Wednesday, Feb. 25, 2004 | 11:19 a.m.
If you think you have roof rats, call the Clark County Health District's Environmental Health Division at 383-1261.
Since 1991, as 800,000 new residents have made the Las Vegas Valley their home, the area has drawn another group to its burgeoning neighborhoods.
In recent years, roof rats were brought into Southern Nevada, usually in shipments of palm and fruit trees.
Now Clark County health officials, as well as state agriculture leaders and local exterminators, are monitoring the pests and trying to educate the public to keep the vermin from creating an infestation as bad as one that has overrun Phoenix and some of its suburbs.
February and March are peak breeding months for the roof rat, a black rat that likes to move into attics of homes and has a tendency to gnaw through wires.
Late last year roof rats established a colony in Mayor Oscar Goodman's neighborhood, the posh Scotch 80s in central Las Vegas.
Vivek Raman, a health district environmental health specialist who conducted the county operation to trap and test rats in Scotch 80s and the McNeil Tract, said the rodents were crafty foes.
"People don't give these rats the credit they deserve for being intelligent creatures," Raman said. "They are very smart, good swimmers, good climbers and highly adaptable. They outsmarted us for the first few days."
The trapping operation in Scotch 80s was conducted from Sept. 26 to Oct. 10, with just two rats caught in 119 traps during the first three days.
"We could have walked away at that point and thought there was no problem," Raman said. "But we were suspicious because of the two rats we had trapped, so we decided to change our strategy."
Those changes included creating a "strudel" bait of chopped apples, pears, peanut butter and oatmeal. Northern Nevada officials have had trapping success with licorice and others have reported that hot dogs, dates, peanut butter and professional poison baits have done the job.
The first night the district used its sweet strudel mixture, 10 rats were trapped in the 60 traps that were set along cinderblock walls and other areas where house pets could not gain access, Raman said.
In the end the health district trapped 43 roof rats. Officials called it a significant number, but not a level that would indicate the neighborhood had been overrun, Maxson said.
All of those rats were trapped at night and all outdoors. None of those roof rats had fleas, which carry the plague, but several had tropical rat mites, which do not pose a health threat to humans, Raman said.
Clark County Environmental Health Supervisor Daniel Maxson, who has been trapping rats in Las Vegas for three decades, says, " Basically you see roof rats only at night because they are nocturnal. If you see a significant number of roof rats during the daylight hours, you have been overrun."
Such was the case in the older Arcadia section of central Phoenix, where there are plenty of citrus trees and the rats came out in full force last year, according to published reports in Arizona newspapers.
Both Tempe and Phoenix have begun programs to educate people about preventing roof rat infestation, but last month two Phoenix-area newspapers reported that the roof rat problem had spread to Mesa and Glendale, as well.
The Las Vegas Valley has only seen sporadic colonies of roof rats however. For example, Spanish Trail, a wealthy Las Vegas Valley neighborhood with lots of vegetation, had a roof rat problem in 1998 that has since been neutralized, Maxson said.
And the rodents are not yet posing any health hazards for Las Vegas Valley residents as far as experts can tell.
Since 1993 more than 1,100 rats of all varieties have been trapped in Clark County and tested. So far none of the roof rats caught in Clark County have tested positive for the plague or hantavirus, diseases that can spread to humans. Some indigenous desert wood rats and white-throated wood rats have tested positive for the plague, however.
The concern is that disease will be spread from the indigenous rats to roof rats. And because roof rats are more aggressive than their indigenous cousins and are fonder of lush yards that have plenty of water and food available, they are more likely to come into contact with its human neighbors.
"These animals cannot survive without a lot of water," Maxson said.
Luckily for residents the roof rat prefers trees to homes, and the mild desert winters usually allow them to stay in their preferred habitat year-round.
However, he said, an open door and a ready supply of food will attract roof rats into homes.
"Man and rats have existed together for thousands of years," Maxson said, noting that all humans can do is control the rat's population to make the creature a manageable nuisance.
To that end, Clark County and state officials have taken an aggressive strategy to diminish the rat population. Maxson said area hotels and other businesses that import large numbers of trees for landscaping projects have located and killed roof rats before they established themselves on property.
"In addition to disease control, we are concerned about the roof rat gaining access to food storage areas," Maxson said. "Strip hotels cannot afford to have roof rats gain access to (on-property) warehouses where millions of dollars worth of food is stored."
The health district's policy to return most healthy animals it traps to the wild after testing, but not that's not the policy for roof rats, which serve no useful purpose other than being a link in the food chain.
After euthanizing the rats, the health district tests blood and fecal samples, measures and weighs each specimen and determines its sex.
But trapping and killing alone will not significantly reduce the numbers, experts said.
"We have to take steps to prevent them from coming here," said George Botta, a member of the Nevada Department of Agriculture Board and general manager of American Pest Control in Las Vegas.
"Department of Agriculture (agents) are out stopping trucks headed to local nurseries to make sure they are not bringing in the imported fire ant, roof rat and other things that can cause severe problems. But because of budget limitations, they cannot be out there every day."
Botta said his extermination firm has caught roof rats in various areas of town, including neighborhoods southwest of Tropicana Avenue and Rainbow Boulevard, Rancho Circle and Anthem in Henderson. The habits of the small creatures give exterminators a leg up on killing them.
"They eat twice daily -- just before sunrise and just before sunset -- and they don't travel more than 100 feet in each direction from their nesting area," Botta said. "But they can still find a lot of food, especially in pet dishes. As a last resort they will eat undigested food in pet droppings."
Even if the roof rat's food supply can be reduced, Botta said taking away its water sources is difficult in a community where there are plenty of golf courses, fountains, waterfalls and sprinkler systems,
Richard Hicks, Clark County's vector control officer, said the roof rat's ability to climb makes it a formidable pest.
"People see them walking along the tops of block walls and even along electrical wires," he said. "They can really get around."
Hicks, Botta and others say steps can be taken to make survival more difficult for roof rats:
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