They cannot be destroyed by nuclear weapons, have few effective predators and by spreading disease may have killed more people than all of man's wars put together.
The fear of the rat, almost as old as fear of the dark, seems to be increasing in Dublin as pest control firms report thriving business. Back in 1977 there were fewer than 10 firms waging war on the rat population in Dublin, now there are almost 40 listed in the Golden Pages alone.
Killing rats has become big business in Dublin for one major reason. An increasingly urbanised population is clearly squeamish at the thought of dealing with rodent problems on their own and like to call in the professionals.
Mr Derek Whelan, of Irish Pest Management, the main contractor for Dublin Corporation, says people nowadays call pest control rapidly if there is a problem.
"Farmers often let rats run around their farm for years without doing anything about them, but the average householder in a town or city wants something done as soon as they see one in their garden," he says.
With some scientists estimating that, on average, there is at least one rat within 20 yards of every human, the chance of encountering the rattus norvegicus is high.
According to Irish zoologists, the recourse to professional pest controllers has increased this summer for two reasons. First, we had a relatively mild winter and the normally high death rate among young rats has reduced dramatically.
Second, the explosion in building activity has caused disruptions to old buildings, and more crucially, to the sewers around the city where rats normally reside in commodious comfort.
Our increasing affluence has sent the number of restaurants and fast-food outlets soaring and man's least favourite rodent cannot help but follow the food trail.
The amount of waste produced by the food industry and ordinary domestic homes provides easy pickings.
In other cities such as New York (where rats are measured in their thousands in the subway) and London, rat populations seem to grow in line with the amount of human waste produced. As Dublin grows and consequently produces more waste and loose food, the rats are likely to increasingly colonise parts of the city.
While humans tend to regard the rat as a dangerous enemy, it likes to cling to human society and has no inhibitions about getting close to us, very close.
Mr Darren Walsh, the head of Omega Pest Control, says he has handled a small number of calls this summer from members of the public who have had close and extremely intimate encounters with rats.
"I have called to a number of houses where rats have appeared in toilet bowls and made their presence felt, shall we say," he says.
While he does not recall anybody being bitten in sensitive areas, the delicate contact made by the rat's tail against their person, not surprisingly, is sufficient to prompt the victim to make a hurried call to the local pest control company.
Mr Walsh says rats have no qualms about entering a house by this route. Attempts to flush the problem away are not always effective as swimming and gripping on to stable objects are two well-honed skills the rodent possesses.
He says the current building boom is the main factor pushing rats into people's homes, via their drains, pipes and any other entry point they can find. The rat's lack of vertebrae means it can squeeze under and through very small holes.
"There are old houses all around Dublin and greenfield sites, both of which are homes for rats. As soon as builders come along and disturb these sites the rats will look for another home and nearby houses and gardens generally provide that opportunity," says Mr Noel Buggy of pest control firm A Bugs Buster. Mr Walsh says his firm has experienced a 10 per cent increase in calls from the public this year compared to 1998.
The disruption caused by building work all over Dublin is spreading the rat population more evenly, according Mr Kieran Carberry, acting principal environmental health officer with the Eastern Health Board (EHB)
Relying on calls to the EHB's pest control unit, Mr Carberry says there has been no discernible increase this summer from the 7,000 "rat sightings" reported last year. However, he points out that sightings have increased since the 1980s. For example, about 5,500 sightings were reported to the board in 1981.
A recent study of 510 wild rats in Oxfordshire found that on average they carried traces of up to 14 diseases capable of being passed on to humans. The study particularly highlighted that two-thirds of the rats were carrying crypto sporidium, a cause of gastro-enteritis.
There is every reason to believe Irish rats carry a similar range of unpleasant conditions, living as many do in the State's Victorian sewers. In the Republic most of the problems have been with the highly dangerous blood poisoning virus, Weils disease. Estimates of how many rats carry this range between 20 and 30 per cent.
Speculation that rats are building up a resistance to ordinary poisons employed against them are described by pest control staff and zoologists as exaggerated. With the rat population apparently increasing over recent years, the uneasy relationship with humans shows no sign of decreasing. Mr Buggy says "people just don't like rats" and their fearful physical characteristics have a lot to do with this.
"I remember dealing with a case several years ago where a builder had been bitten by a rat on the arm. The rat's jaws were so strong that when he bit the builders arm he simply remained locked onto his arm. Other builders killed the rat, but could not get him released from the builders arm," he recalls.
Mr Buggy however rejects the notion of rats deliberately attacking humans. "Self preservation is what they are about, they will always try to escape from humans."