If F = {foxes}, R = {rabbits} then: / R &gt; / F &gt; \ R &gt; \ F &gt; / R &gt; ... which is shorthand for &quot;an increase in the number of rabbits leads to an increase in the number of foxes (since they have more to eat), but an increase in the number of foxes acts to decrease the number of rabbits (since they are eaten);
(they; are eaten; ) (they; have; more to eat) (more; to eat; )
they they more
are eaten have to eat
more to eat