You may be familiar with Jean de La Fontaine’s fable entitled The city rat and the field rat ? The classical poet uses these two animals to compare city and country life. Beyond their different living environment, are these two animals two separate species? And if so, how can we tell them apart? Our article gives you all the details.
Two species of rats belonging to two different genera
The field rat and the city rat are both rodents of the murine family, such as mice or gerbils. Within this family, we find the kind Rattus which has, in the current state of knowledge, more than sixty species, most of which live in Southeast Asia, Indonesia, Papua New Guinea and Australia. They can all be called “rats”.
In Europe, we mainly have the field rat and the city rat. The first has the scientific name rattus rattus and can also be called black rat or attic rat. The second is a different species: it is the rattus norvegicus, also called brown rat, sewer rat, gray rat or brown rat. The latter invaded Europe during the 18th century, later than the field rat which was present there before him. The city rat then invaded the cities, relegating the field rat to the suburbs and parks. In the countryside, however, the field rat retained its supremacy, quite simply because it was better adapted to this type of environment. Scientists have shown that these two species are not at all closely related, with the closest species to the city rat being the rattus nitidus.
The differences in appearance between field rats and city rats
You might be wondering if it’s possible to visually tell the difference between these two rat species if you cross them. This is absolutely the case because they have very distinct morphologies.
The field rat first undoubtedly has a slimmer silhouette than that of the city rat. Its tail, which measures between 20 and 25 cm, is a little longer than its body, whose length varies between 15 and 20 cm. The silhouette of the city rat, on the contrary, is more enveloped. Its tail is almost as long as its body and is thicker than that of the field rat. The two species reach weights that are without comparison: the field rat oscillates between 75 and 230 g while the weight of the city rat varies between 250 and 500g, with a big difference between males and females for the latter.
Their heads are also quite different in profile: the field rat’s ears are quite large in proportion to the rest of the head, as are its eyes. In city rats, the ears and eyes are proportionately small. Finally, the muzzle of the field rat has a pointed profile while that of the city rat is thicker.
Distinguishing them on the sole difference in their coat is quite difficult. The color of the belly is lighter in field rats.
On the other hand, if you have the possibility of observing these rats a little more closely, you could know for sure which it is according to the number of toes on their legs: the field rat does not have the same number of fingers between the front legs (4) and the rear legs (5), while the city rat has 5 toes on each of its legs. Their number of udders also differ: a female field rat has 5 while a female city rat has 6.
Behavioral differences between field rats and city rats
Both rat species mostly live at night, but the field rat has good eyesight while the city rat sees poorly, making more use of its sense of smell. The first prefers to feed on seeds while the second has developed a very feeding behavior. opportunistic, approaching the human diet and preferring meat when it is available.
Field rats don’t like humidity. It is therefore found under bushes or settles in height by climbing in trees or by accessing attics and under the roofs of houses. He lives in small groups of about fifty individuals.
The city rat, on the contrary, seeks humidity. It digs tunnels or lives in caves or sewers, and builds its nests with recovered materials. It is a very good swimmer and settles its colonies near a water point. These can reach several thousand individuals, which requires them to be structured into clans organized in a very hierarchical manner. He has developed a very aggressive behavior and proves to be a formidable fighter, even when he has to face animals much larger than himself. Rats have been seen attacking piglets, lambs, poultry and even humans. Is it for this reason that he can hope to live from 2 to 3 years when the field rat can only hope to live one year?
Rats and men
Rats have always been around people and proliferate alongside them. Today, the two populations are equivalent: there are 5 billion men but also 5 billion rats. Every human could have his rat …
The rat, whether it is fields or cities, is very prolific: a single female can give birth to about sixty young each year. A rat population is multiplied by 3 in just 8 weeks. Thus, in the absence of predators or human intervention, rat colonies grow exponentially.
This proliferation is of course not without its problems. The rat threatens the presence of certain animal species, taking the place of rodents less competitive than it. Cohabitation with humans is far from peaceful since both species of rats are pillagers, whether they are crops and food reserves for field rats, or warehouses and stores for city rats. Both also attack the sheaths of electric wires and insulation materials, thus creating many problems, as much in isolated rural houses as within the electrical or telecommunications networks that stretch into sub-areas. soils of our cities.
Obviously, how can we not talk about rats without mentioning the many diseases transmissible to humans that they carry. Among them, the plague is the most feared: the 3 major pandemics that have decimated Europe have left heavy traces in history. It is still endemic in parts of Asia and Africa (notably Madagascar). It should be noted, however, without changing the result, that this terrible disease is actually carried by the fleas of rats and not by the rats themselves.
In western cities, rats mainly carry bacterial diseases such as leptospirosis and salmonellosis. Leptospirosis is transmitted through the droppings of rats and causes 1 million severe cases each year worldwide, 10% of which are fatal. As for salmonellosis, 3.4 million sufferers are identified worldwide, more than 600,000 of whom die. This situation justifies a constant effort to contain rat populations. Children and fragile people must absolutely avoid contact with them.
Rats are therefore harmful. Despite everything, they prove to be invaluable aids in the management of human waste, by playing the role of natural garbage collectors. It is estimated, for example, that in Paris, rats consume around 800 tonnes of waste every day, or more than a third of what human garbage collectors collect. They also contribute to the regular cleaning of sewers, avoiding their clogging and saving money on cleaning operations.