When it is not guaranteed for offspring to survive until adulthood, one strategy that many organisms have adopted is known as r-selection. In r-selection (or r-strategist organisms), the organism has numerous offspring that don’t require a lot of energy to raise. And since it is unlikely for the majority of the offspring to survive, it is not a tremendous loss when the offspring die because a minimal amount of energy has been expended into raising the young. Also, since the amount of offspring is so large, when some of them die, there are still others that will live to pass on the genes and contribute to the gene pool.
Some characteristics of r-strategists include: a short life-expectancy, early maturity, low energy requirements to raise young, and giving birth to many offspring at the same time. The rabbit shown in the picture is an example of an r-strategist. Female rabbits, known as does, have a pregnancy time of 31 days. In one pregnancy, the doe can give birth to multiple young- anywhere from 1-12 young at a time. Not only is the doe capable of giving birth to many young at a time but she can become pregnant again just days after she has given birth!