Biology Reference
In-Depth Information
Create environment
Initialize populations
Calculate mortality for all agents
Move hosts across environment
Check for ticks finding hosts
Update scent variables
(RMSF-SIM only)
Update tick activity status
Calculate changes in infectious
status for ticks and hosts
Check for recovery of hosts
FIGURE 4.9
Flow diagram for TICKSIM and RMSF-SIM models.
characteristics of itself and not the ecosystem being unable to supply due to its own
inherent breakdown or unrealistic overabundance of a resource.
4.4.5
Design Concepts
The tick agents in both models can sense hosts to use for blood meals but still only
have a small probability of actually successfully attaching to that host. The density
dependence for ticks is only indirectly implemented by giving a maximum number
of ticks per host as assigned for each host species.
In TICKSIM, the hosts simply move randomly around the uniform grid of patches.
In RMSF-SIM, the forest patches serve as home for host agents but has no food. The
grassland has a variable amount of food available depending on the time in the year
and the consumption by prey agents. The system for both models is closed.
In RMSF-SIM, there is an additional layer of interactions for a predator-prey rela-
tionship between the two host species. The ABM tracks three variables that govern
each host's activities: age, energy, safety. The probability of death from other envi-
ronmental causes increases as a function of age for both predators and prey. Both
predators and prey must maintain a set energy level to prevent starvation. Energy
is lost over time and through movement, and is gained through food. Safety is a
measure of time spent away from the home area in the forest. All host agents have
to navigate back to their home area on a regular basis. Host agents are kept at a constant
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