Pick up any text book that talks about the arrival of the rat (either species) into the UK and you tend to get the same answer. For the Black rat this is the 12th C, following on from the Crusades, and the 18thC for the Brown. The evidence for both these dates is backed up by only sketchy anecdotal evidence, which we will see. The problem with anecdote is that it is frequently wrong. Anecdote has given us mermaids and little green men. Of course, some anecdotes are proved correct, but they need to be backed up by fact, preferably in the form of bodies! This is one reason why naturalists were so keen on collecting specimens. Another problem is that before the Swiss naturalist Linnaeus in the 1730s, started up the now familiar process of giving everything a Latin name, there was no firm method of classification. A rat in much of literature was just a small animal, and was not differentiated from a mouse. Often just local names would be used, which had no meaning outside of the immediate area. This is still a problem now where common, as opposed to Latin, names are used. For instance, I did some bird watching in France, and while I could work out that a Heron Garde-boeufs was a Cattle Egret, I had to rely on the picture to work out that a Busard Saint Martin was a Hen harrier.
In 1553, a German Naturalist named Konrad Gesner wrote his epic book 'Historiae Animalium'. An amazing book that is now available online. This attempted to name and describe all the animals known at the time. The books included illustrations and any previous knowledge on the species concerned; in short, the first natural history on all known species and definitely a work of art!
Gesner was not that selective in the animals he included and indeed there are a fair selection of animals that we would call 'mythical' now, such as a unicorn and a dragon. The illustration of the rat included in this book has often been said to look more like a brown than a black rat. However, seeing as the drawings in the book are not exactly scientific illustrations, I would take that with a pinch of salt. Basically, it could be either, although it is obviously a rat.
There isn’t as far as I am aware an official translation of Gesner’s work available into English although a German translation was published in 1667. Edward Topsell's 'History of the Four Footed Beastes' is said to be an English copy of Gesner's work but as a copy is not available online I can't say. However, an American NFRS member, Alan Gangi, has had a partial translation of the rat page done for me.
The rat section contains quite a lot of information on the problems Gesner found identifying the rat in old literature due to its lack of a formal name. In fact, he points out that while at the time he was writing most of Europe was using the word 'rat', Germany were referring to rats as 'the greater domestic mouse', and in fact he calls his rat chapter 'de mure domestico majore'. Among the names that rats had gone by in antiquity Gesner lists, mouse, cobweb mouse, hydrax (also meaning mouse) and colotes (also Greek for lizard). All of the traditional writers, Pliny etc, seem to have used a different name, most likely a local one.
In fact, it took a while for things to sort themselves out. Four different naturalists separately classified the Genus Rattus using modern Latin naming methods, so you can still find the rat referred to in several ways in older works. The rules of naming living things however, decree that the first person to name them takes the honours, unless there is a good scientific reason why this first name is later considered incorrect. That is why the Brontosaurus that we remember from our childhood is now called Apatosaurus, because some years ago, after we all got used to Brontosaurus, some one found an old fossil bone of Brontosaurus labelled with the older name!
The first naturalist to formally name the Brown rat was John Berkenhout in 1769. He used rats found in Britain and coined the present name Rattus norvegicus. However, the Norwegian naturalist Erxleben named the rat, Mus norvegicus, in 1777, using Norwegian rats, for quite a long time, people thought that they were different species. The rat was further classified by the German naturalist Pallas, in 1778, as Mus decumanus, (large mouse) when he was working in Sweden. Pallas was a renowned scientist of the time so not surprisingly this name stuck until well into the 20th Century in some quarters. Certainly the early rat fancy used it when writing in Fur and Feather. The name Rattus did not meet with universal approval or maybe it had been forgotten about, because in 1881 Trouessart named all the larger Mus species as Epimys. However, this term had been largely dropped by 1913, when it was pointed out that Rattus was the original name. Apart from the variation in the Genus name, the Brown rat is also recorded with a host of species names, including albinus, albus (for white rats), hibernicus (rats with white bellies, first seen in Ireland), aquaticus, americanus, caspius etc. All of these names however are just variants of the Brown Rat and are now defunct.
As we have already said, the dates of 12th and 18th C are fairly well established in the literature. In ' The Laboratory Rat', (2005), the arrival of the Brown rat is given as 1728-1730, a date that is widely quoted elsewhere. The reason for this isn't entirely clear, but it was believed to be tied in with the arrival of Russian fleets from the Baltic and rats being noticed in large numbers in some areas. Most reference works mention that this date is 'well documented' without giving any references and I have not been able to find them. There is mention of a writer named Donndorff (1792), and another called Pennant who in the early 1760's wrote that the first brown rats reached England 'about 40 years ago'. Whether information written so long after the event can be considered to be reliable is open to question however, neither is it made clear why the Brown rat should suddenly have made its appearance all over the place in large numbers. The date has been linked by many people to an invasion of rodents of all sorts that crossed the Volga in 1727, following on from a massive earthquake. However such invasions had been noted before, including by a writer in the 2nd C. Rodents are prone to explosive population growth and migrations, it’s where the myth of the suicidal lemmings comes from.
Not all writers believed this date however. The father of the Naturalist Charles Waterton, for instance was convinced that the Brown rat came over with George 1st in 1714. This was believed largely because both George 1st and the brown rat were very unpopular. It’s also where the brown rat gets the title 'Hanoverian rat'. Interestingly his son (Charles Waterton, Essays on Natural History), reported that the Brown rat came over with William of Orange, another unpopular monarch, in 1688. Yet another theory, written by an American Scholar Alfred Henry Miles in 1895, links the arrival to trade with Central Asia from the end of the 17th C. One thing is certain however, and that is the Brown rat did not come from Norway. The Brown rat is not known to have reached there until 1762.
Good old Gesner in his Historiae Animalium does come up with an interesting point however, although he is writing about Germany and not England. He reports seeing a white rat with red eyes. Now this mutation is not present in Rattus rattus but most certainly is in norvegicus.
The reason that the Black rat is tied to the 12thC appears to be due to the monk Giraldus Cambrensis, who wrote about 'mures' (another name linked to rats and mice) and 'the larger mice that are commonly called rats'. This was written around 1190, although the exact date is unsure. There is no positive evidence (ie reports) that the Black rat did come in with the Crusades however. Since he mentions that these animals were ‘commonly called mice’, it seems reasonable to assume that rats were well known by 1190, not that they had just arrived.
Rodents are believed to have originated in Asia. They make their first appearance on the fossil record around 54 million years ago. These original rodents were themselves descended from the Anagalids, who also gave rise to the rabbits and hares. The ancestors of the Murid rodents, which include rats, hamsters, mice, voles and gerbils, first appeared about 34 million years ago. From here, by examining mutations in the DNA of modern animals, rats and mice are believed to have diverged about 10-12 million years ago, and the black from the brown about two million years ago. Today there are at least 64 (possibly double that) species of Rattus and DNA evidence has shown that they are evolving faster than mice or humans, which are two other groups showing rapid change.
Oddly much more is known about the origins of the Black rat (Rattus rattus) than the Brown. It's known that it originated from India and the Asian subcontinent where it is still the dominant species. It’s also known from skeletal remains that it was fairly common in many parts of Europe between ice ages. Remains have been found in Germany, France, Italy and Crete. Europe was much hotter during these periods however and the Black rat prefers it warmer. At the time the UK was not separate from Europe so it may well have been here as well but I have not found any reports for this. As far as I know, there are no records for this species being present during the various Ice ages, but absence of evidence is not evidence of absence, and rodents don’t make good skeletons.
Lots of authors (including a guy called Shewsbury, who wrote a lot on the Black Death) continually quote that as there was no separate word for rats and mice; that it was unlikely that the Greeks and Romans were acquainted with the rat. However, works of art including animals that look very like rats do exist from this time, including a gold coin with a depiction of the God Apollo and a rat, and a number of votive offerings. In 1924, a Dr Sambon wrote about this in the Journal of Tropical Medicine and Hygiene, so none of this is exactly new. There were also several outbreaks of a disease that sounds very like bubonic plague from the descriptions. One is mentioned in the Old Testament, where the Philistines were 'smitten with Emerods' (buboes) and a really terrible outbreak during the time of the Emperor Justinian in 542 AD where around 50% of the city of Constantinople were said to have died.
More importantly the bones of Black rats have been excavated from sites all over the old Roman empire including Corsica (4th - 2nd C BC), the ruins of Pompeii, London (3rd C AD) and York 5thC AD. You do have to be a bit careful with archaeological evidence however, as disturbance of levels does often occur, meaning that objects can become misclassified.
It’s odd that so little is known of the natural origins of the Brown rat, bearing in mind how widespread it is. Using DNA analysis, its closest relative is Rattus moluccarius (also called Rattus masaretes) an inhabitant of several Indonesian islands. Some text books give out five other sub species. Although modern research has indicated that these are not valid and there are no subspecies of Rattus norvegicus, the taxonomy of the Rattus group is in a state of flux and is perhaps surprisingly the subject of a lot of research, due to their economic interest and rapid evolution. South East Asia is the hot spot for most of this.
The original wild rat is believed to have originated on the plains of Northern China and Mongolia, where wild rats still live in burrows today, but this is not confirmed.
With the exception of Gesner's albino rat, the earliest anecdotal evidence for the arrival of the Brown rat into Europe is 1688, and even that probably has more to do with political slur than fact. Rats are not large or conspicuous animals and it would be surprising if anyone noticed a different species until the numbers got quite high. Black rats are also quite often agouti and Brown rats quite often black. There has been an assumption by archaeologists undoubtedly keen to save a bit of money that any rat bones found in digs prior to 1728 were Black rats, meaning that bones are not normally properly examined. However, Brown rat bones have been found at the medieval settlement of Klein Freden near Salzgitter in Northern Germany, which was occupied from the 9th to the 13thC AD, and at Bodenteich Castle, Lower Saxony, also from the medieval period. Furthermore there are a few instances of Brown rat bones being found in English archaeological sites, namely Medieval Jarrow and Skeldergate, York early 15thC. It would appear that, like the Black rat, the date that the Brown rat first turned up in these Isles is unknown. Its also interesting that Black rats were said to be bigger prior to the arrival of the Brown rat, this has been put down to greater competition, but could just as easily be due to misidentification.
It’s easy to jump to conclusions when it comes to the decline of the Black rat and the increase in numbers of the Brown. For instance, there is the often quoted anecdote from Princess Amelia’s rat catcher in 1768:
"The black ones do not burrow and run into shores as the others do but chiefly lie in the ceilings and wainscots in houses, and in outhouses they lie under the ridge tiles, and behind the rafters, and run about the side plates; but their numbers are greatly diminished to what they were formerly, not many of them being now left, for the Norway rats always drive them out and kill them wherever they can come at them; as proof of which I was once exercising my employment at a gentleman’s house, and when the night came that I appointed to catch, I set all my traps going as usual, and in the lower part of the house in the cellars I caught the Norway rats, but in the upper part of the house I took nothing but black rats. I then put them together into a great cage to keep them alive until the morning, that the gentleman might see them, when the Norway rats killed the black rats immediately and devoured them in my presence."
Now, this doesn’t seem surprising to me. If you place animals together in a cage where they can’t get away from each other then this is not unexpected. As Jack Black noted later, this happened when he caged Brown rats together as well.
Black rats are more agile than brown rats and better climbers, having said that, Brown rats can often be found in roof spaces and black rats in burrows. Certainly the black rats on Lundy Island inhabited the rabbit and puffin burrows. It’s hard to say where the black rats of antiquity lived, but it would seem logical that thatched roofs would have provided good nesting sites, as would hay ricks and feed stores.
It’s also interesting to note that the black rat has been reported as being on the verge of extinction in the UK for about 200 years, and somehow it is still here. It still lives on some offshore islands, and in parts of London, and here and there around the rest of the Country. In most areas, it seems to live alongside the Brown ones.
There is no doubt that the Black rat did decline in numbers as the Brown rat increased, but the real reason why is not straightforward. It seems likely that a combination of factors were responsible.