To test the accuracy of this method, a "grid of traps" was constructed by using 8-1/2 by 11 inch sheets of graph paper with heavy lines each centimeter. The intersects of the heavier lines were considered as trap stations. A "home range" of circular shape, 200 feet (4 cm.) in diameter, with an area of 31,146 square feet (0.71 acre), was cut from a sheet of transparent plastic. Another "home range" was made in an oblong shape with rounded ends. This range measured 2 by 65 centimeters (100 by 325 feet) and had an area of 32,102 square feet (0.74 acre). Each plastic range was tossed at random on sheets of graph paper for fifty trials each. The range was outlined on the graph paper, then circles having a scaled radius of 25 feet were inscribed around each "trap station" within the range. The peripheries of the inscribed circles were then connected and the estimated home range was delimited by the exclusive boundary-strip method. The estimated range was measured by planimetering, and the data were compared with the known home range (Table 2). It was found that when calculated by the exclusive boundary-strip method, the circular home range was overestimated by 2.22 per cent. The oblong home range was overestimated by only 1.50 per cent. Stickel (1954:4) has shown that the exclusive boundary-strip method is the most accurate of several methods of estimating home ranges, and in her experiments this method gave an overestimate of two per cent of the known range. Thus, my method of encircling the peripheral stations yields results that are, on the average, as accurate as the more involved method of inscribing squares about the trap stations, and saves a great deal of time as well. My method probably yields better accuracy; a perfect circle is easily drawn by means of a compass, whereas a perfect square is more difficult to construct without a template. It is generally understood that the estimated home range of an animal tends to increase in size with each additional capture; this increase is rapid at first, then slows. Theoretically, the more often an animal is captured, the more reliable is the estimate of its home range. Most animals, however, rarely are captured more than a few times. The investigator must decide how many captures are necessary before the data seem to be valid for estimating home ranges. An animal must be trapped at a minimum of three stations before its home range can be estimated, and even then the area enclosed in the triangle will be much less than the actual home range. Some investigators have plotted home ranges from only three captures (Redman and Selander, 1958:391), whereas others consider that far more captures are needed to make a valid estimate of range (Stickel, 1954:5). TABLE 2--Summary of Data from Experiments in Calculating Home Ranges for an Artificial Population.