How to Identify Commensal Rodents with Globe and Bell Labs

How to Identify Commensal Rodents with Globe and Bell Labs: Rodent Management 101


In Australia we have more than 60 native rodent species! These rodents play an important role in a healthy ecosystem, contributing to soil turnover and dispersing seeds and fungi, as well as being a vital link in the food chain. However, it is the three introduced pest species: the Norway rat, the roof rat and the house mouse, that professional pest technicians deal with day-to-day.

These three introduced species are also known as commensal rodents, meaning to ‘share one’s table’, are gnawing and nibbling mammals, living at humans’ expense without contributing anything valuable to the relationship.

At Globe Pest Solutions, we've partnered with Bell Labs to help Australian pest technicians make heads or tails of commensal rodent control.

The Norway Rat / Brown Rat

How to identify a Norway rat

The Norway rat (Rattus norvegicus), also commonly referred to as the brown rat, common rat, sewer rat and water rat is the larger of the two pest rats. Norway rats can be twice the size of the roof rat, characterised by reddish-brown fur, small eyes and ears and a thick body.

If you were to hear the term ‘rat the size of a cat’, it is likely to be a sighting of a mature Norway rat, with their size varying from 280g-480g, the head and body being 20-30cm long, extending as long as 30-45cm long including the tail.

Norway rat identification and characteristics

Where are Norway rats usually found?

The Norway rat is an excellent swimmer, digger and climber, and would generally prefer to be nested in burrows, basements and lower portions of the buildings. They can have extensive burrows in soil around properties. Entering properties on the ground level through drains, pipes and exposed entry points. If you ever encounter the ‘rat up the toilet’, its likely to be a Norway. 

The Roof Rat / Black Rat

How to identify a Roof rat

The Roof rat (Rattus rattus), also commonly referred to as the black rat, or ship rat, is most easily distinguished by the length of its tail, being longer than the head and body combined. Focus on the tail when trying to distinguish between juvenile roof rats and mice. The roof rat is noticeably more slender than a Norway rat, with a weight between 140 to 250g, usually with grey, black or brown fur, a pointy nose and large eyes and ears. Lengthwise, they will still be from 30-45cm, however, due to this long tail, the head and body might only be 18-25cm.

Roof rat identification and characteristics

Where are roof rats usually found?

The Roof rat is an exceptional climber and jumper, entering and nesting in upper portions of buildings or structures. Roof voids or rafters are a very common spot, and they can even swing from overhanging tree branches or vegetation into properties. Its also very common for rodents to nest in these trees, palms in particular.

If a consistent food source and sufficient harbourage is available at height, a roof rat may live its entire life without coming into contact with the ground.  This can make it difficult to eradicate, especially if all control tools are located at ground level.

Keep in mind that both Norway rat and Roof rat species are very adaptable however and will change habits to adapt to continue to enter properties undetected. Rats are more prevalent in built-up city and coastal areas, however once again, have adapted to all environments humans inhabit.

The House Mouse

How to identify a house mouse

The House mouse (Mus musculus), is the smallest of the commensal rodents, with brown or grey fur, a small slender build, pointy nose, with large eyes and ears. The house mouse weighs up to 20g, with a head and body at 8-10cm, and up to 20cm long including the tail.

House Mouse Identification and Characteristsics

Where are house mice usually found?

The House mouse, as per its name is usually found in and around houses, at ground level as well as up in roof voids and attics. Interestingly it is also the house mouse that can be found in grain crops, and when conditions are favourable, in plague proportions like in Western NSW throughout 2021. Uniquely, Australia and a province in China are the only two places on the planet that experience mouse plagues like this, and with a change in farming practices, it is a once every 5-to-10-year phenomenon. 

Why are commensal rodents considered pests?

Commensal rodents cause devastating damage in a wide range of settings, it is estimated they consume, damage or contaminate about 20% of the world’s food supply, before it gets to the table. They also gnaw, imperative to work down their incisor teeth, causing extensive structural damage, causing fires gnawing electrical wires, and water damage or flooding if through water pipes.

Rodents also carry and spread serious diseases, such as foodborne illnesses, Typhus, Leptospirosis, Asthma, Hantavirus, LCM and Lyme disease, as well as being the host for the bubonic plague, one of the deadliest diseases that humanity has ever faced.

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