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Next: Insect-eatersContentsPrevious: Foreword

Mammals of Yosemite National Park (1952) by Harry C. Parker


HOW TO TELL A BEAR FROM A BEAVER

Mammals comprise those creatures with hair on their bodies and which suckle their young. These form but a small part of the animal kingdom; hence it would be inaccurate to restrict the term “wild animal” just to mammals, despite popular use to the contrary. After all, worms are wild animals; so are frogs; so are birds; so are millions of kinds of insects, just to name a few others!

For convenience in identification, scientists have divided mammals into several “orders” or large groups. Six of these are represented in the Yosemite list: Insect-eaters (Insectivora); bats (Chiroptera); flesh-eaters (Carnivora); rodents (Rodentia); rabbits and their allies (Lagomorpha); and even-toed, hoofed mammals (Artiodactyla).

Mole

Mole

Dental characteristics play a large part in this classification, and, in a general way, indicate the food habits of each group. This fact may assist in keeping the differences between orders in mind. We will, therefore, pursue the subject further, utilizing drawings of the skulls of typical Yosemite species made by Richard G. Miller.* [* See “Food Habits of Yosemite Mammals as Indicated by Their Teeth,” Yosemite Nature Notes, 24 (2-5), February, March, April and May, 1945.] The symbols that look like a row of fractions represent the number of teeth on one side of the face, reading from front to back, uppers and lowers.

The insect-eaters (moles and shrews) have very sharp teeth which are especially suited for cutting through the hard parts of insects and rapidly chopping up food. This even applies to the jaw teeth, which in most other orders serve as grinders rather than shears. The front teeth are long and sharp, useful for grasping and holding lively prey.

Big Brown Bat

Big Brown Bat

The scientific name for bats, Chiroptera, refers to the structure of the wing (Greek cheir, hand, plus pterone, wing), rather than to food habits (see p. 59). However, the teeth of Yosemite bats are specialized for catching and eating insects, so we may also think of them as “flying insectivores” rather than “flying mice” as is popularly supposed (see below, “Rodents”).

The canine or “eye” teeth of Yosemite bats are quite large and well suited for seizing and grasping. The jaw teeth are quite jagged and offset between uppers and lowers to provide a definite shearing action. This enables them rapidly to chop up and devour the many insects that are captured in flight.

Black Bear

Black Bear

The flesh-eaters (Carrnivora), typified by bears, dogs, cats, weasels and the like, have prominent canine teeth which, together with the strong incisors or front teeth, equip them for seizing and holding living prey. Powerful jaw muscles assist in biting and tearing. Most members of the order have sharp jaw teeth with blade-like crowns, well-suited for a scissors-like action in cutting and chewing flesh, tendons and bones. The bear is a notable exception to this condition, having broad, flat crowns on the jaw teeth which are more useful to such animals that eat almost anything, from ants to carrion.


Cony

Cony

Rodents, or gnawing mammals, are characterized by four chisel-like front teeth, two long uppers which overlap the two prominent lowers. These incisors are kept sharp by differential wear in the gnawing process. The front surface of the tooth is hard, wear-resisting enamel which remains as a sharp edge after the softer dentine has eroded back. The wearing down is compensated by continual renewal, the teeth pushing out from the roots deep within the jaws. The canines are lacking but there are competent jaw teeth for the grinding up of food cut by the incisors.


Aplodontia

Aplodontia

The rodent skull figured is from the mountain “beaver” or Aplodontia (see p. 64). If one is accustomed to thinking of rodents as being only small creatures, such as rats and mice, it should be remembered that the golden beaver (Castor canadensis subauratus) attains a weight in the neighborhood of 40 pounds, yet is very definitely a rodent!

Rabbits, hares and conies (Lagomorpha) outwardly resemble the rodents in many respects. The front teeth grow continually to compensate for wear, but the enamel ex[t]ends to the back surface of the tooth. There is also an extra pair of incisors, lacking the cutting edges, right behind the upper, front, two chisel teeth. The jaws of lagomorphs are so fastened that they chew with a sidewise motion, while in rodents there is considerable longitudinal action.

Mule Deer

Mule Deer

A good name for the hoofed mammals might be “toenail walkers,” for the hoof is actually a specialized toenail. Yosemite deer and bighorns, or mountain sheep, usually walk on the two large toenails on each foot and are therefore members of the even-toed, hoofed order of mammals, Artiodactyla.

Deer and bighorns have no upper incisors, but utilize the lowers very well in obtaining food by gripping vegetation against toothless upper “plate” and lips, then wrenching it loose. The greenery then goes into the rear of the mouth where it is ground between large, broad teeth. It then moves to the rumen, a compartment of the stomach which serves as a storage chamber. There the food remains in a half-chewed state until the animal is through foraging and finds time in a safe place to give it further attention. It is then brought up in cuds, chewed and reswallowed for thorough digestion.

The system of classification of mammals progresses downward from the orders through lesser groups having closer ties in structural relationship, such as families, divided in turn into genera (singular genus), species and subspecies. Such divisions are indicated in the checklist (see p. 104).

A discussion of the characters delineating these lesser divisions seems entirely beyond the limits of a work of this nature. However, it should be explained that the scientific names of the various species contain at least two parts, the first of which is the genus, the second the species, and, where applicable, a third, the subspecies. Subspecies, and in most cases, species, are based on comparatively minor differences in color, size, or structure of the skull and teeth and require the dead specimen in hand for final determination. Obviously such characters will not be readily observed in the park, where the wildlife is protected by law against molestation in any form.

Perhaps some concept of the nature of a scientific name can be gained by consideration of an artificial case, a hypothetical man whose name is John Adam Smith. Written as a scientific name, this would be “Smith John Adam,” latinized, of course. Smith may be compared to generic name, John the specific name, and Adam the subspecific, though technically, the example is not truly analogous.

There is a tendency on the part of mammalogists to use common names for species, but not for subspecies since the latter cannot usually be distinguished in the field, except sometimes on the basis of locality, correlated with its known range. Twenty years of experience in educational work have taught me that the layman wants common names for the different forms. Since well-established vernacular names for most Yosemite mammals have existed in the literature for many years, I have used them in this work wherever they were available. In certain instances, where the common name applied by Grinnell and other western authors was preceded by a name more widely known throughout the United States, I have favored the latter in order to make the booklet more useful to park visitors, who come from all parts of the land.



Next: Insect-eatersContentsPrevious: Foreword

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Online Library: Title Author California Geology History Indians Muir Mountaineering Nature Management

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