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Brown Rat

Rodent

Brown Rat

Brown rats typically have plain brown fur and live communally in burrows with multiple entry points, often situated around buildings. Signs of infestation include sightings, distinctive urine odours, spindle-shaped droppings, visible runways, footprints with tail swipes, and gnawing damage characterised by grooves approximately 3 mm apart.

Facts

  • Name: Brown Rat, Rattus norvegicus
  • Life cycle:  
    Gestation: 21-24 days
    Weaned: 3-4 weeks
    Sexually mature: 12-16 weeks
  • Description:
    Brown rats have a short muzzle and a heavy-set body, with a tail shorter than the combined length of the head and body. Adults weigh between 250–500 g and typically measure 200–270 mm in head and body length. While most R. norvegicus have plain brown fur, colour alone is not a reliable identifier. The species exhibits a pronounced neophobic response (fear of new objects), which can affect baiting and control strategies.
  • Habitat:

    R. norvegicus lives communally in burrows, which often feature multiple entry and exit points. These burrows are commonly found in earth banks around buildings and, on occasion, beneath structures.

Brown rat sitting on bin bags

Signs of infestation

  • Sightings: Direct observation remains the most reliable indicator of infestation
  • Smell: A strong, musky urine odour may develop, especially in enclosed or heavily infested areas
  • Droppings: Typically 12 mm long and spindle-shaped
  • Runs: Repeated use of the same pathways can result in visible depressions or cleared vegetation leading from burrows
  • Footprints and Tail Swipes: Rats drag their tails as they move, leaving distinctive marks that help differentiate their tracks from those of mice
  • Damage: Continuous gnawing behaviour leads to structural damage; R. norvegicus can be identified by gnaw marks with grooves approximately 3 mm apart

References

  1. BPCA Manual. Chapter 6
Brown rat in a house

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