. The Canadian field-naturalist. 92 The Canadian Field-Naturalist Vol. 80 Point Barrow ^ \ High A 1 \ Med. \ \ I J I \ Lemmus Low >, v v_ A J A k 0 D F A j7 k 0 D F A J A 0 D F A J A 0 D FA High Med, Low. I960 Figure 2. A hypothetical curve of changes in the number of trappable lemmings (Dicro- stonyx and Lemmiis) at the northwest corner of Aberdeen Lake, 1959-1963, based on adjusted snap-trap indices (see Table 1). The indices are shown as "x's". For com- parison, the relative abundance of the two species, according to Krebs (1963), 115 miles to the east at Baker Lake, is shown b
. The Canadian field-naturalist. 92 The Canadian Field-Naturalist Vol. 80 Point Barrow ^ \ High A 1 \ Med. \ \ I J I \ Lemmus Low >, v v_ A J A k 0 D F A j7 k 0 D F A J A 0 D F A J A 0 D FA High Med, Low. I960 Figure 2. A hypothetical curve of changes in the number of trappable lemmings (Dicro- stonyx and Lemmiis) at the northwest corner of Aberdeen Lake, 1959-1963, based on adjusted snap-trap indices (see Table 1). The indices are shown as "x's". For com- parison, the relative abundance of the two species, according to Krebs (1963), 115 miles to the east at Baker Lake, is shown by an "L" for Leimniis and a "D" for Dicrostonyx. Lemming Numbers Table 1 and Figure 2 show the lemming indices obtained: in the figure they are joined by curves representing the supposed relative population size for the intervals between trapping periods. Figure 2 also includes an estimate of lemming numbers in 1959, based entirely on casual observations made near the study area. The relative abundance of lemmings in the latter half of July at Aberdeen Lake and Baker Lake, as estimated on the basis of intensive studies by Krebs (1963 and 1964, and in litt.) is shown in Table 2. Differences between the two sets of indices for Aberdeen Lake exist in part because those of Krebs are based on a July trapping period, whereas mine are means of June and July trapping periods. As might be expected, Krebs' indices compare better with the July figures from Table 1 alone. His figures were based on a much larger number of trap nights (645' in 1960 to 2,226 in 1962), but are perhaps less directly comparable from year to year. The productivity of the two sets of trap lines also differed greatly. Krebs' traps were set accord- ing to a standard grid pattern, and caught their maximum of 15 lemmings per. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations m
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