animals give birth – – N. Ramalakshmi A: The answer is a combination of how many eggs are released or ovulated and the survival strategies of the species. Many large mammals such as elephants, cows, and humans typically release one egg per cycle and are heavily committed to that one offspring.

Pregnancy is long, the baby is relatively large and the mother puts a lot of energy into raising it. (Twins are born when either two eggs are released or one embryo splits into two.

) Many dogs, cats, pigs, rodents, rabbits, etc. often release multiple eggs in a cycle, so multiple embryos can develop simultaneously.

Their uterus is also made to hold multiple fetuses. And their newborns are smaller, the pregnancies are shorter, and the strategy is to produce many because not all will survive.

Tigers take a middle path: they usually have up to four cubs because their survival in the wild is uncertain, yet they invest heavily in each cub. They do not usually have large litters like dogs because raising each cub is still ‘expensive’ and requires a lot of milk and protection.