Interactions Between Organisms and

Abstract

This is difficult because it is first necessary for the ecologist to have some knowledge of the neurological and physiological detection abilities of the organism. Sound, for example, should be measured with an instrument that responds to sound energy in the same way that the organism being studied does. Snow depths should be measured in a manner that reflects their effect on the animal. If six inches of snow has no more effect on an animal than three inches, a distinction between the two depths is meaningless. Six inches is not twice three inches in terms of its effect on the animal! Lower animals differ from man in their response to environmental stimuli. Color vision, for example, is characteristic of man, monkeys, apes, most birds, some domesticated animals, squirrels, and, undoubtedly, others. Deer and other wild ungulates probably detect only shades of grey. Until definite data are ob- tained on the nature of color vision in an animal, any measurement based on color distinctions could be misleading. Infrared energy given off by any object warmer than absolute zero (-273°C) is detected by thermal receptors on some animals. Ticks are sensitive to infrared radiation, and pit vipers detect warm prey with thermal receptors located on the anterior dorsal portion of the skull. Man can detect different levels of infrared radiation with receptors on the skin, but they are not directional nor are they as sensitive as those of ticks and vipers. Thus we must conclude that the environ- 16 ------