When my husband was diagnosed with lung cancer, it occurred to us that his Jack Russell Terrier had been laying with his head on Alvin's chest every time he sat with him for the past several months. He had never done that in all the years he had him. We felt that Jack either smelled the cancer or sensed it. As strange as it sounds, Jack was diagnosed with cancer 11 months after my husband. Jack's spleen ruptured and caused internal bleeding 2 weeks after diagnosis. We had to put him down. Alvin passed away 2 months later.