This article is from the March/April 1988 AFRMA Rat & Mouse Tales news-magazine.

By Ed Friedlander, Johnson City, TN, Pathologist, East Tennessee State University

I’d like to share the following account with all breeders.

Dr. Gordon Harrington, who has supplied most of the rats used for psychology experiments, told me several years ago that by far the best pet strain would be his INR, short for Iowa Nonreactive Rat. Of course, these are not available for sale to the public. I read up on the strain, and learned they were bred in 1962 from a stock selected by Hall for low open-field defecation.

I have attempted to duplicate Hall’s work. I founded my colony with the easiest rats to play with from each of six colonies. These were Francis, Gregory, and Fina (pink-eyed white siblings), Theresa (Black Hooded), Martin and Rose (Champagne Hooded, I think), Fabiola (Chocolate), Mariam (Chocolate Hooded, and Patrick (Fawn). Of these, Patrick and Fabiola proved to be the best pets. I handled every adult and kitten briefly every day.

Whenever a litter reached 25 days old, I carried out a selection procedure. Two hours after feeding, I would place each rat in a separate, freshly-cleaned, dry brown plastic bucket. I would observe the rats for fifteen minutes. I would select as breeders for the next generation those rats which did not urinate or defecate during this time (or the last to do so), and which also neither tried very hard to escape (constant jumping) nor cowered in one place without any exploring. If the parents had proved especially gentle and easy to handle, I’d keep two or more breeders from among their children; if not, only one.

During most of this time, I had 12–20 breeding pairs. Originally, one or two in each litter would pass the test. After a few generations, most of the rats from any litter would pass, and from these I would select the best rat to play with, when they were older. I am currently in the eighth generation.

What kind of rats have I obtained? People remark that the younger rats are much more likeable than the originals. They seem to really enjoy being handled, and when I allow them to run freely in my house, they often come up to me and start visiting. Last month I took a load of rats of various ages to visit my best friend from college (now also a physician) who has a rat colony. It was obvious that my selection procedure had produced a rat that is much more at ease around people. I am presently outbreeding my inbred strain, and will continue the selection process as before.

Recently several of my rats (two breeding pairs* and their children, destined for shipment to the University of Minnesota to teach introductory genetics the following morning) were guests at the medical school picnic here in Johnson City. They proved extremely popular, both with the small children and the young physicians. I heard many surprised comments about their gentle disposition, and how they seemed to enjoy being handled. Two of the students asked for pet rats, and both now have breeding pairs (Fawn Hooded) of their own. Both rats and medical students are naturally inquisitive and generally good company.

Of course, any rat’s temperament is a combination of its heredity and its experience. (Lamarkianism is considered refuted, and the parents’ experience should not affect the offspring.) My rats are mostly Fawn Hooded (I think—visitors call them orange, and I call them Tennessee Blaze rats). I am sharing the progress of my experiment not as an advertisement for my animals, but to recommend the selection process itself to all breeders who want to produce the best pets.

* These two breeding pairs have accepted academic appoints at the University of Minnesota, Brookston, MN. They are Tom Becket, a Champagne Hooded buck whose parents were both Fawn Hooded, and his wife Clara, a Pearl doe from California, travelling with their first litter, ten Irish Black and Irish Chocolate kittens.

George Herbert, a Pearl buck, also from California and Clara’s brother, and his wife Elizabeth, an Amber Hooded doe whose grandparents were all Fawn Self or Fawn Hooded, are travelling with their first litter, six Irish Black and Irish Agouti kittens.

These rats are presently travelling by air, in a store-bought plastic dog kennel with its interior entirely covered by metal screen, held in place by duct tape. I have enclosed several points of grapes as a water supply, in addition to more familiar food items.

Of course, one member of each litter is staying behind with me. Several of my new Rex kittens expect to receive similar appointments when they are old enough to travel by air.

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