that "Carrying capacity changes from season to season on the 

 same range." This complexity and the variable nature of 

 carrying capacity was also pointed out by Edwards and Fowle 

 (1955) when they stated: "The really important thing is to 

 recognize that carrying capacity is not a stable property of 

 a unit of environment but the expression of the interaction of 

 the organisms concerned and their environment. Moreover, the 

 carrying capacity of an ecosystem may fluctuate in response to 

 the ebb and flow of interactions going on within it." 

 Sinclair (1981) similarly noted "A population at carrying 

 capacity should not be thought of as one with a stable or 

 constant level. Rather, it is one that is fluctuating, often 

 extensively, between certain boundaries." Hobbs et al . (1982) 

 have empirically shown extensive annual fluctuations in 

 energy-and nitrogen-based estimates of carrying capacity for 

 elk (Cervus elaphus nelsoni) winter range. 



Following the concept that carrying capacity reflects the 

 availability of forage resources and forage-animal 

 interactions, different definitions and terminology have been 

 proposed or applied, based on the management objectives for a 

 given population. The maximum or equilibrium number of 

 animals that can be supported under natural conditions (in a 

 non-hunted area) has been variously termed subsistence density 

 (Dasmann 1981), environmental carrying capacity (Clark 1976), 

 K carrying capacity (McCullough 1979), potential carrying 

 capacity (Riney 1982), and ecological carrying capacity 

 (Caughley 1979). By definition, the rate of increase of both 

 plants and herbivores at K carrying capacity is zero (Macnab 

 1985). "Equilibrium" is reached through a sequence of 

 increased juvenile mortality, increased age of sexual 

 maturity, decreased birth rate among adults, and increased 

 adult mortality (Macnab 1985). 



For managed populations in which harvesting occurs, 

 following the concept of maximum sustained yield (MSY) , other 

 definitions and terminology have been proposed and applied to 

 "carrying capacity. " This position on the continuum of 

 possible ungulate/vegetation densities (Macnab 1985) has been 

 called optimum density (Dasmann 1981), "I " carrying capacity 

 (McCullough 1979), and economic carrying capacity (Caughley 

 1979). It assumes a lower standing crop of ungulates and a 

 higher standing crop of vegetation (a lower practical or 

 realized carrying capacity) than K carrying capacity. Also 

 inherent is the assumption that with a higher standing crop of 

 forage, the animals are more productive and a higher annual 

 yield or harvest is available (MSY) . 



