MICE by Ross Hardy Yes, mice! Unfortunately the vision conjured up by the word "mice" in the minds of most people is extremely unpleasant. This is undoubtedly because the average person is unfamiliar with mice, or because of a few contacts with the destructive European house mouse which is prevalent. Many are able to rationalize and find reasons why they dislike mice, but few have taken time to scientifically investigate the facts. Over 250 kinds of native Utah mammals include about 75 per cent rodents, most of which are mice. The European house mice and rats belong to and old world family of rodents distinct ffrom our native forms. Native Utah mice belong to three different families: the kangaroo-rats and their relatives; the jumping mice; and the white-footed mice, meadow mice and relatives. The numbers of mice are unknown, although various estimates usually based upon trapping records, have been mad. Dr. Lee R. Dice of the University of Michigan estimated that in late summer of 1935 there were about 2,500,000 individuals of the white-footed mouse in about 5,000 square miles of the Black Hills of South Dakota. A recent article in Life Magazine illustrated by Richard Grossenheider estimated that there are about 21,350,371,200 white-footed mice in the United States and Canada. Utah with 82,184 square miles could possibly support about 41,000,000 individuals of the common Sonoran white-footed mouse. Other species of mice would not be as abundant as this species. Of what value are mice? In nature they play an irreplaceable role in the formation and maintenance of soil. In England, Charles Darwin spent nearly forty years studying the formation of soil through the action of earthworms and concluded that such animals were abundant practically everywhere and were the chief builders of the soil upon which our modern civilization depends. But in desert Utah, no earthworms exist except in cultivated lands, meadows, and streamside areas about five per cent of the total area. In place of the lowly earthworm, Utah has yes, you guessed it MICE! Yes, mice are the soil builders. Here is Thomo-mys, "heap mouse," the pocket gopher 35 kinds of them busily piling mounds to cover vegetation and build such humus into the soil. Dipodomys, the "Two-footed mouse" or kangaroo-rat 23 kinds of them dig and tunnel. Their burrows lead air and water underground, moisten and aerate the plant roots and help to prevent flash floods. Pocket-mice, white-footed mice, canyon-mice, kangaroo-mice, sagebrush voles, and many more do their share in working over the soil, leaving their nitrogen-rich wastes and their bodies to build this soil. They plow, harrow, and fertilize the rangelands as thoroughly as man does his farmlands. And mice are seed planters. Busily harvesting seeds for the winter season, harvesting seeds for the dry season, planting them in tiny caches here and there, they forget to claim much of this food, and later tufts of grass appear here and there on the rangelands. In the forests, deer mice help squirrels and chipmunks in their tree-planting activities. Weeds are eradicated by mice through the destruction of seeds. In a normal rangeland which is not overgrazed by livestock, the plant balance is maintained by Nature through the activities of these numerous tiny servants. The harvest-mice particularly do valiant service here. Page Ten In New York forests, workers found rusts and similar fungus forest diseases are held partially in check by gnawing rodents which feed upon infected bark. Mice probably help in a minor way in this activity. Insects are decimated by the scorpion-mice and grasshopper-mice which feed upon the crickets, grasshoppers and other insects. White-footed mice and kangaroo-rats feed upon egg pods of the Mormon cricket. White-footed mice in the Canadian woods were found to be keeping down a harmful tree-boring insect by feeding upon the pupating forms. What will be the effect of wholesale poisoning upon such animals? In one section in Southern Utah this month, 10,000 poisoned baits supposedly for coyotes will be broadcast from an airplane. When mice are abundant, the activities of predators upon other forms of life will be minimized because the foxes, coyotes, bobcats, ringtailed cats, skunks, weasels, and relatives will be busily engaged in feeding upon such animals. Destruction of such mice by poison campaigns will turn the predators upon poultry and livestock in greater degree. One of the important fundamental contributions that biology has to make to society is an understanding of the vast interrelationships in nature and the way in which man may wisely manipulate these complex interlocking interdependences to his own benefit so that mankind may reap more abundantly of the living resources of nature. An understanding of mice and their place in nature is no small part of this necessary knowledge. Mice are also important in the laboratory. Many of the fundamental laws of nature as they apply to man have first been worked out upon mice. Mice have been used in the laboratory as test animals in many research problems pertaining to disease. Cancer, tuberculosis, leprosy, and other diseases too numerous to mention have been studied with the white European house mouse, the albino rat and the South American "Guinea pig." More recently, native white-footed mice have been used in the laboratory. Recent work in laboratories in New England states includes investigations into blood serums of white-footed mice. A few Utah specimens have been used in these investigations. The role of rodents in disease through their harmful activities as hosts for parasites carrying disease is also investigated. The study of nutrition problems, including the role of energy foods and vitamins in the body through the use of mice and rats, is so well known as to be almost proverbial. Hormone investigations have utilized mice. The Ascheim-Zondeck test for pregnancy works well upon them. In this test, urine samples are injected into young mice. If pregnancy exists in the person from whom the sample was taken, a pseudo-pregnancy shows in the mice within a short time. Radioactivity and its effect is studied through the use of mice. At the recent atom bomb tests at Bikini, white rats first cousins to the mice were taken along to determine the effect of the rays upon living tissue. The laws of heredity and their operation are being more thoroughly investigated than ever before at the University of Michigan where a "murarium" containing about 30,000 white-footed mice adjoins the Human Heredity Clinic. Much valuable information upon various eye defects, upon certain types of epilepsy, and many other ailments has been obtained. This information is based upon both mice and men. Thus mice have contributed to an understanding of the fundamental laws of health, of heredity and of conservation. Other fundamental laws which apply to many kinds of living organisms are demonstrated by mice. Many interesting adaptations to environmental conditions are displayed by these adaptable animals. The relationship between mice and the surrounding soil colors, soil depth, plant cover, and similar conditions are a never-ending source of information to the naturalist, revealing the way in which evolution is working in the world today as well as in the past. The laws governing fluctuations of populations and cyclic rhythms are at work among the native mice and can be discovered in such populations. The laws of predation and survival, of isolation and adaptation, are easily demonstrated among such animals. Here, too, mice can offer much to enrich mankind's knowledge of his environment. Appreciation of nature can be promoted through an understanding of these mice and their habits. Numerous species are valuable from the standpoint of an artist familiar with them, as well as from that of a photographer with a modicum of skill. Writers have a wealth of material to exploit. Harris in his Uncle Remus stories, Burgess in his nature stories, Disney in his cartoons have never failed when they have allowed Johnny Meadow Mouse and some of his relatives to appear. The taxidermist has a wide field among the hundreds of kinds of mice in America. Yes, mice have made their contribution to men. And the lady who says that she is afraid of mice and that she dislikes mice has benefited too. If you do not think so, look at that lovely fur coat made from the skins of an overgrown mouse a muskrat! Page Eleven