observable. Because hunter harvest may be extraneous to the 

 development of "natural" regulation of populations, it will 

 not be discussed here. However, hunter harvest is the major 

 factor we can control or manage and will be further discussed 

 in Chapter 13-Management Implications. 



The finding that variable weather is the major factor 

 influencing forage production and quality and population 

 dynamics of herbivores is not new (Talbot and Talbot 196 3, 

 Teer et al. 1965, du Plessis 1972, Hirst 1975, Sinclair 1977, 

 Medin and Anderson 1979, Croze et al . 1981, and Rogers 1987) 

 However, the tendency has been to assume almost perfect 

 operation of density-dependent reproduction and mortality 

 despite non-density related changes in forage conditions. 

 Under this assumption, reduction in density always increases 

 nutritional level and survival. In contrast, we maintain that 

 under unfavorable conditions the condition and fates of 

 individual animals vary as individuals, not as l/N. Thus, 

 during drought, a reduction of density by one-half as a result 

 of harvest does not mean that the remaining animals will all 

 survive because they now have twice as much to eat. In some 

 drought situations, any surviving animals have only sub- 

 maintenance quality of forage to subsist on and quantity is 

 not important. 



A careful reading of numerous papers (especially in 

 combination) indicated to us that weather related changes in 

 forage abundance and quality and animal distribution often 

 influenced large mammal population dynamics regardless of 

 density. Low density populations did not perform well during 

 unfavorable conditions, but high density populations could 

 perform well during favorable conditions. This seemed to be 

 true across a wide variety of species and locations: 

 wildebeest in Masailand (Talbot and Talbot 1963) and Kenya 

 (Croze et al. 1981), white-tailed deer in Texas (Teer et al . 

 1965), blesbok in South Africa (du Plessis 1972), African 

 buffalo in the Serengeti (Sinclair 1977), black bear in 

 Minnesota (Rogers 1987), mountain sheep in California 

 (Wehausen et al . , 1987), and mule deer in Montana. 



Talbot and Talbot (1963) reported that drought was the 

 primary factor controlling reproduction of wildebeest in 

 western Masailand. They stated (p. 71): 



"Low nutrition plane in wildebeests appears to be 

 caused by lack of green forage. Wildebeests in 

 western Masailand, being free to migrate widely 

 following rains, showed no evidence of low 

 nutrition. Wildebeests on the Athi-Kapiti plains, 

 however, being restricted throughout the year to 

 their former wet-season range, show evidence of low 



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