Black rat (Rattus rattus). Slightly smaller and more slender than the brown rat (Rattus norvegicus), it also has a longer tail, a pointier nose and larger ears. It was spread around the world by Europeans, but has now largely been replaced (at least in colder and more urban areas) by the heavier, more aggressive brown rat who also tends to have more babies. Brown rats are also burrowing animals while black rats are arboreal. They are still considered of least concern in the wild.
Similar to cleanliness, animals and insects can result in injury too. A hotel or restaurant must take care of any animal or insect that is in the vicinity to prevent negligence. Animals can bit or scratch customers which causes the company to be liable. Companies must routinely check their vicinity to keep animals and insects off the premises and away from customers.