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


TURTLES

The turtles and tortoises are very poorly represented in the reptilian fauna of the Pacific Coast, and only one species reaches the Yosemite National Park area.

This group of reptiles is well known to nearly everyone, for their very specialized protective shell is a feature not found in any other of our American reptiles. The scaly body covering of the reptile division is still plainly seen, especially on the legs; however, the upper and lower shells, commonly called carapace and plastron, are so modified that their scale characteristics are practically lost.

Like most of the other reptiles they possess sharp claws on their toes, a feature which helps to distinguish the reptiles from the amphibians. Their jaws are quite unlike the lizards or snakes for they do not possess teeth, and furthermore, the jaws are modified into a type of beak.

A majority of the turtles and tortoises have not ventured far from water, but a few have managed to exist on land, some actually going so far as to adjust even to the arid deserts of the southwest. All seem to be rather variable in food habits, with both animal and plant food being taken. Those forms that live in ponds or streams secure their food either in the water or near the water’s edge, and some even seem to be unable to swallow unless the head is submerged beneath the surface of the water. For protection the pond and stream types dive to the bottom of the pond either to partly bury themselves in the mud, or to become lost to view in the depths of the water.

In regions where winter temperatures drop rather low, turtles may hibernate during the coldest winter months. In common with many of the reptiles, they deposit eggs that have a very leathery shell. These are buried in sand or decaying vegetable matter where incubation takes place, the parent showing no interest in the young.

Unfortunately, perhaps, because of the brightly colored shells of the young of many species of turtles, these tiny specimens are now handled in the pet shops and each year are sold by the thousands. Because so few people know or seem to care about them, after the novelty has worn off, they are often left to starve, or in many instances, are gently dropped out the back door. A number of the latter find their way to ponds where they soon establish themselves, so that today the naturalist can never be sure that the turtles he observes in the ponds and streams are native there, or whether man has been involved in their unnatural distribution.

WESTERN POND TURTLE
Clemmys marmorata

The western pond turtle is found only in the lower elevations along the western boundary of the Park, and to date has been collected only from the vicinity of Swamp Lake, near Eleanor Dam, and in the Miguel Meadows. These turtles are fairly abundant at lower elevations in the San Joaquin Valley.

This turtle is only about eight inches long when fully mature. The top shell (carapace) is dark brown or blackish in color, but each individual plate is marked with yellowish spots or lines, the latter sometimes tending to radiate from the center of the plate. The plates of the carapace are relatively smooth, not roughened. The individual plates in the undershell (plastron) are mainly yellowish in color but are often bordered with black. The legs, head and neck are generally brownish, but often spotted with black or yellow.

These turtles are difficult to observe because they seem to dive into the water at the slightest disturbance and remain submerged for some time. They crawl out on logs or rocks that project above the surface of the water and there sun themselves for long periods unless disturbed. Fishermen are often surprised to find that these turtles will take a small hook baited with meat or worms. These turtles are sometimes utilized for food, and occasionally will be found displayed in the markets along the Pacific Coast. It is doubtful if many visitors will ever see this turtle, for its habits and the fact that its range is limited in Yosemite causes it to be one of the least seen of our reptiles, except of course, for some of the nocturnal snakes.



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