The most common rodent in Hong Kong can be classified as Rattus norvegicus , Rattus flavipectus and Mus musculus . They are sociable mammal. Although they have poor eyesight, but the sense of smell, touch and hearing are very sensitive, with good memory, they can recognize direction easily. They are also strong in reproduction, normally one birth can have eight to ten babies, which can produce more than fifty in one year. Female can mate immediately after giving birth. In general they are athletes, swimmer and climber. Is there nothing we can deal with them? The answer is no, because human is the most clever mammals in the world.

Mus musculus	Rattus norvegicus is active on top of ceiling. They appear mostly in restaurant and café.	The incisor of Mus musculus	Their excerment

Harm:

	Spread disease- including plague, urban typhus, Hantaan fever and Boutonneuse fever.
	Economic loss- they destroy household articles, short circuit of electricity and disconnection of telephone line when bite off the cables.
	Attack human- they might attack anyone around you.
	Track- beware of rodent if excrement, holes, tooth track or footmark are found.

Methods of prevention:

	Cut water and food- store food properly; close all the water taps tightly.
	Cut their place to hide- do not leave any chance for them to build their house, the most important is having good sanitation.
	Gap enclosure- close all the gaps which are possible for them to enter the house.
	Apply poison- apply poison in suitable place and to trap them.