Name the defence in each case. A frog that is the same colour as the leaf on which it sits…

In predation, the predator gains and the prey is harmed. Predators carry energy, control the prey and keep species diversity. Prey defend with camouflage, poison and warning colours, thorns and chemicals. The balance point of the Lotka-Volterra equations $\dfrac{dx}{dt} = ax - bxy$ and $\dfrac{dy}{dt} = cxy - dy$ is $x = d/c$ and $y = a/b$, and the swings have the period $2\pi/\sqrt{ad}$.