People ask whether rats are a problem in the UK? The simple answer is yes. The brown (Rattus norvegicus) and black (Rattus rattus ) rats are the only two species in the UK if we ignore the number of exotic rodents being bred here and just concentrate on the wild ones. We can only estimate so a figure may be exaggerated but the one seemingly accepted is a population of 250 million.
Even with a suggested lifespan of only 2-3 years a female rat typically births six litters a year consisting of up to 12 rat pups, although 5-10 pups are more common. Rats reach sexual maturity after nine weeks, meaning that a population can swell from two rats to around 1,250 in one year, with the potential to grow exponentially.
The natural predator of the rat in the countryside, villages, towns and cities are the cat (these days feral cats probably take more rats than pet cats) and the fox. Owls and hawks will also take rats and this is where the problems begin for wildlife because the solution of most local authorities is to use rodenticides and secondary poisoning of predators is a major problem.
If you listen to pest control companies, who have a large financial interest in the matter, rodenticides are the best solution. I have had three pest control officers from Bristol tell me to my face that the poison they use does not affect wildlife and no other animal can be affected by ingesting poisoned rats. An outright lie. By supermarkets and shops you tend to see metal boxes attached to lamp posts and these are designed so that if the rat enters it is "zapped" and killed.
There is one shopping area near me where these traps are always smashed. I found out that locals were doing this as curious small birds were entering the traps and being killed and the final straw was an electrocuted hedgehog. Figures on small wildlife killed by these traps is not available and if you try to search for that information all you will get is page after page of pest control adverts, recommendations. People on The Red Island tend not to care because "out of sight out of mind".
There are various mouse and rat traps that can maim and leave a rodents to die slowly and the larger traps, as with the "zappers" and these are again deadly to small mammals.
Back in the 1970s I was reading in a German magazine how a small town had cut its rat population right down and I guessed more poisoning and trapping but I was wrong. Someone had suggested, and the local authority approved the idea, that bait with some chemical in it be placed out for rats and the chemical was a contraceptive one. I have tried over the years to find the article or the town and failed -even with the internet. The question is whether it is better to sell off the shelf rodenticides to the public who have no idea how to use it or for local authorities to employ pest control people who then use rodenticide or use something that will affect the rats and no other wildlife?
Yes, pest controllers are heavily invested in the use of poisons so that would affect their livelihood but at this point in time we have to start thinking about wildlife which is being killed in droves as well as the effect on the environment. I have already discussed elsewhere how you can get rats out of your home without poison here
https://athomewithwildnature.blogspot.com/2021/05/so-lets-talk-about-rats.html
And research work has been carried out of how to use a contraceptive in bait to deal with rodents and there is a paper on the matter -Fertility Control for Wildlife: A European Perspective by Giovanna Massei https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9913817/
Quote:
"ContraPest® is a liquid contraceptive designed to reduce fertility in rats and delivered in a tray, placed inside a box, to minimise use by non-target species [78]. ContraPest suppresses fertility in males, by preventing sperm maturation and motility, and in females, by decreasing the number of eggs that are ovulated [79,80]. This contraceptive must be delivered daily for at least 50 days in order to inhibit production of litters for around three successive breeding rounds, as shown in captive studies with Norway rats [81,82]. In this species ContraPest decreased the weight of reproductive organs but had no effect on adrenal, kidney, spleen and liver weights compared to control animals [82]. The efficacy and potential side effects of ContraPest on free-living rats has not been reported, as only information on the efficacy of ContraPest combined with a rodenticide is available [78].
"EP-1, based on synthetic steroids, has been proved to inhibit the fertility of males and females of many rodent species in China, Tanzania, Zambia, and Indonesia [83,84,85,86,87] in captivity and field trials. In several species, a treatment period of about 7 days in laboratory studies or a single baiting with EP-1 in field conditions, are sufficient to induce infertility [87]. In females the most common response to EP-1 is an enlargement of the uterus which result in reduced conceptions and/or litter sizes. In males EP-1 inhibits the function of the testis, epididymis and seminal vesicles for different periods of time depending on the dose [75,87] and in both sexes the effects are temporary and fully reversible. Side effects of these synthetic hormones in rodents include production of smaller pups in striped field mice (Apodemus agrarius) dosed with EP-1 [88] and in Brandt’s vole (Lasiopodomys brandtii) treated with quinestrol [74]. EP-1, widely tested on many rodent species, has not been used in field trials in Europe and its use might not be acceptable until the potential effects of the hormones on the food chain and on the environment have been assessed."
References cited
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