Do Quokkas Actually Throw Their Babies At Predators?
This question started as an online joke, and as time went on, people started taking it seriously. The answer to the question isn’t that simple, however. Firstly, it should be noted that no, quokkas don’t throw their babies at predators. That is a joke, but it is somewhat based on reality. Quokkas keep their young in their pouches, and while fleeing from predators, babies are known to fall out and are then left there by their parents.
The thing that is interesting here is that the part where they fall out of the pouch may be done on purpose by the mothers. Research shows that this may be an actual anti-predator characteristic of quokkas. They normally have very strong control over the muscles in their pouches, so their response to the threat of predators may be to release those muscles. The babies are left there to attract the attention of the predator, and the parents can safely escape. Mothers want to save themselves because they have proven that they are fertile, while the young might not be.
The effect that would be “canonized” or fixed would be the relaxation of the pouch. If dropping kids had a negative reproductive effect, the pouch would stop going slack eventually. If it had a positive effect, the pouch would relax more readily, so it wasn’t an occasional accident but a common strategy.
My point is that something that has such a direct effect on reproduction is never going to get “ignored” by selection.
If the relaxation of the pouch is directly tied to the stress/adrenaline response diverting resources elsewhere, which aids in escape, then it’s not so easy to optimize to not loose the pouch. Pouch relaxation wouldn’t be the genetic trait being selected for or against, flight response would be.
It can be more harmful for the pouch to be relaxed than not on an isolated level, but if that’s counteracted by the increased ability to escape due to resource allocation then it would pass on as a “by product” regardless of its individual effect.
There may not be an existing genetic variation which maintains the pouch control during the flight response without compromise on the degree of speed or intensity dedicated to the escape. Evolution can’t select for mutations that don’t yet exist in the gene pool.