Rats are rodents, and are quite intelligent. The creatures themselves are rarely seen, even in the areas they inhabit, and can be identified by their byproducts. Their droppings can be found in the home, and they can be heard making noise right after dark. The two most common types in California are the Norway Rat and the Roof Rat. Norway Rats are slightly larger, while Roof Rats' tails are longer than the length of their head and body combined.
Rats can present a number of health and safety dangers. Contamination does occur to both human and pet foods in homes invaded by rats. It is best to dispose of rat carcasses with disposable rubber gloves and a properly fitted HEPA mask. Both common species of rat can chisel through wires and structures with their front teeth. Rats are carriers of many diseases themselves, such as typhus and plague. They are also transporters of parasites such as fleas and ticks that have their own dangers.
Once rats have found shelter in a residence, they are quite hard to remove. It is best to deal with a rat problem preemptively, before their numbers have gotten very high.They can be found living in places such as your woodpile, and their nests can be made of things such as scraps of paper or cloth. And their carcasses may be found on your property, or been killed by a pet.