This can be caused by a Calcium or Vitamin B deficiency. Cramps are mostly found in pregnant females with one of these deficiencies, especially a calcium deficiency. Symptoms will be seizures or tremors that can look like heat stroke. But if this happens in winter heat stroke is obviously out. There can also be other causes like stomach cramps. The correct diet will prevent this. Cuttlefish bones (like we use for birds) are a good source of calcium. Chinchillas will readily nibble on it. When we started breeding chinchillas this happened to us a few times but since we introduced Dalvencor’s Eco Bitez about two years ago we never experienced it again.