Kits born dead?!

[Avis]

I was playing as a fox just now and was about to give birth to 5 kits, I kinda glitch mated and gave birth to them in Spring? I didn't quite check. Anywhoo I gave birth and 4 of them were carcasses and only one survived! is this a glitch or something? Thanks

Edit; I just wanted to say I gave birth to them in the log at the very north of the forest, without a nest. Could that have caused it? it was in world 1 too.

[Alexander]

Not making a nest as a fox will definitely kill your kits.

[Scarikas]

Animals that need nests have to build a nest and have their kits on them, or else every kit except one will die. Can't avoid that :/

[Alrai]

Having offspring survive is the main incentive to building a nest. Animals desire mates with whom they will produce healthy and strong offspring, which is why building a nest is necessary before finding a mate in-game. c:

[StarWolf]

From my own experience, the nest needs to be at least 80% for all the young to survive. Of course, I've still had some babies die even at 80%... but usually only one.
Your nest doesn't necessarily need 100% of each item, either- as long as the nest looks complete, the game seems to take it as 'complete'. As a bluebird, I've had a nest made solely out of straw and still all the young survived.