Since the model deals only with total female population size, the total
birthrate is divided by 2. Death of infants from natural causes is a function of
Int_Infant_Death_Rate, which we assume to be 4 %, and the actions of an infanticidal male. The latter is estimated from the literature to be 0.366 [2].
To calculate the total adult female population size in our model, we could have
created a converter and connected into it with action connectors the stocks of fertile,
pregnant, and lactating individuals. Instead, we made use here of STELLA’s
Summing Converter (shown in Fig. 14.4 and used in the lower left-hand side of
Fig. 14.1). You can select the Summing Converter by clicking and holding the
Converter tool on the toolbar and place it anywhere in your model. Upon opening it,
you simply need to specify which model components should be summed up, and
STELLA does the rest.
Figure 14.5 shows how often males are replaced and that the modeled tenure
lengths fit well with the known average and range. The total female population size
is shown for four runs in Fig. 14.6—first without infanticide and for subsequent
runs with (randomly) occurring infanticides, assuming 50 % of males to be infanticidal. Figure 14.7 compares total female population sizes for three different
percentages of infanticidal males—0, 50, and 100 %.
Fig. 14.4
Fig. 14.5
14.1 Langur Infanticide Model
125
birthrate is divided by 2. Death of infants from natural causes is a function of
Int_Infant_Death_Rate, which we assume to be 4 %, and the actions of an infanticidal male. The latter is estimated from the literature to be 0.366 [2].
To calculate the total adult female population size in our model, we could have
created a converter and connected into it with action connectors the stocks of fertile,
pregnant, and lactating individuals. Instead, we made use here of STELLA’s
Summing Converter (shown in Fig. 14.4 and used in the lower left-hand side of
Fig. 14.1). You can select the Summing Converter by clicking and holding the
Converter tool on the toolbar and place it anywhere in your model. Upon opening it,
you simply need to specify which model components should be summed up, and
STELLA does the rest.
Figure 14.5 shows how often males are replaced and that the modeled tenure
lengths fit well with the known average and range. The total female population size
is shown for four runs in Fig. 14.6—first without infanticide and for subsequent
runs with (randomly) occurring infanticides, assuming 50 % of males to be infanticidal. Figure 14.7 compares total female population sizes for three different
percentages of infanticidal males—0, 50, and 100 %.
Fig. 14.4
Fig. 14.5
14.1 Langur Infanticide Model
125