nullcline

The 'th nullcline is the geometric shape for which .

The dynamics of this system can be nicely described by zapping between the left and right branch of the cubic nullcline.

In many of these problems, the solution satisfies the condition that the solution curve should cross transversally the nullcline or some other curve describing terminal conditions.

If we look at the nullcline for the larger animals (70kg, thick dashed line) we see that as the number of smaller animals is decreased the number of larger animals declines.