Field Notes on Hyla wrightorum Taylor

Abstract

W HEN the author left Ithaca, New York, in June, 1933, to join the U. S. Forest Service in Arizona, Dr. A. H. Wright asked him to be on the lookout for any specimens of the Sonora tree frog, at that time recognized as Hyla eximia Baird. More recently Taylor (1938: 436-9, P1. XLVII, fig. 1) has redescribed this frog, proposing for it the new name Hyla wrightorum. Data on this species have been collected during the past five seasons. During the first four of these, the author's connection with the Civilian Conservation Corps provided many willing collectors. RANGE IN ARIZONA.-To date the author has found this frog only on the southern forested edge of the Colorado Plateau from the vicinity of Williams east to McNary. The full range extends east to Texas and south into Mexico. The Colorado Plateau extends roughly east and west through central Arizona into New Mexico. The altitude is approximately 7,000 feet above sea level. In general the southern part is in the transition zone and is covered by typical vegetation including a broad belt of ponderosa pine with small areas of Douglas fir, white fir, Mexican white pine, and other trees. The pines are predominant in a mixture including species of oaks, junipers, and pifion pine; the particular admixture depending on local conditions. The frogs have been found throughout the forest. No specimens of Hyla wrightorum were found in the isolated Pinal Mountains, south of Globe, although they reach from upper Sonoran through the transition zones, ranging from 4,000 to 8,000 feet in elevation. No frogs were found in the large springs at Pinetop, whose waters have a temperature of about 50'F. The waters of open ponds are warmed during the day, and remain at a higher temperature. The lower limit of the distribution of the species in this region seems to be defined by the rim of the Colorado Plateau, with an elevation of 5,000 feet. The 1936 season was spent at Indian Gardens, 22 miles east of Payson, in an area directly beneath the rim of the plateau (here called the Mogollon or Tonto Rim). No specimens were found in this well forested area, though frogs were found on the plateau above on several trips. Hyla eximita was not listed for the Grand Canyon National Park (McKee and Bogert, 1934). Judging from the small number of specimens found, Williams is probably the western edge of this frog's range. Although the summer rains were few in 1937, they were heavy enough to have brought out all individuals, but very few were found. Many suitable ponds were completely barren. Continuing east, numerous specimens were found along the rim. At Hart Canyon, which is 50 miles south of Winslow, and at Pinetop and McNary the numbers in the summer ponds were very great. HABITAT.-Before and after the breeding season the frogs are found occasionally throughout the forest. Clever camouflage and ventriloquism aid them in escaping detection. They are found on the ground in damp places and in the trees. Twice the author found several which had been jarred loose when a tree was felled. In one of these instances, a frog fell from the