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Black Rat

Rodent

Black Rat

The black rat is a slender-bodied rodent with a long tail and large ears. It undergoes a rapid life cycle, with gestation lasting 21–22 days and sexual maturity reached within 12–16 weeks. Adults weigh between 100–300 g and are known for their climbing ability, often inhabiting trees or attic spaces in urban environments. Infestation indicators include sightings, strong urine odours, banana-shaped droppings, visible runways, intermittent smears from oily fur, and gnawing damage.

Facts

  • Name: Black Rat, Rattus rattus
  • Life cycle:  
    Gestation: 21-22 days
    Weaned: 3-4 weeks
    Sexually mature: 12-16 weeks
  • Description:
    Rattus rattus is distinguished by its large ears, slender body, and a tail longer than the combined length of its head and body. Adults typically weigh 100–300 g (average 225 g) and measure 150–220 mm in head and body length. Fur colour ranges from light brown to black, making colour an unreliable identifier. The species exhibits mild neophobia (fear of new objects), though this varies by population and environment.
  • Habitat:

    Adaptable and agile, R. rattus thrives both at ground level and at height. In natural settings, it favours trees, while in urban environments it frequently occupies roof voids and attic spaces. Although capable of ground-level infestation in the absence of predators or competitors, it rarely burrows.

Black rat on the kitchen side

Signs of infestation

  • Sightings: Direct observation remains the most reliable indicator.
  • Smell: A strong, musky urine odour may develop, especially in enclosed or heavily infested areas. Over time, individuals may form urine pillars by repeatedly urinating in the same location.
  • Droppings: Typically 9 mm long, thin, and banana-shaped.
  • Runs: Repeated use of the same pathways can result in visible depressions or cleared vegetation.
  • Smears: Oily fur leaves intermittent smear marks along frequently used routes. These broken smears are characteristic of R. rattus due to its agility.
  • Damage: Continuous gnawing behaviour leads to structural and material damage, often around entry points or food sources.

References
1. BPCA Manual. Chapter 6

Two black rats on a window seal

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