I've noticed a lot of babies dying when it gets below 40 . . . the pinks have no hair to keep them warm, and even in the nests the females make, when the mom leaves to eat/drink, they are exposed. I've got mine in a shed now with a heater run into it on an extension cord. Lots more babies now--I actually have 12 pinks at the moment! LOL (It's been a while since I've had that many between feeding some off and losing some due to cooler weather.)