Roof Rat Populations on the Rise: What to Know

The year 2020 brought us many surprises, including an influx of rodent headlines. Throughout the year, rodents made an appearance across the U.S. in alarming ways, demonstrating aggressive behavior due to a lack of food sources during the coronavirus pandemic and transmitting rat Hepatitis E to humans. Even the CDC issued “Rodent Control" guidance.

Among these infamous rodents are roof rats, scientifically known as Rattus rattus. More slender and agile than the common Norway rat, roof rats present a unique set of challenges. As their name suggests, roof rats prefer higher elevations, so they climb on power lines or tree branches to get on the roof of a building. One there, they can remain undetected, hiding in attics and above eye level. And, their presence has notably risen and expanded throughout the U.S. over the last 15 years.

Dissecting the Data

Historically, roof rats, also referred to as “ship rats,” typically inhabited ports and industrial areas. This meant that U.S. coasts were hot spots for these rodents. However, new data suggests that roof rat populations have spread exponentially between 2005 and 2020.

Roof Rats in the U.S.

In 2005, the National Pest Management Association (NPMA) released a map reflecting roof rat populations across the U.S. The most impacted regions were coastal areas, including the West Coast, East Coast and Southeast. In 2020, Orkin developed a similar map (based on the company’s service data) to document current roof rat populations across the nation. Side-by-side, the maps illustrate the tremendous increase in roof rat populations not only across the West and East Coasts, but also well into the middle of the country.

It’s no coincidence that roof rat populations have increased along major interstates. The spread of roof rats can be attributed to the growth of U.S. infrastructure and distribution centers, as well as the increase in transportation via railways and semi-tractor-trailer trucks into new hubs. Increased U.S. dependence on the transport of goods and materials meant increased shipping rates. As goods left the ports to make their way into the central U.S., so did the roof rats.

Understanding the Effects

The data shows that roof rats are initially spreading to new industrial areas and affecting commercial properties—most notably impacting food processing, logistics and foodservice facilities. However, nothing inhibits roof rats from spreading to residential environments. An increased presence of these rodents anywhere can introduce new health and safety risks.

The most notable risk, especially in the wake of the pandemic, is their ability to spread diseases. Roof rats can contaminate items with their droppings and saliva, spreading salmonellosis and transmitting foodborne illnesses. For facilities handling meat, these rodents are especially troublesome, as trichinosis may be contracted through eating undercooked meat of animals that have fed on rats.

Armed with powerful teeth, roof rats can also cause structural damage and make their way inside just about any structure. From chewing on electrical wires, damaging food product and packaging, and ripping up insulation, these small pests can have a mighty impact. And since roof rats can fit through holes as small as one-half inch in diameter, they are quick to detect entry points, squeezing through damaged vent covers and gaps in fascia and cracks. Roof rats have no problem reaching almost any area of a facility, making them difficult to keep out. Couple that with their ability to breed year-round, and the presence of a few can quickly multiply.

Because they are difficult to control and cannot be treated the same way as common Norway rats, roof rats require working with a pest management professional who recognizes the difference. Orkin Pros undergo extensive training to help manage roof rats for this very reason. And since every building is different, we will design a unique program for your situation utilizing our expert knowledge and experience.

Rodent activity, of course, isn’t limited to roof rats. That’s why our experts put together a free rodent ebook highlighting the different types of rodents and risks they bring. Be sure to arm your facility against these pests so they don’t gnaw into your bottom line. For more information on how to help prevent rodents in your facility schedule a free inspection with an Orkin Pro™.