The brown rat is a relatively large domestic mouse in the family Muridae. The body is thick and sturdy, with a tail that is more than one-third of the body length, sparse fur, and clearly visible circular scales. The head is small and the kiss is short, the ears are short and thick, and they cannot be rolled forward to reach the eyes. The hind legs are relatively thick. There are 6 pairs of nipples, 1 pair of abdomen, and 3 pairs of groin in female brown rats. The body back hair is mostly brown or gray brown in color, with a dark gray base and brown dyed tips. The head and back center of the hair are darker in color, and some parts are all black with long hair. The lateral hair color is slightly light, the base of the ventral hair is dark gray, the tips of the hair are light gray, and it is slightly stained yellow. The squamous segment of the tail is present, and the fur of young mice is darker, dark brown, and relatively soft. The body hair varies depending on age and habitat.



The skull is thick and the orbital ridge is well-developed, connected to the temporal ridge and extending backwards to the squamous bone. The temporal ridges on both sides are almost parallel. The width of the parietal bone is almost equal to the width of the left and right parietal bones, which is one of the obvious characteristics that distinguish brown rats. The upper molars have three longitudinal dental processes, with a length of 7-8mm. There are no well-developed dental processes behind the first and second upper molars, and the chewing surface of the molars presents three transverse ridges.



2、 Yellow breasted rat



The yellow breasted mouse is a larger mouse in the family Muridae, similar in size to the brown rat, with a slender body and a tail that is thinner and longer than the brown rat, exceeding its body length. Body length 130-150mm, weight 75-200g, tail length equal to or greater than body length. The ears are long and thin, and pulling them forward can cover the eyes. The hind foot is slender and longer than 30mm.

5 pairs of female nipples, 2 pairs of breasts, and 3 pairs of abdomen. The back of the body is brown in color, mixed with black, and the fur base is dark gray. There is a clear dark gray brown spot in the center of the forefoot back, which is an important morphological feature for distinguishing the yellow breasted mouse, especially in the south, from the yellow haired mouse. The tail scales are well-developed, circular in shape, and have long fine hairs.

The skull is smaller than that of brown rats, the snout is shorter, the incisors are larger, the nasal bone is longer, and the orbital ridge is well-developed. The anterior edge of the crown of the first upper molar has a band like protrusion, and there are three transverse ridges on the chewing surface of the molar. The first row of transverse ridges on the chewing surface of the second and third upper molars has degenerated, leaving only one inner tooth protrusion. The second and third transverse ridges are clearly visible along the edge of the second upper molar, while the third upper molar has already healed, forming a "C" shape.



3、 Little house mouse



The house mouse is small in size, with a body length of 60-100mm, a tail length shorter than or equal to body length, and a weight of 9-20g. The head is small, the kiss is short, the ears are round, about 11-14mm, and the fur is clearly exposed. The limbs are slender and weak, with a short hind foot that is only slightly longer than the ear length, less than 19mm.



Five pairs of female mouse nipples. The fur color varies greatly with seasons and environments. The back hair is brownish gray, gray brown or dark brown, the base of the hair is black, and the ventral surface is white, gray white or white yellow;



The tail has two colors, with a darker back that is dark brown and a slightly lighter belly that is sandy yellow. The back of the four feet is dark brown or dirty white.

The skull is slightly slender, the snout is short, the skull is low and flat, and the frontal bone is slightly arched upwards. The incisor hole is relatively long, with its posterior edge exceeding the connecting line of the anterior edge of the first upper molar. No orbital ridge and temporal ridge. The sound is small and relatively flat. The posterior edge of the maxillary incisors has a very obvious notch, which is the main characteristic for its classification and identification. The maxillary incisor chewing mask has three longitudinal arch shaped dental processes. The first molar is very large, and its crown length is approximately equal to the sum of the crowns of the second and third upper molars.