A wave of development has brought thousands of new residents and nightlife patrons downtown, and they’re often surprised to find themselves in close encounters of the rodent kind.

Whether in Pershing Square, the basements of rehabbed historic core buildings or on the sidewalks of Bunker Hill, rats can be seen scurrying all over downtown, especially at night.

“You see them everywhere and they’re not cute little mice,” said Ginny-Marie Case, a three-year resident of downtown Los Angeles and a member of downtown’s neighborhood council. “Some of them are bigger than the little puppies people walk around with.”

Increased rat sightings are certainly a result of the unprecedented construction boom in downtown, where many of the area’s abandoned office and warehouse buildings have been converted into lofts, depriving rats of hideaways and adding thousands of residents.

Sightings have become the talk of coffee shop conversations and rooftop parties all over downtown, with many residents boasting of the run-ins as a badge of honor in urban pioneering.

“They’re a common sighting when walking around at night,” said Janene Zakrajsek, a downtown resident who recently opened a pet supply store a few minutes’ walk from her loft. “It’s kind of creepy but cool. I get more creeped out by roaches. The rats are just a part of urban living.”

Russell Brown, president of the Downtown Neighborhood Council, agreed. “I will see them occasionally when I am walking around but I don’t feel any degree of discomfort,” he said. “I think they are more scared of us than we are scared of them.”

As opposed to suburban locations where tree-climbing roof rats abound, in downtown Los Angeles the bigger Norway rat is dominant, according to Gail VanGordon, acting chief of Los Angeles County’s vector management program.

“The conditions in downtown Los Angeles are very favorable to the biology and behavior of Norway rats,” VanGordon said. “They prefer sewers, alleys and abandoned buildings, all of which are prevalent in downtown Los Angeles.”

The Norway rat, which is also referred to as the brown rat and sewer rat, is also present in other urban areas such as San Francisco. VanGordon said Norway rats have probably been in downtown Los Angeles for over 100 years.

The county has monitored and deployed abatement measures in downtown and deployed rodent abatement measures. The Norway rats in downtown are the only rodent populations in the county that are actively monitored, although precise numbers aren’t available.

The county has three inspectors devoted exclusively to downtown and conducts a twice-monthly night baiting program targeting rats.

The human population in the city center has increased by 20 percent from 2005 to 2007, reaching over 28,000. The population is predicted to surpass 40,000 by the end of this year. More residents produce more trash, and trash is a lure for rats.

Many building managers and business owners, especially those in the food preparation industry, were reluctant to talk about their efforts at rodent abatement. But traps deployed by rodent abatement companies are present outside many buildings, clear evidence of rat issues.

Even so, some downtown business owners said they’ve never seen a rat in the area.

“I have been here seven years I have never seen any rats,” said Aaron Morquecho, the owner of Angelic Flora Studios. “Even when I am walking to my car.”

Gary Warfel, president of the Titan Organization, a downtown real estate development company, is among those who do not see downtown’s rodent population as a problem.

“I relocated here about 18 months ago and I have never seen a rat in downtown Los Angeles,” Warfel said. “Before coming here, I lived in New York for 20 years. I have seen some rats there.”

Rodent abatement and extermination companies have seen an increase in their business as more buildings have been rehabbed and as more people have moved into downtown.

Anaheim-based Western Extermination Co., which provides services to a number of buildings and companies in downtown Los Angeles, has seen a spike in business in that area in recent years.

The company’s extermination and abatement services include addressing how the rodents are gaining access to a building and placing traps.

Michael Lawton, vice president for commercial services at Western, estimated that the company’s downtown business has increased about 10 percent each year for the past five years.

“Rodent control in downtown Los Angeles is an incredible market for us,” he said. “It goes up every year.”