Rats are a diverse group of rodents found across the globe, inhabiting nearly every continent. While often perceived as a single entity, the term “rat” encompasses a surprising array of species, each uniquely adapted to its environment. These creatures have successfully coexisted with humans for centuries, demonstrating remarkable adaptability to various landscapes, from dense forests to bustling urban centers.
The Vast World of Rats: Understanding the Numbers
The common name “rat” is applied to many different rodent species, leading to a broader perception than scientific classification suggests. Within the order Rodentia, the term typically refers to medium-sized, long-tailed rodents. While a smaller muroid rodent is generally called a “mouse,” this distinction is not taxonomically precise.
“True rats” belong specifically to the genus Rattus, which originated in Asia. This genus alone includes approximately 56 to 68 known species, depending on the classification system followed. Beyond the Rattus genus, numerous other rodent genera and families also contain species commonly referred to as rats due to their similar appearance and characteristics. These include diverse groups like the North American pack rats (Neotoma), bandicoot rats (Bandicota), and kangaroo rats (Dipodomys).
The Most Widespread Rat Species
Among the Rattus genus, three species are globally widespread and commonly associated with human habitats. The Norway rat (Rattus norvegicus), also known as the brown rat, is a stocky rodent typically measuring 16 inches long, including its tail. Its fur is coarse and usually grayish-brown, with a lighter underside, and its tail is shorter than its head and body combined. Norway rats are primarily ground-dwelling burrowers, constructing tunnel systems along property lines, under concrete slabs, and in basements or sewers. They are omnivorous, consuming nearly any food, though they show a preference for cereal grains, meats, and fish.
The roof rat (Rattus rattus), also called the black rat or ship rat, is more slender than the Norway rat, typically 13 to 15 inches long, including its tail. Its fur can range from grayish to dark gray or black, with a lighter underside, and its tail is longer than its head and body combined. As their name suggests, roof rats are adept climbers, preferring elevated habitats like trees, attics, and rooflines, using their nimble feet and tail for balance. They are omnivores, with a particular fondness for fruits, nuts, and seeds.
The Polynesian rat (Rattus exulans), sometimes called the Pacific rat, is the third most widespread “true rat” species. It is smaller than both the Norway and roof rats, with a slender body typically 4.5 to 6 inches long and a tail of similar length. Its fur is ruddy-brown on the back with a whitish belly, and it has large ears and a pointed snout. Originating in Southeast Asia, Polynesian rats have spread across thousands of Pacific islands, often carried by human voyagers. These rats inhabit diverse environments, including grasslands, forests, and cultivated lands, and are skilled climbers, sometimes nesting in trees.
Beyond the Familiar: Other Diverse Rat Groups
Beyond the globally recognized species, the world of “rats” includes many rodents with unique adaptations. Kangaroo rats (Dipodomys genus), native to the deserts of the Southwestern U.S., are not true rats but are named for their powerful hind legs allowing them to leap up to nine feet to escape predators. These desert dwellers possess water conservation abilities, often surviving without drinking any water by metabolizing moisture from their seed diet. They also have external, fur-lined cheek pouches used for carrying seeds back to their burrows.
African pouched rats (Cricetomys genus) are another distinct group, known for their large size, with some species reaching up to three feet in length, including their tail. These nocturnal rodents are characterized by prominent cheek pouches, similar to hamsters, which they use to gather and transport significant amounts of food back to their underground burrows. Their sense of smell, particularly their large olfactory bulbs, allows them to detect faint scents, leading to their training for specialized tasks like landmine detection.
Cloud rats, such as the Northern Luzon giant cloud rat (Crateromys schadenbergi) from the Philippines, are arboreal rodents. These forest-dwelling animals have thick, soft fur, which provides insulation in their cool, mountainous habitats. They are excellent climbers, with large hind feet and strong claws, spending most of their lives high in the tree canopy. Their auditory abilities also help them detect high-frequency sounds, aiding in predator avoidance and foraging in their low-light environments.