Hi Matt,
First, I'd like to say that I am very sorry this happened. Usually, when kittens are this age, and have been doing well, there are no problems at all.
The only time I personally have seen this kind of thing was with a newborn kitten. In this case, what probably happened is that the mother cat, while chewing the cord, kept on going and ate part of her kitten. This is more likely to happen with inexperienced cat moms.
It's hard to imagine a mother cat eating a 5 week old kitten, though. It's more likely that another animal got to the baby when he or she was away from the others. Sometimes, if a mother cat senses that a kitten is ill, she will remove the kitten from the others. The instinct to protect her healthy offspring is very strong. If another animal had access to where this poor baby was found, I would suspect he or she killed it.
Perhaps the mom was found eating part of the kitten as a way to protect the others as well, to keep what she considers prey away.
Or maybe, in her own way, she was trying to "revive" the deceased kitten. It's so hard to say for sure.
Please watch the mom and remaining babies very closely. If she is the cause of the kitten dying, she may try to hurt the others.
Hope this has helped some.
Take care,
PHKitkat
