Cloning remains an unpredictable process. A study by the Whitehead Institute for Biomedical Research shows that fewer than 10 percent of cloned embryos survive to birth. Those that make it are often born oversize and die earlier than normal. The animals listed here represent a sample of the roughly 15 cloned species.

Sheep (“Dolly”)

7/1996

Died of lung

disease at 6 1/2

Healthy

Bull

8/1999

Chinese Goat

6/2000

Died in one day

(abnormal lung development)

Gaur, or wild ox

1/2003

Died in two days

(from poor diet)

Banteng, or Asian wild ox

4/2003

Born twice

normal size; euthanized

Healthy

African wildcat

4/2003

Healthy

Mule

5/2003

Healthy

Horse

5/2003

Healthy

Deer

5/2003

Rats

9/2003

One died soon

after birth; two are healthy