Domestic rats are popular pets in the UK. They are highly intelligent, inquisitive in nature and love exploring their environment. Contrastingly, wild rats are often seen as pests in the environment and not looked upon as favourably by some people. So are they still the same species? Can they interbreed?

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Interestingly the reason we love pet rats is the same reason we are challenged by wild rats. Their explorative nature means they often forage and find all the spare food in the environment. They also gnaw, chew and create tunnels to get where they need to be. This can mean wild rats spend a lot of time around human settlements and can create mess and spread diseases.

What would happen if a wild rat and a pet rat met – can they have babies?

The short answer is yes, they can, but they shouldn’t. 

Pet rats, also known as domesticated rats, are descendants of wild rats which have been bred in captivity and tested for diseases. Breeding them in captivity over generations means pet rats are used to living around humans and their behaviour reflects this. Wild rats are genetically very similar to pet rats; in a similar way to how dog breeds differ, this is how wild and pet rats differ. The key difference is that wild rats carry and transmit a wide range of diseases; and they are not used to living around humans. As a result, they are very fearful and skittish when in human environments.  

If your pet rat bred with a wild rat and then had its babies at home, there is a high chance those babies could be carrying diseases; and that your pet rat may have been infected by diseases when it bred with the wild rat.

Many of the diseases carried by wild rats are zoonotic diseases. This means that the disease is transmissible to humans and can cause disease in humans

Do pet rats and wild rats not have different reproductive systems?

No – they have the same reproductive systems and, as with all rodents, breed all year round. And they are generally very quick to breed when a male and female are put together. They are also genetically almost identical, so there are no barriers to conception. 

What should I do if I am worried my pet rat has bred with a wild rat?

If you believe your pet rat may have mated with a wild rat, you should take your pet rat to your local veterinary surgeon who has experience with rodents. They will be able to examine your rat and, depending on how far along in the pregnancy they are, may be able to diagnose if they are pregnant. Very early pregnancies may not be able to be picked up. They will also be able to discuss disease screening with you, to check if they have contracted any diseases which may be a risk to them or you. They may also be able to advise you on other interventions to end the pregnancy, such as neutering your pet rat.

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How can I prevent my pet rat coming into contact with wild rats?

The best way to prevent wild rats accessing your pet rat is to keep their enclosure in an environment which is not penetrable by wild rodents. An example would be keeping their enclosure inside a designated room in your house; or in a secure outbuilding which does not have holes or areas where rodents could chew through and gain access.

Wild rodents will generally follow food, so keeping the environment clean and tidy, and keeping any food stored in sealed containers off the floor is a good way to prevent rodent pests. It is also important to make sure any rubbish is removed and placed in an external bin as this can also attract wild rodents who love to burrow inside bins as they are warm places to nest in.

Summary:

  • Wild rats and pet rats are able to breed and have babies
  • It is important wild rats and pet rats don’t breed as wild rats carry diseases which can be harmful to pet rats and humans
  • If you think your pet rat has bred with a wild rat it is important to get them seen by your veterinarian as soon as possible
  • It is important to protect your pet rat’s enclosure so wild rats cannot access them

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