Who is a large rat? - briefly
A large rat denotes an adult Norway rat (Rattus norvegicus) that can attain a body length of about 30 cm and a weight of up to 500 g. These specimens are prevalent in cities and are frequently employed as model organisms in scientific research.
Who is a large rat? - in detail
A large rat refers to any rodent of the genus Rattus or related genera that reaches a body length of 30 cm or more, not including the tail. The most common examples are the brown rat (Rattus norvegicus) and the black rat (Rattus rattus) when individuals exceed typical dimensions.
Physical traits
- Head‑body length: 25–30 cm (average); exceptional specimens reach 35 cm.
- Tail length: equal to or slightly longer than the body, often 30 cm.
- Weight: 300–500 g for average adults; large individuals may exceed 700 g.
- Fur: coarse, brown to black, with a scaly tail lacking hair.
Habitat and distribution
- Urban environments: sewers, basements, warehouses, and garbage sites.
- Rural settings: grain stores, farms, and riverbanks.
- Global presence: established on all continents except Antarctica, thriving in temperate and tropical zones.
Behavioral characteristics
- Omnivorous diet: grains, fruits, insects, carrion, and human waste.
- High reproductive rate: gestation 21–23 days, litters of 6–12 pups, multiple litters per year.
- Social structure: colonies with hierarchical dominance, frequent grooming and scent marking.
- Adaptability: capable of swimming, climbing, and squeezing through openings as small as 1 cm.
Human relevance
- Disease vectors: carriers of leptospirosis, hantavirus, and bacterial pathogens.
- Economic impact: damage to crops, stored food, and infrastructure through gnawing.
- Research subjects: used in laboratory studies on genetics, neurobiology, and toxicology due to physiological similarity to humans.
Notable large specimens recorded in scientific literature include a brown rat captured in New York City measuring 38 cm from nose to tail tip and weighing 820 g. Such individuals illustrate the upper limits of size within the species under conditions of abundant food and limited predation.