African penguin embryos rely entirely on the contents of the egg to develop. The yolk has the required sugars, fats and cholesterol. The extensive blood vessels that are found throughout the egg move the nutrients to the embryo. After only 10-14 days the embryo is easy to recognize; the eyes are very large early on. Tail feathers are seen early in the second trimester. Oxygen and carbon dioxide are transported through microscopic pores in the egg shell. The egg shell forms a high proportion of the egg weight which may be related to the fact that many penguin species utilize very little nest material. By Day 32-35 the chick is so large in the egg that an egg candler only shows a very dark, full embryo. In order for the staff to determine viability of the embryo we utilize a digital heart rate monitor called an Egg Buddy. The Buddy shows the chick’s heart rate in BPM (Beats Per Minute).-Pamela Schaller

African penguins incubate eggs by covering them with a brood patch. This is a patch of skin that lacks feathers and becomes infused with blood. When a penguin is standing it is not easy to recognize this patch. However, in the photo above the male penguin has not yet developed his brood patch and the female has already. Often , the female develops her brood patch in conjunction with egg laying. In the penguin with the band on her left wing, you can see a slightly swollen “line” in the center of her belly going to in between her feet. When incubating eggs, whether it is the male or the female, the penguin stands over the egg, stretches its brood patch over the eggs and lays down on top of them. Because they cannot completely cover the egg, they also often stand enough to rotate the eggs then lay on top of them again. The eggs must remain at about 97-98 degrees Fahrenheit for 37-38 days in order for chicks to hatch out. -Pamela Schaller