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Reptiles and Amphibians of Yosemite National Park (1946) by Myrl V. Walker


TOADS

Nearly everyone is acquainted with our common toads. The toads have become quite tolerant of civilization and have found the garden a good place to secure food and with the necessary moisture to keep their warty skins functioning properly in the process of respiration. The gardener is also well aware of their economic value, for he has no doubt seen them snap up many bugs, beetles, and other pests of the garden. Often they gorge themselves until they are hardly capable of hopping, but instead their movements are limited to an awkward crawl.

Although their warty skin helps to prevent loss of body moisture, they are still somewhat limited in their range. They are more active at night than in the day time. They spend most of the day in a small burrow or shelter that they have formed by literally “backing down” into the moist soil. The toads have a sharp tubercle on the inner sole of the hind foot that assists them greatly in this backward digging activity.

The adults live on land, often some distance from water, but once each year they return to the ponds and streams to deposit their long double-strand string of eggs. Here the young tadpoles (larva) hatch and for some time live in the water very much like a fish, for they have only gills—no lungs or legs —in the tadpole stage. Some toad tadpoles require several months to grow up and do not acquire their legs or lose their tail until the next summer season rolls around.

In all areas where seasonal variations are severe, the toads hibernate in the winter time, burrowing down in the soil, in old gopher roles, or in cracks alongside buildings, until they reach a point where they are safe from frost and freezing weather.

Although toads have warts, they do not cause warts to grow on human hands that touch them. The warts on the toad help him to conserve his skin moisture, and secondarily may secrete a substance that is somewhat poisonous if taken internally, or if it touches delicate membranes like those in the eyes; but on the hands it is generally harmless. Any dog that makes a mistake and takes a toad in his mouth suffers for his foolishness. This secretion seems to afford the toad some measure of protection.

Toads have also developed a rather large bladder-like organ which is used for water storage. This is something that the toad can draw upon to keep his skin moist if he gets too far from moist soil or leaves. The almost clear, colorless liquid often discharged by toads when first picked up is this supply of storage water, for its weight often greatly hinders the movements of the toad. He simply lightens his load by discharging this water, which has absolutely no poisonous or irritating properties.

Only two species of toads are found in Yosemite National Park. They are usually easily distinguished, not just because of their color variation and size, but because they each occupy a particular altitudinal range or habitat.

CALIFORNIA TOAD
Bufo boreas halophilus

CALIFORNIA TOAD
[click to enlarge]
N. P. S. Photo by Anderson
CALIFORNIA TOAD

This large toad is commonly found in Yosemite Valley and other areas in the Park at comparable elevations. It does not appear to live above 4,500 feet in elevation, so that there is an unoccupied space of nearly 2,000 feet, that is, between 4,500 and 6,500 feet where few if any toads are found, for the other species of Bufo, the Yosemite toad, does not descend to elevations below 6,500 feet.

The California toad has a much heavier body than the Yosemite toad; in fact, they are so bulky that they seldom hop as do most toads, but instead move forward in a most interesting slow awkward crawl. In the daytime they hide under boards or fallen logs, under flat stones, or even occupy the open burrows of field mice or ground squirrels. At night they come out to feed, and are often seen under the street lights where they have been attracted by the large number of insects which often gather around the lights.

These large toads have suffered greatly because of our modern age. The asphalt surfaced highways which retain many small pools of water after light summer showers, especially evening showers, seem to attract many toads. Here they are killed by the hundreds because with their slow awkward crawl they cannot escape the wheels of the motor cars that dash down the roads at terrific speed.


YOSEMITE TOAD
Bufo canorus

This small toad with its peculiarly rounded parotoid glands and strange sexual dimorphism has been found thus far only in or near the Yosemite National Park. Within the Park its range seems to be very limited, that is, to areas at or above 6,500 to 7,000 feet, and only in wet meadows. The Yosemite toad was first discovered by members of the University of California

YOSEMITE TOAD
[click to enlarge]
N. P. S. Photo by Anderson
YOSEMITE TOAD
scientific expedition when they were making their study of the fauna of the Yosemite National Park region in 1915. The Yosemite toad differs from the California toad in many respects. They are considerably smaller, they have fewer and smaller “warts,” and they have a very peculiar spring song, a long melodious trill, hence their specific name canorus. As they live at high elevations where the winters are long and snow remains on the ground for several months, these toads must hibernate for five or six months each year. They appear to be solitary at all times except during the spawning season when both males and females may be found near pools in the larger meadows.

Yosemite toads in our collection have come from near Mount Dana at 10,000 feet elevation, Research Reserve at 8,300 feet, Kerrick Meadow at 9,300 feet, Slide Canyon at 10,000 feet, Lyell Base Camp at 10,400 feet, Virginia Canyon at 10,000 feet, and near Upper McCabe Lake at 10,600 feet.



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