Hello. My boyfriend's chinchilla, fluffy, died this morning and we just don 't understand the reason. She was our first and beloved chinchilla. We got her with her son and 2-3 months later we took their old cagemate too, so that they were all together again.. they were really healthy and happy, until 2 weeks ago, when fluffy wasn't herself anymore. She couldn't breathe well, she was not eating drinking or pooping, neither running or hopping as she was before. We thought she was pregnant, my boyfriend told the vet the symptoms and she said she was probably pregnant but it could be dangerous for the labor to make x -rays to see if she was pregnant or not, so we just waited until one day that she wasn't well at all. We took her to the vet and she said fluffy wasn't pregnant, she had pneumonia. We started antibiotics and special nutritional food . We pushed her to eat to keep her strong and alive and gave her water and after a while she was hungry and she asked for food by herself. We thought she was getting better and would stay alive. She started running and jumping again. Today morning my boyfriend found her dead in her house with her eyes open. The vet said it was heart attack. What could have caused heart attack? maybe the fact she wasn't with her cagemates? Did we do anything wrong? Will her cagemates sense her absence and get depressed?