Coefficients of competition between mule deer and white tailed deer at the Dos

Coefficients of competition between mule deer and

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Coefficients of competition between mule deer and white-tailed deer at the Dos Cabezas Mountains indi- cate considerable potential for direct competition (Ta- TABLE 8. Mean number of plant species per fecal sample for deer in the Dos Cabezas Mountains from August 1969 to January 1972 (Numbers of samples in parentheses)' Season Deer species Dec to Jan Feb to Mar Apr to May Jun to Jul Aug to Sep Oct to Nov White-tailed deer 7.19 ? .51 6.50 + .69 9.79 ? .61 8.20 ? .61 9.75 + .61 8.75 ? 1.08 (27) (16) (19) (20) (20) (8) Mule deer 6.49 + .43 6.77 + .52 7.79 + .46 6.89 ? .62 7.71 ? .55 7.12 + .76 (37) (26) (33) (19) (24) (14) Values are: x ? (t 05) (standard This content downloaded from 129.219.247.33 on Mon, 10 Sep 2018 23:14:48 UTC All use subject to
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270 ROBERT G. ANTHONY AND NORMAN S. SMITH Ecological Monographs Vol. 47, No. 3 TABLE 9. Indices of overlap in spatial distributions, habitat selection, and food habits between mule deer and white-tailed deer at the Dos Cabezas Mountains (August 1969 to January 1972) Coefficient of competition Spatial Habitat Food distributions selection habits (S x H x F) (S + H + F)/3 Season (S) (H) (S x H) (F) product cc summation cc Apr to mid-Jul .66 .76 .51 .74 .37 .72 Mid-Jul to Oct .64 .66 .42 .77 .28 .69 Nov to Mar .57 .82 .47 .84 .39 .74 Seasonal x .62 .75 .46 .78 .35 .72 ble 9). We believe the product a: values are slightly conservative and the summation a values are overes- timates, so that the true multidimensional c are proba- bly in the range of 0.40 to 0.50. Interestingly, the coef- ficients for the critical time of the year (November- March) are highest and for the optimal time (mid-July to October) is the lowest. Recruitment Mule deer had a higher recruitment to their popula- tion than did white-tailed deer during the study (Table 10). The magnitude of this difference was not signifi- cant until 1971-1972 when recruitment for mule deer was nearly 2x that for white-tailed deer. Because a drought period preceded the 1971-1972 figures (An- thony 1976), this difference is quite informative. Over- all recruitment for mule deer was 7% higher than that for white-tailed deer. BEHAVIORAL INTERACTIONS Behavioral interactions between mule deer and white-tailed deer were evaluated in only those encoun- ters in which individuals or groups of individuals of the two species came close enough for antagonism or avoidance to be displayed by either species. Usually, the maximum distance at which any behavioral in- teractions between individuals became apparent was -45 m depending on the density of shrubs and trees; this distance agrees with the results presented by Kramer (1973:297). Encounters between the 2 species were more frequent in the Dos Cabezas area (1 1%) than in the San Cayetano area (3%) (Table 1 1). The difference in these frequencies reflects the sym- TABLE 10. Herd composition counts of deer in the Dos Cabezas Mountains during November through February 1969 to 1972 White-tailed deer Mule deer Fawns/ Fawns/ 100 100 Year Does Fawns does Does Fawns does 1969-1970 41 17 41.5 205 89 43.4 1970-1971 30 8 26.7 123 34 27.6 1971-1972 31 6 19.4 103 38 36.9 Totals 102 31 30.4 431 161 37.4 patric nature of the 2 populations in the Dos Cabezas Mountains and the almost mutually exclusive nature in the San Cayetano Mountains.
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