### Identification The Brown Rat is a robust, heavy-set rodent, typically measuring 20–28 cm with a thick, scaly tail slightly shorter than its body. Its fur is coarse and "agouti"—a grizzled mix of brown and grey with a paler underside. To distinguish it from the similar Black Rat (*Rattus rattus*), look at the head: the Brown Rat has a blunt muzzle and notably small, furred ears that do not reach the eyes when pulled forward. Its eyes are small and bead-like, suited for a life in the shadows.
### Habitat & Range Originally native to temperate Asia, this ultimate opportunist has followed human trade routes to every continent except Antarctica. It is a "commensal" species, thriving wherever humans dwell. You’ll find them in urban sewers, damp basements, and subway tunnels, but also in rural hedgerows, riverbanks, and salt marshes. They are exceptional burrowers, preferring to stay at low elevations near a reliable water source.
### Behaviour Primarily nocturnal and crepuscular, the Brown Rat is a social engineer. They live in complex hierarchical colonies, often excavating intricate burrow systems with "bolt holes" for emergency exits. In the field, look for "runways"—greasy, well-worn paths along walls or through vegetation caused by the oils in their fur. They are famously "neophobic," meaning they are deeply suspicious of new objects in their environment, a trait that makes them remarkably resilient.
### Diet As true generalists, they forage for almost anything. While they prefer grains and seeds, they are also skilled predators, known to hunt small birds, fish, and amphibians. Their powerful incisors can exert a pressure of 7,000 psi, allowing them to gnaw through lead pipes and cinder blocks to reach a food source.
### Fascinating Fact Brown Rats are surprisingly "cheerful" socialites! Research has shown that when they play or are tickled by researchers, they emit ultrasonic chirps (around 50 kHz) that are functionally equivalent to human laughter. This "giggling" helps them bond and reinforces social ties within the colony.