By Charles M. Bogert, Ranger Naturalist
THE STATE OF ARIZONA, with remarkable diversity in topography and a correspondingly intricate life-zoning, contains numerous species of reptiles, birds and mammals as a result. But with the amphibia it is a different story. Salamanders, frogs and toads, because they are necessarily aquatic in the early stages, are confined to more restricted habitats. Arizona, a comparatively arid state, contains very little swamp land and while there are rivers of importance, they are not of the old, meandering type that brings about the most suitable ecologic conditions for amphibians.
So, the state of Arizona is probably one of the poorest in amphibians. With twelve species it may be contrasted with Oregon which has eighteen and with California which has thirty-five species.
Within the limits of Grand Canyon National Park only four species have been recorded to date, although there is strong possibility that two or three others will be discovered here. Environment alone seems not to be the only factor governing the distribution of amphibians, as the introduction of new species into some areas has demonstrated. It is interesting to conjecture regarding the presence of amphibians at desert oases, the Rocky Mountain Toad, Bufo woodhousi, for instance. Have these been carried there by other animals such as birds, or are they remnants possibly surviving from a time when the entire area was within a moist climate?
The only tailed amphibian in Arizona, the Tiger Salamander, Ambystona tigrinum, called axolotl* in the larval stage, is known from the tanks on the South Rim and from Greenland Lake on the North Rim. The larvae are rather common in these pools of water but to date I believe only two adults have been found.
Two other amphibians known in the Park are more numerous. The Sonoran Tree Toad, Hylla aernicolor, is common about permanent shady pools in the canyon bottoms. This species was observed to be especially common around the pools below the falls in Havasu Canyon.
But the Spotted Toad, Bufo punctatus, is the commonest of the three. During rains they come forth in great numbers and while they are more prevalent in the canyon bottoms at such places as Indian Gardens, Burro Springs, etc., they range up near and perhaps to the South Rim, Between rains refuge is sought in crevices in the rocks or at places where there is a slight seepage. One hot day in July a barrel of water near the stable at the mouth of Bright Angel Creek was overturned and nineteen toads were found beneath it.
During the latter part of July Bufo punctatus was observed mating and egg-laying at Indian Gardens and near Phantom Ranch. This is rather later than most southwestern toads lay eggs and may prove to be of some interest. At Indian Gardens the eggs, in long strings, were found in a shallow pool separated from the main stream.
What is apparently the first occurrence of the Spadefoot Toad, Scaphiopus hammondii, to be reported from within the limits of Grand Canyon National Park, was published in Grand Canyon Nature Notes for October, 1932. Mr. Wallace F. Wood found the larvae and newly metamorphosed young of this toad in Greenland Lake on the North Rim, July 1, 1932.
The Spadefoot Toad is apparently widespread in occurrence and common throughout the Southwest, but it is one of the most secretive of the amphibia. During the breeding season in the early part of July they are sometimes found in numbers around pools, but the remainder of the year it seems to be impossible to find them.
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