A certain species of desert lizard digs tunnels in which to lay its eggs  The eggs must incubate inside the tunnel for several weeks before hatching, and they fail to hatch if they are disturbed at any time during this incubation period
Yet these lizards guard their tunnels for only a few days after laying their eggs
Each female lizard lays from 15 to 20 eggs, only about 10 of which hatch even if the eggs are not disturbed at any time during the incubation period.