Amphibians of the Vekol Valley

Figure 1. Green Toad (Bufo debilis, UAZ 54811) from Hidalgo Co., New Mexico. Note that the color pattern resembles that of the specimen in Fig. 2 in having the dark markings not joined into a reticulated network. Photo by Erik Enderson. Amphibians of the Vekol Valley Erik F. Enderson1 and Robert L. Bezy2 1Drylands Institute, PMB 405, 2509 North Campbell Avenue, Tucson, Arizona 85719, USA. 2Natural History Museum of Los Angeles County, Los Angeles, California 90007, USA. This winter (2005) a landmark publication, Dry Rosen; and finally, Sea Turtles and the Alto Golfo: A Borders: Great Natural Areas of the Sonoran Desert Struggle for Survival by Jeffrey A. Seminoff and (Richard Felger and Bill Broyles, editors, University Wallace J. Nichols. The Vekol Valley chapter is of Utah Press) will become a first for conservation presented here for the first time, in a slightly edited and ecological writing. This book is a rich blend of version for the Sonoran Herpetologist. science and literature from noted authors in Mexico, Richard Felger and Bill Broyles the U.S. and Canada that includes 41 chapters and gives a fresh view of the Sonoran Desert, from the It’s the kind of place you can get stuck in for days – Gulf of California to the Gran Desierto. It is vast and remote, harsh and mysterious - a place where scientifically accurate and highly readable by a even the heartiest can become queasy. And although broad audience. The book contains more than 400 today a few reminders of civilization can be seen, there illustrations including the compelling photos by still remains a sense of total isolation when you are Pulitzer Prize-winning photographer Jack Dykinga. within its confines. It is Vekol Valley; an untamed, This work presents marine and desert ecology and unique, bizarre, and ecologically rich region of Sonoran natural history, biodiversity, human history, and Desert. It is the uniqueness of the Vekol that lured us, biographical information for education, science, and specifically, the presence of one toad. conservation. We were drawn into the valley by an animal Much of the region's rich herpetofauna is known as Bufo debilis (the Green Toad). This described in three chapters: The Amphibians of the amphibian occurs throughout the Chihuahuan Desert Vekol Valley by Erik F. Enderson and Robert L. from northern Mexico through Texas and New Bezy; Reptiles and Amphibians of Arid Southwest- Mexico to southeastern Arizona. Sometimes considered ern Arizona and Northwestern Sonora by Philip C. a Chihuahuan indicator species, in Arizona it thrives in 74 SONORAN HERPETOLOGIST 18 (7) 2005 the semi-arid grasslands of the state’s southeast corner colorful masses appeared to be right on target and had not been found west of the upper San Pedro sweeping slowly northwest, their size and intensity Valley. That changed, however, in 1983 when three growing as they approached the Vekol, only to burst BLM biologists reported the surprising occurrence of and whither away when they hit what we estimated B. debilis in the Vekol together with its nearest to be the position of Table Top Mountain. Whether relative, Bufo retiformis (the Sonoran Green Toad; any rain may have spilled over into the Vekol was a Jones et al. 1983). judgment call. In desperation we sometimes decided The Vekol Valley lies well within the Sonoran to head out on the long 99 mile (160 km) excursion Desert with luxuriant Arizona Upland Desert on the just to verify that the cells did not reach the Vekol. upper bajadas and stands of Creosote (Larrea On more than one occasion large rain-filled puddles divaricata) dominating the lower slopes. The latter are and the smell of wet creosote greeted us as we passed mapped as Lower Colorado Desert, the hottest, driest north of Table Top on the highway, only to find of the North American deserts, where highs may reach parchment–like conditions as we dropped into the 50°C (120°F) and some years rain does not reach the Vekol. ground, not exactly where one would expect to find Eventually our persistence paid off and the Bufo debilis. But the Vekol holds a wild card. In its torrential summer rains struck the valley, bringing southern reaches exists the remnant of what once may with them an amphibian breeding frenzy, the likes have been an expansive and spectacular Tobosa of which we had not previously seen or heard grassland community, the same grassland community outside of the tropics. The normal nocturnal silence that supports Bufo debilis in the Chihuahuan Desert was replaced by the calls of thousands, perhaps tens regions to the east. We wondered if the Green Toad, of thousands, of vocalizing frogs. Some nights their like the Tobosa grassland and Antelope Jack Rabbits numbers were so great, it was difficult to avoid (Lepus alleni) we had observed in the Vekol may be stepping on them. The once dry pools and ponds relicts that have been isolated in the Sonoran Desert were now filled to the rim. Mesquite trees stood like since wetter times prevailed over 10,000 years ago the giant cypress trees in the bayou of the Southeast, It all sounds so (Van Devender 1990). The question intrigued us and with two feet (0.6 m) of water extending up the in the summer of two thousand the time seemed right trunks. The ponds were soon to be bursting with pleasant - nature to investigate. tadpoles. A week would pass and the tadpoles will at harmony with What ensued were three summers of axle- have metamorphosed into toadlets, so small they fit grinding, tire-spinning muddy roads and endless into the cracks of drying mud, protecting their itself, sharing its nights sloshing through the sloughs of rain-hydrated porous skin from the relentless desert sun. Come cow excrement, fending nightfall those same wonders with the off ravenous mosquitoes, cracks serve as a hub to eager biologists. and crawling through the new community some of the densest bustling with nocturnal But don’t be mesquite bosques in the activity. fooled. The thorny Southwest. The nights It all sounds so yielded adventure, pleasant - nature at Vekol is not a surprise, and sometimes harmony with itself, disappointment. sharing its wonders with gracious host. the eager biologists. But Doppler-mania don’t be fooled. The Ominous red- thorny Vekol is not a centered masses ringed gracious host, and many with yellow and green of our trips were full of slowly develop in the late all manner of pain and afternoon over Sonora’s anguish, cruel and rugged Sierra Madre unusual punishment. Occidental and begin Figure 2. Museum specimen of Green Toad (Bufo debilis; USNM moving north. The 252776 reported from the Vekol Valley by Jones et al. 1983) that Follow That Call monsoon had arrived and stimulated this study. Photo by Erik Enderson. During our anuran bright Doppler radar (frogs and toads) images were again lighting up our favorite on-line surveys in the valley we used a common technique to weather maps. We watched and waited, sometimes for locate our subjects. It involves driving short inter- the entire night. It’s like a card game in which you vals, stopping the vehicle, silencing the engine, and evaluate your chances every 15 minutes as the new listening for a frog chorus. When the time and image unfolds on your screen. Some nights the conditions are right anurans can be heard vocalizing SONORAN HERPETOLOGIST 18(7) 2005 75 from great distances. Using our ears to home-in, we Toads) were present in the tank, we faced the would set off on foot to locate the breeding aggrega- depressing prospect of the return crawl. In a desper- tions, which, more often than not, were buried deep ate attempt to avoid the mesquite thicket, we within the thorny armor of Vekol’s immense mesquite explored the full length of levee, but nowhere bosque. around the enormous horseshoe-shaped structure did We left a glowing flashlight on the roof of the the bosque appear any more penetrable. We returned truck as we headed out into the darkness with our to our original point on the bank and began the long headlamps, camera, tape recorder, and high hopes. crawl out. We crossed the open grassland following the frog Soon after, we heard it. At first it sounded like a vocalizations arising somewhere deep in the mesquite hiss - maybe that of a Gophersnake (Pituophis grove dead ahead. At first the young mesquites were catenifer) intimidating a potential predator. The just shrubs, scarcely 9 feet (3 m) tall and widely sound seemed to come from all directions. Pausing in scattered across the open terrain. As the chorus grew mid-crawl, we turned off our headlamps and listened louder, the mesquites became large trees with intently—nothing but silence. We switched the interlocking branches. After eons of evolution, it is lights back on and the hiss resumed. As we crouched, difficult to forsake our noble upright posture and the noise seemed to grow louder, now only a few feet away. We scanned the ground around us and saw nothing that could explain the ominous sound. Finally, we shined the beam up into Figure 3. the trees and saw it - a massive, hissing swarm Lowland Burrowing of honey bees on the mesquite just above our Treefrog heads. Carefully and silently, we turned off (Pternohyla the lights and slowly crawled away. We were fodiens) from the unsure whether or not the bees in the Vekol Vekol Valley, the northernmost are “Africanized,” but the thought of trying known locality for to escape a swarm by crashing through the the species. Photo dense thorny mesquite tangle was not by Erik Enderson.

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