As Northern Ireland emerges from its sub-zero temperatures, two populations appear not to have fared so well in the big freeze.
An apparent absence of house mice and rats has had a knock-on effect at Belfast City Council.
The council's pest control department has said there has been a decrease in calls over mice and rat problems during December.
The council says calls over rat problems were down in December
The Council's Pest Control Manager, Earl d'Hulst, said both populations may have been hit by a combination of the severe cold and lack of food in some of their habitats including sheds and garages.
The council provides a pest control service to both domestic and commercial rate payers. The council area takes in about 160,000 domestic properties.
Mr d'Hulst said, although December was generally a slower month, calls for help over mice and rat problems were down compared to September.
"We received 267 calls from the public in December compared to over 500 in September," he said.
He said: "At the beginning of December, anyone requesting an appointment would have been seen by a pest control officer within five to seven days.
"Due to the decrease in calls, it is possible for anyone with a pest problem to be seen much sooner," he said.
Professor Ian Montgomery, from the Animal Ecology Department at Queen's University, said the populations would be vulnerable in cold temperatures, particularly temperatures under -5C.
Professor Montgomery said: "The cold, combined with a decrease in breeding during winter months, would led to lower numbers.
"In order to survive the sub-zero temperatures, rats would go below ground into sewers and drains to survive," he said.
Mr d'Hulst said he believed any thaw would led to the resilient rodents reappearing.
The National Rodent Survey of 2008 conducted by the National Pest Technicians Association indicated a marked increase of both rat and mouse problems across the UK.
So, as the mercury begins to move up the thermometer, Mr d'Hulst is predicting business could be back to normal levels in the coming months.