 It is carried out blindly using only the hind legs to dig a -deep cylindrical hole, in which the tortoise then lays up to 16 spherical, hard-shelled eggs ranging from in mass, and the size of a billiard ball.Some observations suggest that the average clutch size for domed populations (9.6 per clutch for "C. porteri" on Santa Cruz) is larger than that of saddlebacks (4.6 per clutch for "C. duncanensis" on Pinzón).The female makes a muddy plug for the nest hole out of soil mixed with urine, seals the nest by pressing down firmly with her plastron, and leaves them to be incubated by the sun.