Kangaroos and wallabies, closely related marsupials, have unique reproductive characteristics. Their gestation periods vary depending on the species, with the largest species, the red kangaroo, having a pregnancy of around 36 days, while smaller species like the parma wallaby have a gestation of 19-22 days. This relatively short gestation period allows for multiple births throughout the year and contributes to the survival of these animals in their often harsh and unpredictable environments.