companion for my rat

Question
We had two beautiful 15 month old females, sisters who had been together since birth. Yesterday, one passed away from illness. I am wondering what you think might be the psycholgical impact on the survivor, and how we might mitigate that? I would also like your thoughts on whether it is a good idea or even feasible to successfully introduce a new companion. If so, is there an amount of time we should wait before trying, and what are some of the other important considerations for giving them the best shot at compatibility? Thank you.

Answer
Hi Don

I am sorry for the loss of your girl. I hope your heart heals fast.
Its always so hard to lose them, especially at this age. She was still young yet!

Unfortunately, the psychological impact is pretty strong when a rat loses its cagemate and it can actually cause her stress to the point her immune system becomes fragile and she can become susceptible to illness herself. I have seen it happen dozens of times including my own rats. Rats are very social animals and take great pride in living in a mischief (rat colony) The mourn the death of their cagemate by becoming depressed, loss of appetite, sleeping more often etc...and become lonely too. No matter how much attention you give your lone rat, its not the same, of course, as having your own species to snuggle with, grooming each other and just simply keeping each other company.
Females seem to welcome a new cagemate better than males do (its that testosterone thing I suppose, lol) and its usually not a problem getting the existing rat to welcome an outsider. They are curious and nosey by nature (especially females) so expect alot of sniffing and possibly even a bit of rough housing by pinning each other down to sniff each other. Just by smell, rats can tell the age, sex and even what the rat has recently eaten!  Did you ever sneak and give just one of the rats a treat (say, the other one was still snoozing) and if the other rat wakes up, she would immediately go to the other rat, sniff her face and SULK because she missed out on the treat? Its pretty comical to see how smart they are. I have done extensive studying on rodent behavior and the rat is by far the most intelligent and clever of them all!
You may not welcome my suggestion, however. Remember, its just a suggestion:) I usually suggest two new rats, especially if they will be younger than the existing rat, because if not, you will find yourself in the same cycle should the older rat pass away within the next XYZ months and the newest rat will find herself alone. Unfortunately the cycle of owning rats never seems to end once you start unless you just decide you want to stop keeping them which as you would probably agree, is pretty hard since they are such sweet little pets.
Having two younger female rats are better because the existing rat is older and she may not appreciate the younger rats energy and may not be up to wanting to chase and play fight since she is beyond that stage and is close to menopause herself (around 18 months and older)
Of course the choice is yours, but either way, I do strongly suggest at least one female for her and if you want one closer to her age, you can check into local shelters. There are often rats that sit there for months waiting for a home that never comes to pass.

Keep in mind you must do at least a 3 week quarantine depending on where you live (if your in the US or not, that is) and after that, proper introductions should be done so you introduce the girls gradually. I suggest after the time has passed for quarantine, keep the cages side by side and allow them to get used to the fact there is another rat around. A few days of that and you can take them out to play, holding either the new rat or the existing rat and allowing the other rat to smell her and get used to her.

In closing, you asked how long you should wait before getting another rat (or rats :) and I would say I would start looking right away.
I am not sure if you purchased your rat from a pet store or not but if so, I also suggest trying to find a reputable breeder in your area that breeds rats. Unless the pet store is remarkable, they do not get their stock from very reputable breeders and in fact are often breeder mills that breed hundreds at a time, often for feeders, and are not properly socialized nor are they bred for health. A good breeder knows to socialize the newborn pups often from the second day they are born so they are not skittish and also keep track of their lineage so they know their health history through the generations. Breeders should never breed from aggressive or rats that have had offspring that have died young from congenital defects such as heart, kidney or liver disease although this cant always be avoided later in life and sometimes these things develop because of poor care (diet, lack of medical attention etc) and although I am more of the "rescue" type person, I know how hard it is to find rat rescues. I lean more toward dog and cat rescue which of course there are plenty of them at the dog pound and other animal shelters.

SO, thats it in a nutshell.  Hope you dont mind my mini novel. I tend to over extend my messages a bit but most of the readers dont seem to mind. :)

Hope to hear from you soon and I if you need more help, just give me a yell!

Sandra