A mild winter and poor garbage upkeep throughout the city’s neighborhoods have led to a dramatic increase in Chicago’s brown rat population, according to Chicago ecologists.

Complaints to City Hall have risen drastically, forcing crews to respond more quickly to 311 calls regarding the rat problem. Calls this year have risen from 12,375 in 2011 to 15,895—a 28 percent increase, according to Matt Smith, spokesman for the Department of Streets and Sanitation. The areas most affected include the South Loop, Logan Square and Bucktown.

The department has 15 two-man crews that respond to notifications. Crews have reported using more rat poison than in the past, leading to 18,339 rat kills so far this year, compared to 14,855 documented kills in 2011. The poison is not harmful to humans. Crews are looking to prevent further growth of the brown rat population by placing poison in areas thought to show signs of rodent activity.

According to Smith, the 2nd Ward, which includes the South Loop, has seen the sharpest increase in the rat population, but Alderman Robert Fioretti is taking  the initiative to clean up streets and alleys in the South Loop in an effort to combat the rats. Fioretti and four staff members have been traveling alongside response crews to ensure proper poison distribution throughout the ward.

“If you bait an alley and you don’t bait the alley next to it, then the rodents could travel safely through the alley and keep spreading farther, rendering our plan useless,” Fioretti said.

According to Seth Magle, director of the Urban Wildlife Institute at the Lincoln Park Zoo, the brown rat is largely responsible for the rat population spike because of its ability to effectively locate food and water sources.

Steve Sullivan, head curator of the Peggy Notebaert Nature Museum in Lincoln Park, said the brown rat’s resilience also contributes to the sharp population increase.

“The basics of population increase have to do with food, water, shelter,” Sullivan said. “Food is everywhere.  If you can eat it, a rat can eat it.”

Poison operations have led to an extensive increase in rodent kills, with approximately 1,050 kills in the South Loop so far, said Fioretti. The alderman said he is trying to lead the campaign to reform the response process from one that is reactive to a more proactive approach. He added that other aldermen need to review their current efforts to provide a more comprehensive response plan.

Fioretti believes other wards should be taking notice of his plan, and said residents of surrounding wards are contacting his office looking for solutions to their

rodent problems.

According to Magle, more research on rat populations is needed, rather than simply tracking citywide reports. He said he and his colleagues are developing a program that uses ink-covered tracking plates to trace where the rats go, but the ink often dries up or rubs off before data can be collected, causing scientists to check the

traps more frequently.

Another major concern is that the brown rat is a sign of poor sanitation conditions in Chicago, Sullivan said.

“[The rats] run around and make messes, which can promote a wide range of diseases,” he said. “Since they can reproduce so quickly, they are more problematic than any other urban pest.”

Magle, Sullivan and Fioretti all believe the best way to combat the brown rat population problems is to be proactive and for citizens to take care of waste responsibly.

“The easiest way to make a dent in the population is to make sure your garbage is not accessible to the rats, otherwise your waste will become their food source,” Magle said. “People need to make sure their garbage cans are closed and animal waste is disposed of properly.”