jarchow Award 160.00 FTHL Fund 211.00 C.H.Lowe Research Fund 3,244.00 General Fund 5,533.93 CRHSD (CD) $7,208,81

New Business Laptop – Taylor Edwards. The Society is soliciting the donation of a laptop computer that can be dedicated to interfacing with the new digital projector. Northwest Explorer – Edwards. Young Cage will be drafting a letter to this magazine addressing issues concerning living with reptiles. Content of THS Emails – Taylor Edwards. The Board members should be aware that THS emails are official and need to be carefully worded. Nomination Committee - Cristina Jones. Cristina wishes to get an early start on the nominating process and volunteered to serve with Marty Tuegel on putting together the 2005 slate of candidates. She will be seeking a person who is not a member of the Board as the third committee member.

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Itemized Deposits: Donation $140.00, Membership $90.00, Raffle $43.00, Speakers Bureau $50.00, T-shirts $20.00. SONORAN HERPETOLOGIST 17(8) 2004

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