Rattus – Old world rats

Found on every continent except Antarctica, these medium-sized rodents thrive in forests, farms, islands, cities, ships, and sewers alike. What sets Rattus apart from look-alike small mammals is a mix of brains, agility, and social savvy. They’re quick learners with excellent memories, able to map new spaces after a single night’s exploration. Their whiskers act like fingertips, sweeping (“whisking”) to read textures and gaps, while their long, scaly tails help with balance and cooling—handy when dashing along beams or power lines. Unlike many mice, rats carry themselves with a heavier, low-slung confidence, and they tackle bigger jobs: prying open containers, hoarding food, and working together to investigate anything new (and sometimes to avoid it, since many rats are cautious about unfamiliar objects).

Within the genus, two species shape most of our day-to-day encounters—and they’re quite different. The Brown or Norway rat (Rattus norvegicus) is the burrower: stocky, with a tail usually shorter than its body, a strong swimmer, and right at home underground or along waterfronts. It’s the ancestor of lab and pet “fancy” rats, which hints at the species’ remarkable trainability and calm temperament under human care. The Black or Roof rat (Rattus rattus) is the acrobat: slimmer, with a tail often longer than its body, keen on climbing rafters, vines, and trees. Meet a rat in your attic? It’s likely a roof rat. Meet one near a wharf or in a subway? Odds favor the brown rat. Both are omnivores, but roof rats lean toward fruit and seeds when available, while brown rats are bolder scavengers, happily mixing grains, meat scraps, and whatever a city spills.

Rats differ from many other rodents in more than body shape. They’re intensely social, living in flexible groups with pecking orders and cooperative habits. In labs, rats will free a trapped companion and share food with a partner that helped them before—simple, but striking, proof of social memory. They also “laugh”—not a human chuckle, but tiny, high-pitched chirps during play or tickling, a window into their emotional lives. Their teeth never stop growing, so they must gnaw daily, which is why they can worry through wood, plastic, or soft metals if motivated.