1. Can you think of
any examples of other systems that demonstrate the kind of behavior that we
found in the predator-prey model?
Parasite-host dynamics are likely similar, where parasite
population increases until the host’s capacity is reduced, at which point the
parasite population declines until it finds a new host or the original host
recovers to the point where the parasite can again expand.
2. In some
predator-prey systems the prey can take refuge to hide from predators and avoid
being consumed. Usually there is only a certain fixed number of individuals
that the refuge can house. When the population of prey is large there is not
enough refuge for all and the prey that could not find a place to hide gets
consumed like in the standard predator-prey formalism. However when there are
just a few preys their consumption slows down because they can find enough
refuge places to hide. Build a predator-prey model with refuge and describe the
dynamics that you observe. What equations did you modify and how? How can you
explain the effect of refuge on the overall system dynamics?
To accomplish this, I made predation an exponential
function:
V = y*a*eb*x
Where V is predation, y is # wolves, x is # rabbits, and a
and b are parameters that represent, respectively, the magnitude of the refuge
available to the rabbits and how easily rabbits beyond the refuge are taken by
wolves.
In general, this has the effect of stabilizing the system’s
equilibrium. Effectively, the rabbit population is limited to the size of the
refuge and the wolf population consequently limited by the size of the rabbit
population. This causality can be seen reflected in the fact that the wolves’
curve reaches its asymptote slightly later than the rabbits’ curve.
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