The Perfect Storm for Resilient Rats

Britain is enduring the wettest winter for 130 years, with experts from the National Infrastructure Commission warning that intense rainfall leading to extreme weather events such as flooding, are increasingly more likely as a knock-on effect of climate change.

Amid the turmoil of dealing with the destruction and flooding of homes and businesses, is the need for awareness that climate change is providing the perfect storm for increased problems from rats. Our National Account and Technical Manager UK & Ireland, Richard Faulkner explains: 

“Winters are very mild now, so we don’t get the consistent weeks of frost and very cold weather that naturally knock down rodent populations. With the number of storms and increased rainfall, we’re seeing more rats, as they’re driven out of sewer and drainage systems and their natural burrow sites due to flooding and the rise in levels of ground water.”

In colder months rats are already on the lookout for warmer places to live which makes poorly maintained and flood-damaged buildings prime targets for infestations. Add to this the destruction and debris caused by storms and flooding, and rats will be forced upwards from sewers and burrows to seek new places to live where there is suitable cover and a good source of food. 

Rats Resilient to Flooding

“Our common rats are subterranean, and sewers make a perfect habitat,” says Richard. “The mix of storm and foul water in sewer systems provides rats with all they need, which is food, water, and harbourage. They will find food in foul water systems, and they need 60mm of drinking water a day to survive. Also, with no predators in sewers, rats aren’t at danger from birds of prey, as they would be above ground. Sewers are also warmed from foul water, so make attractive homes for rats, especially in the winter months.

“Rats are very well adapted to water. They can tread water for up to 3 days and can swim for a distance of up to half a mile. I’ve seen them propel themselves in water very efficiently, using their tails like rudders! Rats are tenacious creatures, so in floods they will simply swim to safety and find a new home in a suitable area with food, water, and harbourage.” 

Preventing Rats after Storms and Flooding

Even after flood damage our houses still make perfect homes for rats. Relocation is aided by their nocturnal habit and the ability to stealthily hide and move under the cover of the debris and rubbish that accumulates in excess after storms. “In properties that have been extended or renovated, they will often travel in old drains that are no longer used and haven’t been capped off. These create perfect rat runways, that can give rats easy access into buildings,” Richard adds. “Cavity walls and timber frames, attics and even under-floor heating all provide cavities that make attractive habitats.”

Preventing rats from moving in after flooding relies on basic preventative actions. “Look for points of entry into buildings and address these,” Richard advises. “Clear debris, cut back vegetation and get rubbish away as soon as possible, to make sure there are no easy places for relocating rats to hide. Basically, the outside environment near buildings needs to be as uninviting to rodents as possible.

“Don’t forget that rats and mice can fit through tiny gaps, so where pipes or wires run into a building or where there are vents, extra vigilance is needed,” says Richard. “Mice can fit through any gap larger than 5mm in circumference, and rats can enter buildings through holes the size of a 10p piece. As a rule of thumb, if you can get a pen into a gap, you need to block it.”

Understanding Rat Behaviour Essential for Prevention and Control

An understanding of rats’ habits and behaviours is a vital tool when controlling infestations, explains Richard. “Rats are creatures of habit and like to use the same routes; ideally close to walls, using special guard hairs on their coats to help guide them in the dark. They also benefit from kinethesis (a type of muscle memory). This means they learn their preferred routes and are able to find them again and again. Even when startled, muscle memory will kick in to help a rat find its regular tried and tested exit point.” 

Richard explains: “This is a really important tool for pest control officers (PCOs), as we know rats will use the same route repeatedly. Grease on a rat’s coat will also leave tell-tale smear marks on walls, pipes or other surfaces they regularly rub against. This helps pest controllers enormously, in finding the best locations for bait and traps.”
A clear understanding of the social behaviour of rats and mice will also help when planning monitoring and control strategies, especially in situations like storms and flooding that force the rodents to move.

“Rats (and house mice) live in established family groups, with a distinct hierarchy,” Richard explains. “Dominant males are usually the first to succumb to baiting because they have first rights to food, but then the subordinate family members will move in to replace them. This is a vital thing that people don’t often understand about pest control. 

“While nature dictates that dominant rats will be extinguished first; remember, the rats wouldn’t be there at all unless the habitat was right for them. They’re living where they’ve got the right food, water, and safe harbourage. So, all that happens when a quick fix baiting approach is used, is that prime real estate is freed up for new infestations from subordinate rodents in the surrounding peripheral areas. Also, if the essential housekeeping is not done to prevent infestations - like removing vegetation, rubbish and proofing buildings - then inaction is just clearing the way for the next tier in the hierarchy to move in. This is why monitoring as part of an Integrated Pest Management strategy is always so essential.”  

Safety of Pest Control Officers Vital After Flooding

Whatever the weather, safety and protection of the environment is essential when treating infestations. “When tackling rat problems after flooded conditions and stormy weather, it’s vital not to bait where any chemical could be washed away. Protection of the environment is key,” reminds Richard.

“For PCOs, there’s also an increased personal risk when tackling infestations after flooding. Our common rats carry Weil’s disease, a form of Leptospirosis. The spirochete bacteria that cause Weil’s disease are brilliant at surviving in wet conditions, so PPE is very important for pest controllers working in previously flooded areas that are still damp. If you have had flood damage, it’s also imperative that everything is washed down and then treated with a bacterial biocide to prevent infection from spirochete bacteria.”


At Envu we provide the products and advice needed to control rat infestations all year round, whatever the weather. For further information click through to our rodent products and information pages and read more about following an Integrated Pest Management approach too.