Deer growth is dependent upon weight, caloric intake, and energy expended during maintenance, travel, grazing, and reproduction. If energy intake from foraging is greater than energy expenditure, the deer gains weight, and if energy intake is less than energy expenditure, the deer loses weight [CGF+95].
Deer mortality is the result of several factors. Death by weight loss occurs if the deer's weight drops below 70% of its maximum weight ever attained [FDG+94]. Death by natural age-related factors occurs if the natural mortality rate for the deer's age is greater than a randomly generated number. Since panther are not simulated, death by panther predation is determined randomly, in order to maintain the deer population at somewhat realistic levels. Fawn mortality, in addition to the three factors described above, occurs if the mother dies while the fawn is still nursing.
Figure 3: SIMPDEL program flow by major subroutine