This article is from the WSSF 2007 AFRMA Rat & Mouse Tales news-magazine.

Question posed by an Orange County fair-goer at our display
Q Why was Rattus norvegicus (Norway rats) domesticated and not Rattus rattus (Black rat)? Why did labs take on the Norway rat for research instead of the Rattus rattus rat?

Answer by Carmen Jane Booth, D.V.M., Ph.D.
A I couldn’t find a published answer for this question. Neither species was native to Europe or France. My suspicion is that Rattus norvegicus may have out-competed Rattus rattus. I believe, but do not have documentation to support that, the Norwegian rat is still more prevalent then the Black rat. I have never worked with R. rattus either wild nor domesticated, so I cannot comment on the temperament once domesticated. What I could find out was that the first rats that were domesticated were probably albino R. norvegicus. Rat baiting was common in England and France in the early 1800s and subsequently in America. As a component of this “sport,” the Norway rats had to be trapped and held to be ready for the contests. Records indicate that albinos were removed and kept for shows and breeding. Thus, it was concluded that with frequent handling, these rats became tame and ended up eventually in research (and the pet trade).

Reference: Richter, C.P. (1954) The effects of domestication and selection on the behavior of the Norway rat. J. National Cancer Institute 15,727-738 taken from Pathology of the Fischer Rat, Reference and Atlas edited by Gary A. Boorman et al. 1990 Academic Press, Inc., page 5.

Answer by Nichole Royer
A The simple answer is that when born in captivity and handled/ tamed young, Rattus norvegicus is relatively docile and make nice pets. Not saying that they act like our “many generation” domestic rats, however, they are fairly tame. They are a fairly mellow species to start with and tend to be rather bold. Wild Norway rats often come into fairly close contact with humans in their natural habitat. Rattus rattus, on the other hand, is a much flightier species. They remain so, even with early handling. They are much shyer in the wild, and much more secret in their habits. Thus, they are much more difficult to “tame.”

Answer by Karen Robbins
A In the 1800s when they began showing rats, there was mention of Rattus Rattus type rats being shown but the Rattus norvegicus ended up taking over what people ended up with for breeding and show purposes. From what I’ve seen of the wild black rats that people have taken in as pinkies and raised on domestic rats, they don’t like to be held even though they had lots of handling when little. They would come out of their cage onto the owner’s arm and walk around but would not like to be picked up by their body or be held. I’ve seen this numerous times over the years with different people and always the same reaction with the rats. I’ve only heard of one person that had a wild rat that she could actually hold when it was an older rat.

There is a web site of a lady in England that is working with the black rats http://members.madasafish.com/~cj_whitehound/Rats_Nest/Ship_Rats/Menu.htm who has lots of information on them. From what she says, it reminds me of a horse versus a zebra—the horse is domesticated, the zebra is not.

Debbie Brown, e-mail
Q I read in “Kid’s Basic Care for Rats and Mice” that they like to eat celery. We were told by the local pet store never to give our rat celery because they can’t digest the strings and they will entangle their intestines.

Answer by Carmen Jane Booth, D.V.M., Ph.D.
A I don’t think that this is uniformly true. Rats can eat just about anything they can get their teeth into. However, feeding celery is not really suggested because it has no nutritional value and is a known carcinogen in rodents. Unfortunately, many of our “healthy foods” contain naturally occurring mutagens or carcinogens that are known to cause cancer in rats, largely in part due to their shortened lifespan. There are numerous websites that list foods that are known to be carcinogenic in rodents. Each owner has to make their own decision regarding risk.

I pretty much stick to a formulated lab-block diet with supplements of dried grains, beans, rice, and fresh rinsed fruit and veggies that my rats enjoy.

Websites of interest:

• for the article “Naturally occurring mutagens and carcinogens found in foods and beverages” by the American Council on Science and Health, published in Environment News, November 1, 2002, by the Heartland Institute.
• www.garfield.library.upenn.edu/papers/vethumtoxicology31(6)p589y1989.html for the article “Man-made and natural carcinogens—putting the risks in perspective” by Eugene Garfield, Veterinary and Human Toxicology, 31 (6) p.589–590, 1989.

Back to top