Calls have been pouring into our Sacramento pest control office, with homeowners and business owners reporting that, suddenly, rats have moved into their attics and garages.

Now rat problems always grow worse during our chilly, rainy Sacramento winters, because, like us, the rats are looking for a cozy, dry place indoors where they can build nests and have babies... lots and lots of babies—three to five litters per year, and as many as eight rat pups per litter!

But this year we’re seeing something a little different: The rats our expert pest control technicians are pulling out of the traps they place are huge... some of them nearly a foot-and-a-half long, measuring both body and tail.

What could be creating this bumper crop of plus-size rats? People pouring multi-vitamins down the kitchen sink? Radiation from so many people constantly using their cell phones?

No, far from being a plot line from an upcoming sci-fi movie, the fat and happy rats we’re seeing are simply the products of a series of fairly mild winters in the Sacramento region. Whereas in a normal winter, a large proportion of rats naturally succumb to cold, exposure and scarcity of food, in a mild winter, more rats live to see the spring. A rat whose normal life span might be two years may live to be three, growing correspondingly larger with age. Foods that rats like, such as seeds and grains, are more abundant during mild years, so the surviving rats get plenty to eat.

There are numerous examples of mild winters leading to a boom in rat populations. In 2002, the city of Boston was overrun with rats; thanks to a series of mild New England winters, instead of some 30 percent of rats dying off in frigid cold, only about 5 percent succumbed, according to the Boston Phoenix newspaper (http://www.bostonphoenix.com/boston/news_features/top/features/documents/02194425.htm).

A 2009 article in the UK Guardian newspaper reports the worst rat infestation in 30 years, due to a run of mild winters, and warns consumers that the overpopulation of rats, combined with a bumper wheat crop could increase the danger of rodent droppings in whole-grain breads. Foods made with whole grain flour were more susceptible to rat droppings, the article stated, because they are less processed than goods made with white flour.

Perhaps the most amusing—if alarming—example of rats gone wild was the 2002 Los Angeles Times article reporting that rats seemed drawn to the lifestyles of the rich and famous. One well-to-do Beverly Hills doctor and his party guests were horrified to discover three rats helping themselves to his outdoor buffet. Just a few days later, on a warm Saturday afternoon, the physician found five rats swimming in his marble pool. The culprit: several mild Southern California winters in a row, coupled with near-drought conditions (similar to recent climate conditions in our Sacramento region) that drove the rats from fields and vacant lots into the lush, well-watered gardens and patios of upscale L.A. (http://www.nytimes.com/2002/09/17/us/up-down-in-and-out-in-beverly-hills-rats.html?pagewanted=1)

While such tales may make us laugh, the fact is that rats pose a danger to our homes, families and businesses and to the public health. In addition to carrying diseases and contaminating foodstuffs, rats pose a fire hazard due to their constant gnawing.

Because their four long incisor teeth grow very rapidly and continually throughout the rats’ lifespan, they must constantly gnaw to keep the teeth worn down (http://www.ratbehavior.org/Teeth.htm). If they were to stop, their long, sharp front teeth would grow in spirals and impale them. Among rats’ favorite teething toys appear to be electrical wires, telephone wires, satellite and cable TV wiring and alarm-system wires—at best a nuisance or a repair bill, at worst a fire that destroys a home or place of business.

Rat infestations are a stubborn pest control problem best left to licensed and trained pest control professionals. To learn more about rats and other rodents and how to prevent infestations, read our earlier blog post at http://earthguardpest.com/blog/?p=21 or visit www.earthguardpest.com.