Rats

Rats are medium-sized rodents of the genus Rattus, with two species accounting for most human encounters: the brown rat (Rattus norvegicus) and the black rat (Rattus rattus). They are native to Asia but have been introduced worldwide and are highly adaptable to varied environments, especially urban settings where food waste provides abundant calories. Rats are omnivorous and opportunistic feeders; their diets include grains, seeds, fruits, garbage, and small animals.

Adult brown rats measure about 20–25 cm in body length, with a tail of a similar length; they can weigh 350–500 g. Black rats are smaller (about 12–18 cm) with relatively longer tails. Both have sharp incisor teeth that continually grow and require gnawing. They are primarily nocturnal, good climbers (more so for black rats) and capable swimmers. Lifespan in the wild is typically 1–2 years.

Rats breed year-round in human-sized environments. Gestation 21–23 days; litter sizes 6–12; several litters per year. They form social groups with hierarchical structures and produce nest materials in walls, sewers, or burrows. They are highly adaptable in navigation, can learn mazes, and communicate by vocalizations and pheromones.

Rats can carry and spread pathogens including Leptospira (leptospirosis), Salmonella, and others; fleas on rats were vectors for plague in the past. In urban areas, contamination of food and water is a concern.

Control relies on sanitation, exclusion, and population reduction using traps and, when necessary, rodenticides in tamper-resistant stations, integrated pest management. Long-term strategies emphasize removing food sources and entry points to reduce reliance on chemicals.