Armadillos are unusual creatures, the only mammals whose body is almost completely covered with a dense shell. And yet, these unique animals are known as masters for family planning.

If a pregnant female encounters severe environmental stress, she can halt the development of her embryo for a period of several months to two years and then allow it to resume when conditions improve.

Armadillos are the only mammals in the world with this extraordinary ability. And one of the rare animals, along with some types of kangaroos and wallabies, that can manage the timing of their pregnancy.

Scientists have found that the suspension of embryonic development occurs at a very early stage - the blastocyst - when the embryo is nothing more than a tiny ball of cells, ready to penetrate the uterine wall. Presumably, this is influenced by the hormonal effect of stress, as well as reduced metabolism and body temperature of this animal. A fertilized egg goes through only the initial stages of development, then this process stops and can remain in the dormant stage for up to two years.

Interestingly, when pregnancy resumes, a female armadillo can give birth one to four cubs of the same sex - all either boys or girls.