INTRODUCTION

Although they are the same from a biological point of view, the ‘wild’ rat and the ‘pet’ rat are very different from each other and this is an important point to bear in mind when we enter the world of rats, either because we intend to breed them and go to exhibitions, or we want to dedicate ourselves to the rescue and subsequent adoption of these friendly animals. 

First of all, we must bear in mind that domestic animals have been (and are) selected for a long time (decades, centuries or millennia in some cases) to live with humans, both benefiting from this relationship.

WHAT ARE THE DIFFERENCES?

A ‘wild’ rat (those that live in cities, subways or open fields), is not and can never be a domestic animal, a ‘pet’; why? 

 As we have mentioned before, the selection of temperament in the ancestors is very important, something that does not happen in ‘wild’ rats, being, as a general rule, extremely aggressive and predatory animals, there being more than one case of good-hearted people who, wanting to help that rat they find in the street, take it home and disaster strikes: ‘hybridisations’ with ‘pet’ rats, attacks, deaths and even cannibalism by the ‘wild’ rat towards the others. 

 In the case of ‘hybridisations’ (not being the most accurate word), we have evidence of a case in which these same offspring, born from an accidental crossbreeding, killed each other when they reached adulthood, something that is very, very rare in ‘domestic’ rats. In this case the instincts and temperaments inherited from the ‘wild’ parent took precedence over the careful selection of the ‘domestic’ branch. 

On the other hand we have the parasitology and diseases that ‘wild’ rats are often carriers of. Unlike ‘pet’ rats, ‘wild’ rats do not have a deworming or monitoring schedule of any kind; parasites such as fleas or ticks can be carriers of diseases such as typhus, plague or ehrlichiosis. In this case ‘wild’ rats are not the culprits, they are the parasites, but they would be the ‘vector’ (the means of transmission) to reach humans and other animal species. Regarding the diseases they can transmit, we can find salmonella, leptospirosis, hantavirus or Weil's disease (which can also be transmitted by ‘wild’ mice); these diseases can be acquired in the following ways:      

-DIRECT CONTACT: Touching ‘wild’ rat/mouse urine or a surface that has had contact with it.

-CONTAMINATED FOOD: These can be contaminated by contact with affected rodents or carriers of these diseases. If we find traces of faeces in drawers or pantries, we must empty them completely, clean them thoroughly and carry out a thorough inspection of all containers, discarding all those that have been nibbled, as we may be facing an infection. 

-CONTAMINATED AIR: In the event that we have to access closed places (attics, attics, cellars...) that are not frequently visited, we must access them with a mask and try to ventilate for at least one hour, as urine vapours or dust can remain suspended in the air.

-OPEN WOUNDS: If we have a wound that has not yet closed and comes into contact with the urine of an infected rodent, we can expose ourselves to a serious situation.

It is for these reasons that we should knowingly refrain from contact with ‘wild’ rats, as they are not only a danger to us but to our own rats. Feral’ rat infestations are also an environmental and health hazard for the reasons mentioned above, where urban “CES” (Catch -> Neuter -> Release) cat colonies play a very important role, as well as cats living in semi-free or total freedom in rural areas, as they prevent uncontrolled breeding by hunting. 

WHAT SHOULD I DO IF I FIND AN ABANDONED RAT?

The first thing to be sure of is that it is a domestic rat; there are many requests for help from animal shelters that take in this type of animal and, in truth, they are wild rats that are simply living their lives. In the case of a wild rat, the first thing to do is not to intervene or bother it unless it is in a situation of real danger (wounds, illness...); normally, a wild rat in good condition will run away when it sees us. 

To catch it, wear thick gloves and use a blanket or cloth (also of a certain thickness) and put it in a carrier or box that we will keep as dark as possible, in this way the animal will be calm and we will prevent it from becoming more stressed than it already is. After the visit to the vet (and if it does not have to be admitted) we will put the rat in a separate room where no one else enters except us, keeping the minimum contact with it (just enough to feed, clean or cure) and taking all the necessary hygiene measures, including gloves and a mask (some people add protective goggles to avoid contact with the eyes from vapours, dust or debris that may fly). 

Once the animal has recovered, it should NEVER remain in captivity, but should be released in the same place where it was found, as this is its ‘comfort zone’, where it will feel safe and will know how to find its way back to its family. 

In the case of finding a nursing rat or a litter we should never touch them, most probably the mother will be nearby, watching our movements and waiting for the right moment to pick them up and take them away; if even with that we are not reassured it is best to leave and return after this time, if the young are still there then we can pick them up (taking the necessary hygienic measures) and we will go to a vet. 

This ‘action of mercy’ can be a double-edged sword, on the one hand it is likely that these animals (if they are too young) will be ‘imported’ (we will explain this term later) and remain in a state of ‘no man's land’ as they cannot be released or tamed, turning their life into an accumulation of stress. On the other hand, a wild animal forced to live in captivity may die due to the same stress.

CONCLUSION

Domestic and wild rats have many similarities but their differences are enormous, especially when it comes to health. We must not forget that a rat born in captivity and bred correctly, which is in good health, cannot infect us with anything, but this is not the case with wild rats, so we must take great precautions and not run unnecessary risks.