Brown rats: the intelligent threat

The common brown rat (Rattus norvegicus- also referred to as the Norway rat or sewer rat) is a highly destructive mammalian pest found in and around rural and urban settings alike worldwide. Fairly significant in size, weighing approximately 11 ounces and reaching lengths of 13 to 18 inches, including tails that range anywhere from six to eight 1/2 inches, it is often confused with the roof rat. Roof rats, however, are typically smaller and more agile, often nesting in high places such as trees or attics.

Their fur is coarse and mostly brown with scattered black on the upper regions and a yellowish-white to gray underside. Evidence of their presence can be seen by their droppings or signs of fresh gnawing as they need to continuously gnaw in order to keep pace with the rapid growth of their incisors. Burrows and runways are typically visible next to buildings, along fence lines as well as under low vegetation and debris wherever they are present. The have bald ears, small beady eyes and a scaly tail that is shorter than the length of their head and body. 

Brown rat habitat

The brown rats’ ubiquitous presence is legendary. Currently an estimated 150 to 175 million Brown rats live in the United States. They cause millions of dollars in damages to crops and buildings per year. A U.S. government report estimated that each individual rat annually damages $1 to $10 worth of food and other material, and contaminates five to ten times more. They usually eat one third of their weight in one day.

Relying on their ever-growing incisors and powerful jaws, they wreck havoc by burrowing underneath walkways and buildings and gnawing through walls, pipes and electrical wires, often unwittingly causing fires. Additionally they have started floods by tunneling through dams. They contaminate crops and food while also restricting plant growth by consuming large amounts of seeds. The brown rat is quite the formidable pest.

Are brown rats dangerous?

The brown rat transmits diseases directly by biting people and contaminating food, and indirectly by carrying lice and fleas. Historically they have been vectors for bubonic plague, leptospirosis, tularemia, spotted fever, Hanta virus, typhus, salmonella food poisoning, infectious jaundice as well as a whole slew of other diseases.

Due to their preferable close proximity to humans, who unwittingly provide food and shelter for them, the threats of disease are particularly worrisome. Their rates of reproduction are equally disturbing. They have been known to bite babies in their cribs as the smell of milk attracts them.

What do brown rats eat?

They will eat almost anything, but prefer meats and fresh grains. They require a half an ounce to one ounce of water, daily, while feeding on dry food. Rats have a keen sense of taste, smell and hearing and will access any structure as long as the opening is at least one half of an inch across. Brown rats are prolific breeders who will reproduce all year long, only limited by the availability of food.

When do brown rats breed?

Females typically have about seven young per litter and six to eight litters per year. They also experience a postpartum estrus and are able to mate a mere 18 hours after giving birth. Their young are completely independent after approximately four weeks and they reach sexual maturity at three months. Males tend to reproduce later when they are larger and can challenge dominant males. Brown rats will reproduce until they are one and a half to two years of age, where the lifespan is three years old.

Let Ehrlich help!

Because brown rats can cause such a mess, it is important to take care of any potential problems right away. Sanitation is paramount. Seal any openings greater than one half inch across and contact Ehrlich for the much needed additional assistance with rat control.