How do they know?

I used to have a seizure alert dog. They can smell the changes in body chemicals that are let off on the skin - that's what I was told by the lady that trained my dog for me. It is by that and the subtle changes in the body/facial expressions. These are things that humans don't really know enough to watch out for. If you learn to watch animals, you learn things. The Natives have been doing it for many years and people always thought they were crazy.

Infact every creature of GOD has unique qualities. He has distributed the creation and have assigned them their work for which they are given some special senses. It's actually these senses which help them foretell about a possible coming situation. Like you quoted some examples. similarly birds get off from trees usually in the event of earthquake. but all these things have scientific explanations. There sensory organs sense the coming danger to avoid it. they feel the changes in environment, normal physical behavior, and signs and symptoms to get a feeling of upcoming things. experience and training of the species also count in this regard and humans have certain abilities too, that may get un noticed in daily life. For example, a mother can foretell what the baby is going to do in most of the situations because of her earlier experience of the symptoms that appear on baby's face or body. But i admit that animals have more senses developed perhaps in these fields than humans. It's just the functions of the sensing abilities that they already have and use.