Predator – Prey Dynamics and the Red Queen Hypothesis
Fig . 2 . Population and average age changes as predators ' " turns per tick " is reduced by onethird . Predator population ( left ) and average age ( right ) are in purple ; prey are in red , and food is in green ( left only )
Fig . 3 . Population and average age changes as predators ' " success rate " is reduced by onethird . Predator population ( left ) and average age ( right ) are in purple ; prey are in red , and food is in green ( left only )
situation , however , we find quite a different result . The predator population does not decrease at all for being less effective hunters , but this does allow the prey population to increase , by approximately one third , and the prey average age also increases by a similar amount ( Figure 3 ). The predator consumption rate is unchanged , but the prey consume food approximately one third less often which , perhaps paradoxically , reduces the total available food in the system ( but by approximately one half ).
The first case above can be interpreted as a slowdown in the metabolism of all the individual predators ; their lifetime is longer relative to the prey , but they do not consume any more prey across that lifetime . It is as if they have more resources available during a simulation time step , and therefore the predator population numbers benefit from this effect . The second case shows that even if all the predators become less effective hunters , by missing their prey one third of the time , their total population does not suffer in any way . Conversely , if the predators improve their hunting success , the prey suffers both individually and collectively , living a shorter lifespan and displaying a concurrent drop in total population size . If left unchecked continued , predation improvements would conceivably drive the prey to extinction . Therefore , the next set of experiments considers what mechanism is sufficient to prevent this outcome .
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