94 F. BOURLIERE 



range types. The roe deer loss is due to emigration (Andersen, 

 1953) and that of the black-tailed deer to hunting (Taber and 

 Dasmann, 1957). Among the male dall sheep and the male 

 red deer there is little loss during the third year. 



(4) From the fourth year onward, to old age, the hunted 

 populations (roe deer, black-tailed deer and red deer) show 

 fairly steep losses in both sexes. The rate of loss tends to 

 lessen in full adulthood in the male black-tailed deer, pre- 

 sumably because learning and behaviour make these individ- 

 uals less vulnerable to hunting (Taber and Dasmann, 1957). 

 In the red deer, on the contrary, the rate of loss becomes 

 heavier in full adulthood because of the selection of prime 

 stags by sportsmen. 



(5) The dall sheep, which is not hunted, shows very little 

 loss from adulthood to 9 years old. If it were not for hunting, 

 the other ungulate populations would probably exhibit 

 survival curves rather more similar to those of Ovis dalli. As 

 Taber and Dasmann (1957) pointed out, it is nevertheless 

 doubtful that they could ever attain as high a survival as long 

 as their ranges were fully stocked and starvation was a com- 

 mon cause of death. In that connexion, it is interesting to 

 note that the survival curve of the barren -ground caribou, 

 which is hunted mainly by natives, is closer to that of the dall 

 sheep than to that of hunted deer. 



(6) In old age there tends to be in most cases a steepening 

 of the survival curve ; this accelerated loss may be due directly 

 or indirectly to senescence. In dall sheep we know, for instance, 

 that both the very young and very old animals were preferably 

 killed by wolves. Heavily hunted species do not display such 

 a pattern because the high kill permits few individuals to grow 

 old. 



On the whole, it seems that most of the differences between 

 these various populations of wild ungulates are not inherent 

 in the species, but rather imposed by environmental condi- 

 tions. If a roe deer population is fenced, emigration is pre- 

 vented but winter mortality due to starvation becomes high. 



