into his nest. Males are simultaneously polygynous, females are serially polyandrous. In practice, this means that the females move around during breeding season, mating with a male and depositing their eggs with the male before leaving him and mating with another male. Males on the other hand are sedentary, attending the nests and taking care of incubation and the hatchlings all on their own. Recent evidence has shown that some males will utilize subordinate males to help incubate and protect the eggs. If this happens, the dominant male will find a second harem and start the process over again. The nests are thus collectively used by several females and can contain as many as 80 eggs laid by a dozen females; each individual female's clutch numbers some 5–10 eggs. However, the average clutch size is 26 eggs laid by 7 different females. Rhea eggs measure about and weigh on average; they are thus less than half the size of an ostrich egg. Their shell is greenish-yellow when fresh but soon fades to dull cream when exposed to light. The nest is a simple shallow and wide scrape in a hidden location; males will drag sticks, grass, and leaves in the area surrounding the nest so it resembles a firebreak as wide as their neck can reach. The incubation period is 29–43 days. All the eggs hatch within 36 hours of each other even though the eggs in one nest were laid perhaps as much as two weeks apart. As it seems, when the first young are ready to hatch they start a call resembling a pop-bottle rocket or even fireworks, even while still inside the egg, thus the hatching time is coordinated. Greater rheas are half-grown about three months after hatching, and sexually mature by their 14th month. Predators The natural predators of adult greater rheas are limited to the cougar (Puma concolor), which are found in most areas inhabited by greater rheas and are certain to be their leading predator, and the jaguar (Panthera onca), which are found with greater rheas and opportunistically hunt them in the Paraguayan chaco, central Bolivia and the Brazilian cerrado. Feral dogs are known to kill younger birds, and the crested caracara (Caracara plancus) is suspected to prey on hatchlings. Armadillos sometimes feed on greater rhea eggs; nests have been found which had been undermined by a six-banded armadillo (Euphractus sexcinctus) or a big