Rattus norvegicus (2) Brown Rat Mouse Skull Mammalia Rodentia Muridae

Brown Rat Mouse Skull Rattus norvegicus cm 4.1 Mammalia Rodentia Muridae, complete of mandible, only a piece, as in photos.
Family: Muridae (mice).
Common name: Brown Rat, Common Rat, Street Rat, Sewer Rat, Wharf Rat, Hanover Rat, Norway Rat or Norwegian Rat.
Syn. Rattus caraco, Rattus caspius, Rattus decimallus.

The Brown Rat (Rattus norvegicus, Berkenhout) is a rodent mammal of the Muridae family.
It is the most common and widespread species of Rattus, present practically throughout the world; in Europe it supplanted the pre-existing black rat (R. rattus) between the end of the Middle Ages and the industrial revolution. Despite its scientific name, the Norway rat originates from Asia. Five subspecies are known, the validity of which has however often been questioned. The name norvegicus dates back to 1769, when the naturalist John Berkenhout recounted the arrival of rats in England via ships of Norwegian origin. In nature, the species is associated with permanent sources of even brackish water: however, it is a distinctly anthropophilic species, which prefers environments with strong and permanent anthropization, colonizing the sewers (hence the name "sewer rat", in as opposed to the roof rat which prefers dry areas), landfills and in general areas where there is a strong dispersion of food and poor hygiene. It can measure up to 40 cm, of which just under half belongs to the tail, for an average weight of 350 g up to a maximum of 1 kg. These animals are active mainly at night, while during the day they sleep in very complex nests placed in a ravine widened by digging with its front legs and teeth and made more comfortable with a padding of herbs and other material. Rats mostly live in groups made up of a progenitor pair and their numerous offspring, subordinate in size order. These are basically omnivorous animals, eating practically everything edible they can find. In the wild, the species tends to feed mostly on cereals, but they can also hunt small animals. Gray rats can reproduce throughout the year, producing on average 7 litters of 3 to 15 pups. The presence of the gray rat in Europe can be dated back to 1553; currently, the gray rat is the second most successful mammal in the world, after humans: it is believed that in large cities, such as New York or London, there are more rats than human inhabitants.
Skull: The temporal arches of the skull are straight rather than curved as in the gray rat and has two bony crests on the top of the skull, which are absent in the black rat. In the mouth there are sharp incisors covered with yellowish enamel.