Could these traits have evolved little by little?
“Since females give birth hanging upside down high above the ground, there is a serious danger of the newborns falling to the ground and dying. Therefore, oftentimes one or two other females spread their wings underneath the delivering mother, ready to catch the little one if needed. God has also given bats other incredible traits. Some hibernating bats mate in the autumn, but the sperm remains dormant in the female as she goes into the hibernating state (a drastic reduction of the metabolic rate, with heartbeat and breathing slowing dramatically, and body temperature equalizing with the environment). Once she returns to active life in spring, the fertilization takes place. In some other hibernating bats, fertilization takes place immediately after mating but then the fertilized egg stops developing until the end of hibernation. Both these unusual characteristics have the same purpose: to ensure that birth occurs at the right moment so that the newborns have enough time to grow sufficiently strong to survive their first hibernation. One cannot but stop and wonder at how evolutionary mechanisms would generate such massive qualitative changes in the reproductive cycle of these creatures. A designed solution seems by far the best interpretation.” (Emil Silvestru, The Cave Book, Master Books, Green Forest, AR, 2008, p 24.)
Find that book here: http://www.discovercreation.org/shop/youth-adult-books/the-cave-book/