As of Thursday afternoon, a total of 77 Norway rats had been found and killed in the Medicine Hat area, and officials acknowledge there's the potential hundreds more are prowling in different spots.
Ed Jollymore, the city's solid waste utility manager, said they found 53 rodents in the landfill, 19 within its vicinity and five others at isolated spots as of Thursday afternoon.
The colony of rats, initially discovered in the area last week, could number in the hundreds, but there's no way to determine an exact count, said Jollymore.
"To say that there's 100, 200 or more is really speculative," he said. "Last (week) when we started we knew there were four and to say that there were 53 would have been purely speculative."
Brandy Calvert, a spokeswoman for the city about 300 km southeast of Calgary, said a 5-km perimeter around the landfill has been baited with poison to coax other vermin that may still be hiding.
"We're not going to be the ones that brings down the province's standing as rat-free," said Calvert. "We are determined and the province is determined that this will be taken care of."
Jollymore said they have deployed three different kinds of traps and digital cameras to monitor the movement of rodents that may still be prowling in the area.
Risk spots, such as pumping stations within the city limits, have also been treated with baited traps to make sure no vermin escapes the hunt.
Jollymore said it's likely rat monitoring in the area will continue for several months to be sure they get rid off all the pests.
John Patton, president of the Pest Management Association of Alberta, said all the rats found in the Medicine Hat area likely belong to just one colony.
"It's just the behaviour of the Norway rats, they would tend to colonize together that's what they do," he said.
Norway rats are "extremely intelligent" animals that can adapt in land or water, which is why exterminators have to deal with them, said Patton.
"They're killed with extreme prejudice," he said. "You pretty well have to pull all the tricks out of the arsenal."
Patton said the only drawback is that most of the exterminators trained in the province have never actually dealt with rats, which is part of the reason the Alberta Agriculture is involved in helping eradicate the pest.