Chapter 23
Roan Herds
We descended into a valley, bent upon the destruction of a roan
antelope.
(W. C. Harris, 1839)
23.1 Roan Herd Model
In the previous chapter we have captured environmental influences on population
dynamics through the concept of a carrying capacity, captured through the influence
on death rates from changes in available land and associated population density. As
parameters of the physical environment change, so does the carrying capacity of the
ecosystem. Let us model environmental influences in more detail and focus on
seasonal fluctuations and spatial differences in environmental parameters. We
develop the model of this chapter for roans.
The roan is an antelope-like animal in Africa. Our problem is to model its
population cycles given a weather-grass availability pattern (called KP and KM)
and two different habitats called “prime” and “marginal” ground. The converter KP
controls the birth and death rate of any roan that live on the prime ground; the
converter KM controls the same for those roans living on the marginal ground.
These converters are shown in Figs. 23.1 and 23.2.
For these converters, the variable YEAR is defined by
YEAR ¼ INT MOD TIME; 12
ð
Þ
ð
Þ þ 1
ð23:1Þ
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_23,
© Springer International Publishing Switzerland 2014
191
Roan Herds
We descended into a valley, bent upon the destruction of a roan
antelope.
(W. C. Harris, 1839)
23.1 Roan Herd Model
In the previous chapter we have captured environmental influences on population
dynamics through the concept of a carrying capacity, captured through the influence
on death rates from changes in available land and associated population density. As
parameters of the physical environment change, so does the carrying capacity of the
ecosystem. Let us model environmental influences in more detail and focus on
seasonal fluctuations and spatial differences in environmental parameters. We
develop the model of this chapter for roans.
The roan is an antelope-like animal in Africa. Our problem is to model its
population cycles given a weather-grass availability pattern (called KP and KM)
and two different habitats called “prime” and “marginal” ground. The converter KP
controls the birth and death rate of any roan that live on the prime ground; the
converter KM controls the same for those roans living on the marginal ground.
These converters are shown in Figs. 23.1 and 23.2.
For these converters, the variable YEAR is defined by
YEAR ¼ INT MOD TIME; 12
ð
Þ
ð
Þ þ 1
ð23:1Þ
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_23,
© Springer International Publishing Switzerland 2014
191