The maturing Chestburster sheds it skin like a snake as it grows. Each shedding of skin and increase of body mass may cause the alien to secrete or lose of some its acidic blood. Its exoskeleton hardens and grows darker while its cranium elongates, and it develops sharp claws and a spiked tail. This maturation process takes only a few hours. On Fiorina 161, the alien tends to move around on all fours and acts to ensure that the unborn Queen growing inside of Ripley is protected.