The veterinarians felt that the loss of her litter had caused the tigress to fall into a depression. The doctors decided that if the tigress could surrogate another mother's cubs, perhaps she would improve. After checking with many other zoos across the country, the depressing news was that there were no tiger cubs of the right age to introduce to the mourning mother..
This site tells you when is best to get up or fall asleep according to when you are going to bed or have to get up. It is based of off sleep cycles not time. if you wake up in the middle of a sleep cycle you will most likely feel more tired throughout the day than if you woke up at the end of one! worth a try only takes a second!