What is considered a rat? - briefly
A rat is a medium‑sized, omnivorous rodent of the genus Rattus, identified by a pointed snout, continuously growing incisors and a long, hairless tail. Common species, such as the black rat (R. norvegicus) and the brown rat (R. rattus), inhabit urban and rural areas worldwide.
What is considered a rat? - in detail
A rat is a member of the genus Rattus within the family Muridae, order Rodentia. Taxonomic classification places it among mammals characterized by continuously growing incisors that must be worn down by gnawing. The two species most frequently encountered worldwide are the brown rat (Rattus norvegicus) and the black rat (Rattus rattus), each exhibiting distinct morphological and ecological traits.
Physical characteristics include a robust body, a relatively long tail that is nearly equal in length to the torso, and a pointed snout. Fur coloration varies from brownish‑gray in R. norvegicus to dark brown or black in R. rattus. Adult weight ranges from 150 g to 500 g, with females typically lighter than males. The skull possesses a high nasal bone and a well‑developed auditory bulla, adaptations that support acute hearing and olfaction.
Behavioral criteria that identify an animal as a rat involve:
- Nocturnal activity: peak foraging occurs during night hours.
- Omnivorous diet: consumption of grains, fruits, insects, carrion, and human waste.
- Social structure: formation of hierarchical colonies with defined breeding pairs.
- Reproductive capacity: gestation lasting 21–23 days, litter sizes of 6–12 offspring, and the ability to produce multiple litters annually.
Legal and regulatory frameworks often define a rat for pest‑control purposes based on these biological markers. For instance, many jurisdictions classify any rodent of the Rattus genus that exceeds 100 mm in body length (excluding the tail) and displays the above traits as a target for eradication programs.
In summary, classification as a rat hinges on taxonomic placement in Rattus, specific anatomical features such as tail proportion and dental structure, and characteristic nocturnal, omnivorous, and social behaviors. These criteria collectively distinguish rats from other rodents and inform scientific, medical, and regulatory contexts.