Some of the youngest animal moms are so young when they reproduce that they are practically born pregnant.
Humans and other primates can take years to reach sexual maturity—the age at which we develop enough to be able to reproduce. Not all animals are like us, however; some begin reproducing at a very young age. Here are some of the animal world's youngest parents.
A young cottontail waits for food [Photo by Jessie Eastland - Own work, CC BY-SA 4.0]
Rabbits are famous for multiplying like they're getting paid for it. Cottontails in particular are quite prolific for a very good reason—they reach sexual maturity at just two to three months old. Add to that the fact that cottontails take only a month to gestate, and you can do the math from there.
However, that's not all. Female cottontails only need about a day to get ready to breed again. Thus, females can get pregnant again just a day after giving birth.
There may be a reason that cottontails mature at a relatively young age. Their lifespans are also relatively short—just about two years on average. Plus, newborn cottontails are practically defenseless against predators, and very few make it to adulthood.
An addax and her young
Humans can actually begin reproducing pretty young, but just because we can doesn't mean we would or should. Most of us have been socialized to find reproducing at a later age more acceptable than reproducing quite young. The addax is also able to reproduce quite young—about 10 months old—but social pressures postpone successful reproduction until the addax is at least three years of age.
In the case of the addax, these social pressures involve dominance among males. When dominant adult males begin to establish their territories, they need to keep younger males from reproducing. Thus, addax antelopes can begin breeding at a younger age, but are more successful when they're older.
An aphid giving birth to live young [Photo by MedievalRich at the English language Wikipedia, CC BY-SA 3.0]
Aphids are tiny, common pests that suck the sap out of plants. According to St. Louis Zoo invertebrates creator Ed Spevak, these insects are “essentially born pregnant”. When a female aphid hatches from her own egg, she already has eggs growing inside of her. Aphids reproduce asexually, which means they're basically just cloning themselves when they reproduce.
If aphids reproduce asexually, then what's the use of the species having males and females? Interestingly, aphids will resort to sexual reproduction when their species is threatened. If, for example, their environment becomes unstable, they need to produce stronger offspring. This means diversifying their gene pool, making sexual reproduction necessary.
Get weekly science updates in your inbox!