Gestation: 21-24 days
Weaned: 3-4 weeks
Sexually Mature: 12-16 weeks
A short muzzle and a heavy body, with a tail shorter than the combined length of the body and head. An adult will weight, 250-500g and will have a combined head and body length of roughly 200-270mm when adult. Most R.norvergicus will have plain brown fur, but this is no guarantee of species.
Show a clear Neophobic (fear of new objects) response.
R.norvergicus live communally in burrows, a typical burrow may have multiples entry and exit points. Burrows are usually found in earth banks around buildings and occasionally underneath them.
• Sightings – The surest sign of any infestation.
• Smell – Rodents produce a distinctive odour in their urine. This can be particularly pronounced if the population is confined to an enclosed space or is very large.
• Droppings – Are on average 12mm long and described as being spindle shaped.
• Runs – Rodents reuse the same runs to such an extent that depressions in the earth and paths cleared of vegetation can be clearly seen leading away from burrows.
• Footprints and tail swipes – Rats move with their tails dragging on the floor, this distinguishes their tracks from those of the house mouse.
• Damage – Perhaps one of the clearest signs of rodents is the damage they cause by their perpetual need to gnaw. R.norvegicus can be distinguished by the grooves caused by the incisors being roughly 3mm apart.
BPCA Manual, Chapter 6.