FIGURE 2. Demographic parameters contributing to the change in adult sex ratio in the deer population of the north block after 1972 (see Fig. 1c).

Open circles, females; filled circles, males. a, Percentage of calves born each year that were male plotted on population size (males and females), after effects of winter weather were controlled for (from ref. 13). b, Probability of mortality of male and female calves in the first three months of life. Mortality over this period was not density-dependent in either sex^4,5. c, Probability of mortality of males and females in the first 24 months of life (males, ² = 3.46. d.f. = 1, P < 0.1; females, ² = 7.14, d.f. = 1, P < 0.05)¹⁴. d, Probability of mortality of males and females among 5–10-year-olds (males, ² = 0.12, d.f. = 1, P > 0.05; females, ² = 4.48, d.f. = 1, P < 0.05). e, Emigration rates (proportion of residents permanently leaving per year¹⁵) of males and females (males, ² = 4.6, d.f. = 1, P < 0.05; females, ² = 0.8, d.f. = 1, P > 0.05). f, Immigration of males and females (number of permanent immigrants per year¹⁵) (males, ² = 11.8, d.f. = 1, P < 0.01; females, ² = 0.12, d.f. = 1, P > 0.05).