Most dispersal of marked yearling females fit the 

 description of pre-saturation dispersal (Lidicker 1978). 

 Seven of 9 dispersals by marked yearling females occurred 

 during the first 2 years of population increase. Only 2 radio- 

 collared yearling females occurred among the 1986 cohort; both 

 emigrated from the study area. Population estimates indicated 

 that up to 49% of the 1986 female cohort emigrated during 

 summer 1987 without an offsetting immigration. Dispersal 

 during other years was low or non-existent. Contrary to what 

 was observed for yearling males, emigration of yearling 

 females did not appear to be balanced by immigration during 

 any year, although some immigration may have occurred during 

 autumn 1983. 



The average date of dispersal was earlier for yearling 

 males than for yearling females (Fig. 8.3). Some yearling 

 males dispersed before their mother was actively aggressive 

 towards them, while few yearling females dispersed until their 

 mothers aggressively chased them. Yearling females stayed in 

 the same area as their mothers for some time, and active 

 aggression on the part of the mother was necessary to break 

 the close social bond that characterized doe-fawn 

 relationships during the first year. Yearling males appeared 

 to be inherently inclined toward dispersal but yearling 

 females did not. 



c 

 "55 

 a> 



Q. 



0) 

 

 Q 



60 "I 



50" 



40- 



30- 



m- 20- 



10" 



Males 

 Females 



ill 



Mid Late Early Mid Late Early 

 May May June June June July 



Late 

 July 



Figure 8.3 



Date of dispersal for yearling mule deer, 

 220 



