Roof Rats

March 2024 Edition by Brian Beidle, BCE

Dealing with structural rodents can certainly be a challenge, particularly after they’ve become established. As warmer temperatures push their way to the north, the threat of acquiring roof rats at your facility will increase.

Many of us deal with house mice all the time at seed and grain facilities, as well as potentially at bakeries and flour mills. Rats, however, are less seldom encountered, and when they are, Norway rats may enter an exterior station eat a large amount of bait, and then are killed.  Not so much with the roof rat.

The roof rat is a climber as per name would suggest. What’s worse, it is afraid to come to ground level to get what it needs, and even so when at ground level is often extremely nimble and very skittish.

To be afraid or cautious of new things is called neophobia and is a behavior in rats and mice. The rat can be one of the more neophobic creatures.  What’s more, it’s typically more at home in higher levels, including ceiling voids, ceiling level beams or utilities, rooftops, and exterior overhead utility lines of every kind.

Knowing a roof rat from a Norway rat takes a bit of skill and some hands-on technique. The basic identification process is to take a dead rat that’s in good condition while wearing gloves and pull its tail over its back like a scorpion.  A Norway rat with an intact tail will not pass the ears on the head of the rat, whereas a roof rat’s tail will easily make it to the nose and often past the nose. The color of the rat is a very poor indicator despite the name brown and black rat.

Norway rats and roof rats can have the exact same color fur so don’t use that for identification purposes.

Lastly, consider juvenile rats versus adult mice.

Sometimes very young rats can be confused with house mice.  If they are caught in a snap trap, or even less common inside of a repeater, do look for certain features. Young rats have a very large head in proportion to their body and their back foot is extremely large in proportion to their body. You may notice that the hind feet look more like a frog or a toad foot as opposed to a rodent. This will be a dead giveaway when you’re looking at a rat and not a mouse.

Just like the house mouse, both the Norway rat and the roof rat have a scaly tail with hair, but not furry like you would find with a deer mouse.

Please make use of technical resources when you’re unsure and take very good photographs of rats when killed to ensure you’re not looking in the wrong places and that you’re trapping, poisoning, and fumigation efforts will be successful.  Should an account be verified to have roof rats inside and they are established, know it can take a very large amount of time to gain control with traditional IPM methods.  A fumigation should be tabled for discussion if at all possible, for a quicker knockdown and control