Investigations concerning the effects of several meteorological and seasonal factors upon fox squirrel activity were made over 250 acres of floodplain and upland terrain in Story County, Iowa. Duration of the investigation was from April, 1938 to March, 1941 and from February, 1946 to March, 1947;A spot count method and a linear count method were used to obtain counts of squirrels seen. The degree of squirrel activity was expressed by means of ratios between the number of squirrels seen and unit of time. One hour was used as the time unit; consequently, ratios varied in accordance with the numbers of squirrels observed;For each observation period of thirty minutes, concurrent values for temperature, relative humidity, wind velocity and barometric pressure were obtained. Data pertaining to degree of overcast, precipitation and depth of snow were recorded for each observation period;Approximately thirty-five hours of observation were accumulated for each of twelve months throughout the duration of the investigation. Thus, each month and each season had approximately equal representation. Observations were made at all daylight hours. However, fewer observations were made during early and late daylight hours than during those hours which are light throughout the year. No observations were made from 9:00 P.M. to 3:00 A.M;The investigation was executed to include extremes of all meteorological factors. However, observation periods characterized by these extremes were fewer than those periods characterized by mean and near mean values of weather factors;The data were analyzed with respect to each environmental factor considered to determine the relationship between the squirrel-hour ratios and the specific factor under consideration. In other words, variations in the amount of squirrel activity were used as a means of measuring the effects of each environmental factor as it varied from one extreme to the other. (Abstract shortened by UMI.)